Thomas Bolognesi

Modernisation of urban water services management in Europe and prospects for sustainability An analysis in terms of institutional resource regimes

Keywords: Institutional economics, Sustainability, Water management, Europe, Cities. JEL classification: O17, P48, Q01, Q25, R11

This article assesses the sustainability potential of the urban water sector in Europe following its modernisation. The analysis uses the theoretical framework of institutional resource regimes. This interpretative framework provides us with a typology of natural resource governance systems based on their coherence and their extent. Then, based on the interplay of hypothesis and conjecture, the framework is used to deduce the capacity of a regime to provide sustainable governance. We conclude that modernisation offers a path for progress which though necessary is not sufficient. This pessimistic assessment is based mainly on the observation of a lack of coherence in urban water systems in Europe. The study is divided into three parts: description of the modernisation process; presentation of the interpretative framework used in analysing institutional resource regimes; application of the framework to the urban water sector in Europe.

Institutions play a determining role in the performance of a particular economic sector. The modernisation of the urban water sector in Europe provides an example of a regulation/re-regulation process implemented within an institutional framework. This case is specific because of a strong environmental constraint on the governance process. It offers an illustration where governance and sustainability meet.

More precisely, public authorities provide urban water governance through standards and public policies. Analysis of this governance has already led to the definition of a European model of water management and the identification of its constituent parts in terms of national variations (Correia, 1998;[START_REF] Finger | Water and Liberalisation: European Water Scenarios[END_REF][START_REF] Grossi | Comparative aspects of Institutional Variants for Local Public Services Provision[END_REF][START_REF] Ménard | Liberalization in the Water Sector: Three Leading Models[END_REF]. For two decades, this institutional framework has been evolving in order to meet the requirements of the sustainability objective [START_REF] Kallis | The EU Water Framework Directive: Measures and Implications[END_REF][START_REF] Barraqué | Past and Future Sustainability of Water Policy in Europe[END_REF][START_REF] Garin | Why are there so Few Cooperative Agreements between Farmers and Water Services in France? Water Policies and the Problem of Land Use Rights[END_REF][START_REF] Wright | Operationalising Active Involvement in the EU Water Framework Directive: Why, When and How?[END_REF]. Instrumental in this institutional change has been the emergence of new technical standards, the Urban Waste Water Treatment Directive (UWWTD), and the Water Framework Directive (WFD). Following this re-regulation of the urban water sector, the question of the effectiveness of these changes needs to be examined. To gain insights in this area we adopt an approach in terms of urban water systems in Europe (UWSE), which provides us with a broader subject of study than the classic definition of the urban water sector used in economics (Bolognesi, 2012). A UWSE provides a means of interaction between the stakeholders in an urban water cycle and the institutions that coordinate them. This approach puts the institutional dimension of governance at the heart of the system and takes into account the interactions between the standard economic characteristics and the institutional components.

The approaches used in rational choice institutionalism provide an analytical framework capable of taking these interactions into account but they avoid the conflict dimension of urban water uses and do not adequately address the question of sustainability [START_REF] Ostrom | Governing the Commons: the Evolution of Institutions for Collective Actions[END_REF][START_REF] Ostrom | Institutional Incentives and Sustainable Development: Infrastructure Policies in Perspective[END_REF][START_REF] Saleth | The Institutional Economics of Water: A Cross-Country Analysis of Institutions and Performance[END_REF][START_REF] Lorrain | Urban Capitalisms: European Models in Competition[END_REF], 2008;[START_REF] Ménard | Liberalization in the Water Sector: Three Leading Models[END_REF]. The approaches adopted in historical and/or sociological institutionalism reintegrate conflictual aspects into the analysis but their contingency dimension reduces the predictive power of the results [START_REF] Aguilera-Klink | Introduction[END_REF][START_REF] Zuindeau | Régulation School and Environment: Theoretical Proposals and Avenues of Research[END_REF][START_REF] Renou | The Governance of Water Services in Developing Countries: an Analysis in Terms of Action Stratification[END_REF]. We therefore use an alternative approach based on institutional resource regimes (IRR) that has been developed with a view to determining the potential for sustainability of regulation of natural resources (Kissling-Näf and Kuks, 2004;[START_REF] Knoepfel | Régimes institutionnels de ressources naturelles: analyse comparée du sol, de l'eau et de la forêt[END_REF][START_REF] Gerber | Institutional Resource Regimes: Towards Sustainability through the Combination of Property-Rights Theory and Policy Analysis[END_REF][START_REF] Garin | Why are there so Few Cooperative Agreements between Farmers and Water Services in France? Water Policies and the Problem of Land Use Rights[END_REF]. This interpretative framework provides us with a typology of natural resource governance systems based on their coherence and their extent. Then, based on the interplay of hypothesis and conjecture, the framework is used to deduce the capacity of a regime to provide sustainable governance. The IRR approach thus makes it possible to determine to what degree UWSE modernisation leads to a form of governance conducive to producing a sustainable path. Results of the analysis show that the modernisation of urban water systems in Europe does not lead to sufficient change in urban water management to achieve a sustainable process. This pessimistic assessment is based mainly on the observation of a lack of coherence in urban water systems in Europe.

To better understand how the study reaches this conclusion, the present paper is divided into three parts. The first part reviews the underlying principles and the development of the governance framework for the UWSE. The second part presents the analytical grid used in examining the IRR, while the third part assesses the sustainability prospects of European urban water systems.

I. THE COMMON CHARACTERISTICS OF UWSE MODERNISATION: TECHNICAL

STANDARDISATION AND LIBERAL GOVERNANCE

The impact of the European Union on urban water system management in Europe is becoming increasingly marked, particularly following the introduction of the subsidiarity principle. European regulation is becoming an increasingly significant factor in national water rights in EU countries and is thus one of the main components of UWSE management. This regulation was formally introduced on 6 May 1968 with the first European Water Charter and has undergone several phases in its development (Fig. 1). Thus, analysing the development of regulation enables us to characterise the modernisation process dealt with in this article. In our analysis of the different chronologies dealing with European regulation of water resources and associated activities [START_REF] Kallis | The EU Water Framework Directive: Measures and Implications[END_REF][START_REF] Kaika | The Water Framework Directive: A New Directive for a Changing Social, Political and Economic European Framework[END_REF], we refer in particular to the study by [START_REF] Allouche | Water Sector Evolution Scenarios: The Case of Europe[END_REF]. This chronology is based on the European research programme [START_REF] Euromarket | Analysis of the European Union's Explicit and Implicit Policies and Approaches in the Larger Water Sector[END_REF]Euromarket ( -2005) ) and brings it up to date. Furthermore, this approach to the subject differs little from that used in the other analyses cited. European regulation can be divided into three phases, or generations: [1973][1974][1975][1976][1977][1978][1979][1980][1981][1982][1983][1984][1985][1986][1987][1988]; [1988][1989][1990][1991][1992][1993][1994][1995]; [1995-present day]. The third phase represents the modernisation discussed in this article.

During the first regulation phase, the European Union introduced rules aimed at controlling the quality of the resource and limiting the impact on uses, mainly through drinking water standards and pollution thresholds. This type of regulation controls the immission of polluting substances1 , and is in line with two of the European political objectives of that time: harmonisation of environmental rules, with a view to facilitating trade in particular, and protection of public health [START_REF] Kallis | Evolution of EU Water Policy: a Critical Assessment and a Hopeful Perspective[END_REF]. The rules resulting from the second phase continued this effort and completed it by dealing directly with the sources of pollution and targeting specific sectors (urban water, etc.). Regulation took the form of a command and control system focussing then on the sources of emissions that degrade the resource. This pollution control was aimed at meeting environmental protection objectives and not simply with protecting uses. It should be noted that these two generations of regulations are anthropocentric, even though the second leaves a little more room for environmental concerns [START_REF] Euromarket | Analysis of the European Union's Explicit and Implicit Policies and Approaches in the Larger Water Sector[END_REF].

Finally, the third and current phase of regulation represents a paradigm shift with respect to the preceding periods. Rather than continuing to manage the resource and its uses in a selective and sector-based manner, the European Union began to promote integrated water resources management (IWRM). The objectives remain environmental but achieving them must remain compatible with the development of human activities. The implementation of means to achieve sustainable development is at the heart of this generation of regulations, and the European Water Framework Directive (WFD) spells out the fundamental principles. This chronology reveals a change in European regulations in both substance and form. European regulations on water developed firstly by taking into consideration specific problems as they arose (agriculture, quality, technology, urban water, etc.) and then proposing procedural rules. Following this, an effort was made to link the different problems so that a holistic approach to water management could gradually be put in place. Thus in 1991, Directive 462 drew up guidelines for pan-European water management which were followed by sectoral recommendations, such as in 1993 and 1994 with recommendations 1224 and 1232, dealing respectively with resource protection and water and agriculture. Again in 1991, the UWWTD imposed obligations regarding the collection and treatment of wastewater and acted directly on the management of UWSEs. In 2000, the WFD introduced new water management principles in Europe and became the main element in the third phase of the development of European regulations. Its novelty lay in the assumption of a positive correlation between methods of governance, in particular those recommended by new public management, and protection of the environment (Fig. 2). However, the directive evolved in function of the constraints observed during implementation and was amended in 2001, 2008 and 2009. Fig. 2: European principles of water management contained in WFD 1. "Water is not a commercial product like any other, but, rather, a heritage which must be protected and defended".

2. "Sustainable use of water", "take into account the vulnerability of aquatic ecosystems".

3. Good quality, strengthening of water protection standards: "good ecological status within a period of 15 years" (any exception must be justified).

4. Quantity: calculation of minimum discharge of rivers, for example, on basis of amount of water that can be abstracted while respecting the requirements of aquatic areas (abandonment of water requirements of different users, industry, agriculture, drinking water, etc). 5. "Polluter pays" principle.

6. "Water pays for water" principle.

7. Governance based on districts corresponding to river basins or catchment areas 8. … based on user participation on catchment area committees.

Source: Gilles Massardier, 2011: 12. In this article, we consider that the paradigm shift brought about by the third generation of regulations is providing impetus to the modernisation of urban water services in Europe. The study therefore focuses on this period and, among all the rules promulgated, gives paramount importance to the WFD2 . The WFD is in line with an anthropocentric approach to sustainable development; it protects the resource both qualitatively and quantitatively but without neglecting economic efficiency. This ambition to integrate the three pillars of sustainable development is reflected in the essential principles of the directive such as integrated management based on river basins, attainment of good ecological status, and incentives to set up public-private partnerships (PPP). In addition, the WFD also breaks with the old European standards concerning methods of regulation. As illustrated by the objective of attaining good ecological status for the resource, management results remain important, but now management procedures are also imposed and recommended, such as implementation of the "polluter pays" principle [START_REF] Moss | The Governance of Land Use in River Basins: Prospects for Overcoming Problems of Institutional Interplay with the EU Water Framework Directive[END_REF]. The modernisation of water management practices promotes a form of water governance that is no longer concerned only with protection of the resource and its uses.

In support of this observation, it may be noted that article 9.1 of the WFD states that "water-pricing policies provide adequate incentives for users to use water resources efficiently, and thereby contribute to the environmental objectives of this Directive". The WFD uses economic incentives and market mechanisms to organise management of the sector. Modernisation of the water sector is a continuation of the movement to liberalise all network infrastructures begun in the 1990s [START_REF] Finger | Water and Liberalisation: European Water Scenarios[END_REF]. The structure of the market makes it difficult to ensure atomicity among suppliers in a limited spatial area. Thus, in Europe the search for efficiency in the water sector resulted in an organisation based on the theory of contestable markets (Baumol, 1982) and de-integration of the sector (Demsetz, 1987). The contestability of markets should ensure an optimal allocation of resources while de-integration would produce new spaces in which competition can take place. Operators would become legal entities under private law, instead of and in the place of public monopolies.

UWSE modernisation is therefore based on a multiplication of technical standards ensuring preservation of the resource and protection of its uses as well as on a set of rules favouring the privatisation and liberalisation of the sector so as to improve the efficiency of governance. This modernisation may be seen as the combination of the pursuit of environmental objectives (protection and preservation) and rationalisation of the governance process (privatisation and liberalisation). The process gives impetus to two dynamics of urban water management in Europe: an increase in standardisation and a liberal approach. By reconciling these two dynamics, the European authorities hope to organise the sustainable management of urban water resources. We may therefore identify a common basis for a European model of water management, even though infra-European diversity may also be observed (between the German, French and English models). This diversity takes the form of variations of the European model and is reflected in the different institutional forms observed in the implementation of these shared principles [START_REF] Finger | Water and Liberalisation: European Water Scenarios[END_REF][START_REF] Ménard | Liberalization in the Water Sector: Three Leading Models[END_REF]. Two factors explain the polymorphism of the European water management model: the different legal backgrounds of the countries concerned and the variety of definitions/perceptions of a public service [START_REF] Lorrain | Urban Capitalisms: European Models in Competition[END_REF].

Having presented the main characteristics of the modernisation of UWSEs, noting their common aspects as well as their variations, we will now take a closer look at the IRR research programme.

II. IRR RESEARCH PROGRAMME: COMBINING PUBLIC POLICY ANALYSIS AND ECONOMIC INSTITUTIONALISM

To obtain a clear understanding of the analytical framework of IRRs before applying it to UWSE modernisation, it is important to first examine its foundations (II.1), and then its capacity to describe (II.2) and predict (II.3).

II.1 ANALYTICAL BASES: AN EMPIRICAL AND THEORETICAL CRITIQUE OF ENVIRONMENTAL POLICIES IN EUROPE

The IRR research programme is underpinned by an empirical and theoretical critique of European environmental policies (Knoepfel and Nahrath, 2005;[START_REF] Knoepfel | Régimes institutionnels de ressources naturelles: analyse comparée du sol, de l'eau et de la forêt[END_REF][START_REF] Gerber | Institutional Resource Regimes: Towards Sustainability through the Combination of Property-Rights Theory and Policy Analysis[END_REF]. The empirical evaluation is based on the study on environmental history by [START_REF] Mcneill | Something New Under the Sun: An Environmental History of the Twentieth-Century World[END_REF], which provides a diagnostic analysis of environmental degradation and the non-sustainable path of human development. Based on this historical analysis, the advocates of IRRs distinguish between different conceptions of environmental policies and point out the paradox that exists among them.

The first, so-called classical, conception is the least sustainable and "confines itself to reasoning in terms of limiting the emission of pollutants" [Transl] (Knoepfel and Nahrath, 2005: 207). The second conception attributes the objective of sustainable development to environmental policies: this involves reconciling the economic, ecological and social requirements relating to a resource. This type of policy represents progress in relation to the first approach, but it has proved to be not entirely satisfactory. "Sustainability policies" are focused on "the conditions for allocating the quantities of resources exploited" [Transl] with a view to meeting the requirements mentioned above (idem: 207). This logic presupposes a fairly abundant quantity of resources to ensure the production of goods and services demanded. In addition, as we have seen with the classical approach to policy, standards only restrict immissions and emissions of pollutants. Consequently, an "ecologically clean overexploitation of the resource" [Transl] may occur and the development path of different uses may become non-sustainable (ibidem: 208). Following criticism of the environmental policies resulting from these two conceptions, a third conception was proposed in order to genuinely coordinate uses in a sustainable manner. The authors maintain that the effectiveness of environmental policies hinges on the distinction between resource sustainability and resource use [START_REF] Gerber | Institutional Resource Regimes: Towards Sustainability through the Combination of Property-Rights Theory and Policy Analysis[END_REF]. We refer to this third conception by using the term "distinctive sustainable policies".

From a theoretical standpoint, a public policy approach comes up against one major limitation. It only considers the resource through sectoral analyses that are independent of each other, so that it is difficult to obtain an overall understanding of resource problems (Knoepfel and Nahrath, 2005;[START_REF] Knoepfel | Régimes institutionnels de ressources naturelles: analyse comparée du sol, de l'eau et de la forêt[END_REF][START_REF] Gerber | Institutional Resource Regimes: Towards Sustainability through the Combination of Property-Rights Theory and Policy Analysis[END_REF]. This limitation stems from the actual conception of public policies that tend to separate the issues identified. Institutional economics provides an analytical framework for identifying the links between different public policies, namely through notions of coordination and institutional arrangements. Based on the work of [START_REF] Bromley | Environment and Economy: Property Rights and Public Policy[END_REF]Bromley ( , 1992) ) and [START_REF] Ostrom | Governing the Commons: the Evolution of Institutions for Collective Actions[END_REF][START_REF] Ostrom | Property Rights Regimes and Common Goods: a Complex Link[END_REF], the IRR research programme postulates that there is compatibility between the analysis of public policies and institutional economics. Enhanced by the complementarity of the two approaches, the research programme goes beyond the theoretical limits outlined above.

These opening remarks help characterise the IRR approach. It is an approach combining public policy analysis and institutional economics that is specific to the study of natural resources management. More particularly, it questions the sustainability of the management practices used for a resource and related goods and services. Its axiomatic nature limits the field of study to those territories in which the formal rules are the principal source of regulation, in other words essentially the OECD countries. This focus on the written rule makes it possible to identify the main factors motivating and governing the choices of actors participating in UWSEs (Bolognesi, 2012). Furthermore, the work of the AFD, the French Development Agency, using data on national institutional profiles, confirms the relevance of restricting the analysis to the formal rules in OECD countries by showing the high degree of formalisation of regulation systems [START_REF] Meisel | A new Institutional Database: "Institutional Profiles2006[END_REF].

II.2 OBJECTIVE OF IRRS FROM THE PERSPECTIVE OF POSITIVE ECONOMICS: IDENTIFICATION OF WAYS OF REGULATING A NATURAL RESOURCE

An IRR is a means of governance of the uses of a given natural resource in a defined territory. In other words, it is the sum of public policies and property rights regulating the uses of a resource (Kissling-Näf and Kuks, 2004;Knoepfel and Nahrath, 2005;[START_REF] Gerber | Institutional Resource Regimes: Towards Sustainability through the Combination of Property-Rights Theory and Policy Analysis[END_REF]. In terms of positive economics, the objective of IRRs is to identify the governance mechanisms at work in regulating a natural resource. Consequently, it focuses on public policies and the structure of property rights. All these regulatory instruments are brought together in the two components of an IRR, respectively the policy design and the regulatory system for public policies and property rights. The weight of the two components in the regulation structure varies from one IRR to another, making it possible to distinguish between regimes that are organised essentially through the structure of property rights and those for which public policies are the main means of coordination.

Policy design comprises six elements and public policies give it concrete form (Knoepfel and Nahrath, 2005). The six elements are as follows:

1. Definition of problem and collective objectives; 2. Causality model3 ; 3. Public policy stakeholders: targets, beneficiaries and political and administrative actors; 4. Policy instruments; 5. Political and administrative arrangements; 6. Outputs.

Policy design results in the formulation of a public policy that will impact on the uses of the resource. In the context of IRRs, an understanding of public policies is obtained via a study of public law4 , considered to be the formal manifestation of public policies. Finally, policy design and public policies help define use rights for the resource. The second component of an IRR, the regulatory system, groups together formal property rights over the resource as well as the use and disposal rights which result from these5 . Private law6 , corresponding to the French civil code, is a formal manifestation of the rights of the regulatory system. Thus, property rights come from the regulatory system while usage rights are jointly defined by the regulatory system and policy design (in general, public policies limit or refine the usage rights allocated.

The possibilities for combining these two components are numerous and four different ways of regulating resources can be identified (Knoepfel and Nahrath, 2005;[START_REF] Gerber | Institutional Resource Regimes: Towards Sustainability through the Combination of Property-Rights Theory and Policy Analysis[END_REF], based on the impact of the policy design and the regulatory system on property and usage rights. Type 1 regulation has no impact on the system of rights and essentially involves the creation of incentive mechanisms. Type 2 has a limited impact on the structure of rights through the use of ex post specifications or restrictions on the allocation of rights. Type 3 modifies the breadth and content of rights through a redefinition of the institution of formal property, for example, via an amendment to the civil code. Finally, type 4 procedures redefine the allocation structure of property titles, for example through privatisation.

II.3 OBJECTIVE IN TERMS OF NORMATIVE ECONOMICS: DEFINITION OF AN INTEGRATED IRR FOR SUSTAINABLE GOVERNANCE

The normative objective of IRRs is to formulate recommendations to improve the sustainability of resource regulation systems. The procedures for attaining this objective are logically structured around three analytical steps: identification of the scope of an IRR, its classification, and the formulation of hypotheses linking the characteristics of an IRR to its sustainability potential. The notions of "extent" and "coherence" define the scope of an IRR. The extent refers to the number of goods and services regulated by an IRR at any given time. To evaluate it, these goods and services have been listed for different natural resources, including water [START_REF] Knoepfel | Régimes institutionnels de ressources naturelles: analyse comparée du sol, de l'eau et de la forêt[END_REF]. The ratio between the extent observed and all the goods and services used gives the relative extent of the IRR. When the ratio is less than 1, it indicates the possibility of non-regulated rivalries, while a ratio of above 1 suggests over-regulation. The coherence of an IRR relates to the content of the different sources of regulation of an IRR and the coordination between them [START_REF] Gerber | Institutional Resource Regimes: Towards Sustainability through the Combination of Property-Rights Theory and Policy Analysis[END_REF]. Three forms of coherence may be distinguished. Coherence within the policy design ensures compatibility between its six elements, on the one hand, and between the different public policies on the other. Coherence within the regulatory system means that property rights are clearly defined and non-contradictory. Finally, external coherence reflects a satisfactory link between the two components of the IRR, for example correspondence between target groups and holders of rights under the regulatory system.

Based on the extent and coherence characteristics of an IRR, a typology can be proposed distinguishing four possible IRR forms: non-existent, simple, complex and integrated (Kissling-Näf and Kuks, 2004; Knoepfel and Nahrath, 2005;[START_REF] Knoepfel | Régimes institutionnels de ressources naturelles: analyse comparée du sol, de l'eau et de la forêt[END_REF][START_REF] Gerber | Institutional Resource Regimes: Towards Sustainability through the Combination of Property-Rights Theory and Policy Analysis[END_REF] (Fig. 3). A non-existent RIR indicates the absence of any form of usage regulation for the resource. A simple IRR reflects emerging regulation for a resource, where only a limited number of goods and services (among those actually used) have so far been regulated, but in a coherent manner (the sources of incoherence being reduced). An IRR becomes complex when most of the goods and services used are regulated but in a way that is not very coherent. Finally, an integrated IRR indicates the coherent regulation of all the goods and services used. Empirical evidence shows this form occurs mainly when regulation is public or is administered by a powerful stakeholder representing collective interests (Knoepfel and Nahrath, 2005). Each IRR studied is classified according to this typology. one hand, and the sustainability potential, on the other 7 . The first conjecture suggests that the move towards an integrated form increases the potential for sustainability and leads to two sub-conjectures, each specific to the extent and coherence of the IRR. The second conjecture relates to the evolution of an IRR. It establishes a positive causality between the level of threat to a resource, its perception as an issue of collective action and, consequently, the expansion and greater coherence of the IRR. This interplay of conjectures completes the normative objective of the research programme of the IRRs, by which the sustainable use of a resource is attained through an increase in the extent and coherence of regulation. The approach thus makes sustainability a central objective in the governance of a natural resource and supports the need to build an integrated IRR.

Having presented the subject of analysis and the theoretical elements, we will now reintegrate empiricism in the analytical framework with the aim of gaining insights into the prospects for sustainability of UWSEs following their modernisation.

III. THE LIMITED SUSTAINABILITY POTENTIAL OF UWSES: COMPLEX IRRS

Identification of the scope of UWSEs helps evaluate their potential for sustainability. Extent appears large (III.1) while coherence seems to be insufficient (III.2).

III.1 MODERNISATION AS A STEP TOWARDS SUSTAINABILITY: A FACTOR IN THE EXPANSION OF UWSES

By interpreting UWSE modernisation by means of the analytical framework presented earlier we conclude firstly that the extent of the UWSE is large and, secondly, that two different processes are at the origin of this large coverage (Fig. 4). The first process relates to the classic development of technical standardisation, which we refer to as expansion through regulatory measures. The second process concerns the change in the form of urban water supply services, which we qualify as processual. We will now discuss this expansion in terms of both its form and dynamic.

Technical standardisation of water uses meant that the extent of UWSEs was increased as a result of the introduction of regulatory measures. This dynamic process stems from the multiplication of standards on processes, emissions and immissions, produced essentially by the public authorities with a view to regulating water uses and their impacts [START_REF] Barraqué | Past and Future Sustainability of Water Policy in Europe[END_REF]. By looking at the timeline of European regulations we can see the direction taken by the regulatory process and the change in the actual purpose of control measures. Originally, technical standards served as health objectives and, generally speaking, restricted the immission of polluting substances into the resource. Following this, an environmental objective to protect the actual resource, with corresponding emission standards, was introduced, leading to a further increase in extent. At the same time, the identification of particularly sensitive areas encouraged the creation of technical standards specific to targeted sectors, as illustrated in the tables of the UWWTD in the Appendix. Finally, during modernisation, the attempt to harmonise practices, etc., resulted in the emergence of 7 In our opinion, and based on the epistemology of [START_REF] Lakatos | The Methodology of Scientific Research Programmes[END_REF], these conjectures constitute both a cornerstone and a stumbling block of the research programme, a cornerstone because they establish the originality and the major contribution of the corpus, and a stumbling block because, given that the conjectures are not demonstrated, the normative and predictive objective of the IRRs appears unstable. However, experience has neither refuted the conclusions nor falsified the research programme. This therefore enables us to use IRRs with caution. The apparent shortcomings of the research programme are a reflection of its relatively recent beginnings and indicate that it is still maturing, while the development of its positive heuristic constitutes a major element in its future progression.

procedural standards governing actual uses (obligation of water treatment techniques, for example) and no longer simply objectives in terms of results. In addition, the reason for control measures has also evolved. Increased market power and the presence of private actors in the supply of urban water services forced public authorities, in a more systematic manner, to supervise activity by means of standards in order to remedy any possible negative externalities and to maintain general interest in the resource.

The second dynamic whereby UWSE regulation is increased, which we call processual expansion, is a direct consequence of the application of the principles of governance incorporated in the modernisation process. Thus, modernisation gives impetus to changes in UWSE regulation methods, two of which appear essential. First, the encouragement given to PPPs, and to privatisation in general, led to a redefinition of the allocation structure of property rights (type 4 regulation), the privatisation of English RWAs in 1989 being the most symptomatic example. Second, generalisation of the use of economic instruments with a view to "rationalisation" of management increased the importance of type 1 regulation in UWSE governance. The modification in substance or form of these two types of regulation encouraged the liberal orientation of modernisation, as underlined in the first part. It attributes increasing importance to the market, but coordination through the market implies recourse to formal regulation.

Market trading requires firstly the existence and/or definition of property rights and then takes place by means of contracts drawn up between the stakeholders. Thus we maintain that liberal regulation and market supply of urban water services in essence increases the goods and services formally regulated in UWSEs. In this sense, modernisation of UWSE governance increases the extent of the IRR by its very nature. In particular, it results in a high relative extent since all the good and services used will be formally regulated by the market. Knowing that the extent of urban water systems in Europe is high makes it possible to better characterise them using the IRR typology and to provide an interim opinion on their sustainability potential. First, among the four forms of IRR, only the complex and integrated types have a high extent. UWSEs therefore belong to one of these two categories and the forthcoming analysis of their coherence will enable us to determine which one. Second, by virtue of conjecture 1.1 linking extent and sustainability, we may assume that modernisation exerts a beneficial effect on the sustainability of a UWSE by increasing its extent and ensuring a high degree of relative extent. Thus far, the coherence dimension is decisive in determining the overall sustainability potential that modernisation confers on the UWSE.

III.2 PERSISTENCE OF INCONSISTENCIES IN REGULATION AS A LIMIT TO INTEGRATION

OF THE IRR Analysis of IRR coherence involves studying the coherence of both policy design and the regulatory system, as well as their cross-coherence. To carry out this analysis, we sought to identify inconsistencies and malfunctions. Ultimately, the results confirm the conjecture that inconsistencies subsist despite the acknowledged modern-day attempts to put an end to these limits to sustainability by harmonising European water management principles.

The regulatory system appears to be the most coherent component of UWSEs, which can be largely explained by the choice of study area. As pointed out in the opening remarks of the second part, European territories are particularly suited to an analysis in terms of IRR thanks to the mostly formal regulation systems. This long tradition of coordination around property rights has made it possible to put in place a set of institutions and organisations capable of ensuring the coherencein the IRR senseof the regulatory system. The development goes with the development of the rule of law and the public bureaucracy (Brousseau, Schemeil and Sgard, 2010: 254). Nevertheless, it should be stressed that internal coherence of the regulatory system is not necessarily equivalent to stable and clear management at the time of interaction between stakeholders. Indeed, the multiplication of stakeholders also generates uncertainty in strategic areas and the possibility of conflict, but thanks to internal coherence such problems can be settled subsequently. The analyses of [START_REF] Bakker | Privatising Water, Producing Scarcity: The Yorkshire Drought of 1995[END_REF]2010) on the privatisation of the English sector illustrate this remark, as does, in a more concrete fashion, the management of the 1995 drought in England8 .

The policy design of UWSE modernisation suffers from more internal inconsistencies than the regulatory system. The two main indicators are the debate on how to attain good ecological status and, more generally, how to ensure conformity of local management systems with European directives. The objective of achieving good ecological status of water by 2015, in which urban uses will play a major role, appears difficult to reach 9 . In addition, scientists are voicing reservations on the methods of measuring efforts and the results achieved with respect to their rigour, diversity and comparability, with the classification of certain water bodies being re-examined [START_REF] Hering | The European Water Framework Directive at the Age of 10: A Critical Review of the Achievements with Recommendations for the Future[END_REF][START_REF] Beniston | Obstacles to Data Access for Research Related to Climate and Water: Implications for Science and EU Policy-making[END_REF]. It is also true to say that ensuring conformity with management methods recommended by the WFD is not always an easy matter [START_REF] Wright | Operationalising Active Involvement in the EU Water Framework Directive: Why, When and How?[END_REF], as we saw for example with German reticence towards privatisation. Thus, coordination between the different levels of UWSE governance is characterised by malfunctions that reduce the coherence of the policy design for modernisation. Nevertheless, mention should be made of the European readjustments: the WFD has been amended three times, going so far as to bring more flexibility to external funding possibilities in the water sector.

The main sources of inconsistency in UWSEs lie at the interface of policy design and the regulatory system10 . All the differences between the States and the European Commission testify to these external inconsistencies. Representing about 20 % of disputes, water is one of those areas that are most in breach of European environment legislation [START_REF] Keller | Application du droit communautaire de l'environnement[END_REF]. The United Kingdom (56) and Germany (57) are guilty of fewer infractions than France (74), while Belgium has the worst record with no less than 109 infractions reported in December 2010. To have an idea of the risks incurred, the penalties relating to French case C-280/02 concerning urban waste water were estimated at several hundred million euros [START_REF] Keller | Pilotage de la politique de l'eau[END_REF].

The degree of coherence of UWSEs is not high, mainly because of the difficulty of organising a harmonious and multi-level policy. This lack of coherence appears in particular externally, a fact also noted by stakeholders. Members are therefore making a concerted effort to increase coordination among the different elements of UWSE regulation. By knowing the scope of a UWSE, we are able to deduce the type of IRR that it belongs to and the potential for sustainability that modernisation would provide.

III.3 EXPANSION VERSUS COHERENCE: THE PARADOX OF MODERNISATION

On the basis of the characteristics defining the scope of UWSEs, i.e. large extent and poor coherence, we are able to deduce the type of IRR to which they belong. The large extent eliminates the possibility of "non-existent" or "simple" types of IRR and the low level of coherence makes an "integrated" IRR unlikely. Consequently, the modernisation of water management in Europe is helping to shape UWSEs as "complex" IRRs (Fig. 5). The hypotheses relating to IRR sustainability suggest that complex IRRs are regulated by a governance system that does not maximise sustainability potential. Thus, as things stand, modernisation would not ensure that UWSEs develop with maximum sustainability potential. This conclusion rests on the ambivalence of modernisation. We should therefore emphasize the effects, both positive and negative, of expansion through regulatory measures and processual expansion on the sustainability of UWSEs. Expansion through regulatory measures increases the total amount of regulated goods and services, which directly improves the sustainability potential of the systems. However, it reduces this potential by making the system more complex. This regulation through standards increases the technical complexity of supplying the services, which results in a reduction in system coherence. Operators find it difficult to integrate such regulation into their systems. In addition to this technical aspect, ensuring conformity entails a financial cost that may threaten the internal coherence of the policy design and the external coherence of UWSEs11 . Faced with these additional costs relating to technical standardisation, the supervision and rationalisation of governance processes stemming from procedural regulations reduce the sources of financing. The principles of full cost recovery and "water pays for water" are examples of this problem [START_REF] Barraqué | Past and Future Sustainability of Water Policy in Europe[END_REF]. Thus, while costs increase, financing possibilities decrease, and the question of investment in infrastructure becomes a major problem in UWSE management. There is therefore an area of friction between the technical component and the economic/institutional component of expansion through regulatory measures. This friction causes regulatory incoherence and eventually diminishes the sustainability potential of UWSEs. Moreover, expansion through regulatory measures reinforces the tension between the socio-environmental and economic objectives required to achieve a sustainable management system for urban water services in Europe.

Processual expansion has a similar effect on the sustainability of UWSEs. By recourse to property rights and contracts, it increases the extent of the system, ensures a relative extent that is at least equal to 1, and improves sustainability potential. This recourse, however, decreases UWSE coherence because of the characteristics of coordination through the market, and reduces sustainability potential. Thus, institutional economics considers that property rights and contracts are incomplete [START_REF] Barzel | Measurement Cost and the Organization of Markets[END_REF][START_REF] Brousseau | How to Design Institutional Framework for Markets: New Institutional Economics Meet Needs of Industrial Organization[END_REF]. This incompleteness implies an inability to take into account all the possible developments and changes in transactions and does not totally eliminate uncertainty. Coordination through the market does not eradicate ex ante uncertainty, so that contracts require readjustments and safeguard mechanisms must accompany contracts and property rights. This uncertainty leads to difficulties in organising the different elements of regulation and is a hindrance to the achievement of IRR coherence.

It appears that the positive impact of expansion processes is counterbalanced by the appearance of inconsistencies that weaken the sustainability potential of UWSEs. In this respect, modernisation has a paradoxical effect on the sustainability potential of UWSEs. On the one hand, modernisation increases the extent of UWSEs by means of regulatory and processual expansion, while on the other hand the way in which these two mechanisms function generates inconsistencies and prevents complete integration of UWSEs. It therefore appears, at first sight, that modernisation develops the sustainability potential of water management in European cities by producing rules that add substance to system regulation. However, a more detailed look reveals that the costs of coordination associated with these rules do not seem to be taken into account in modernisation in its current form. This paradox limits the sustainability potential of management systems for urban water services in Europe.

CONCLUSION

The modernisation of UWSEs is characterised by an increase in technical standardisation and a liberal trend in governance. This article evaluates the capacity of this modernisation process to direct the UWSE along a sustainable development path. With this aim in mind, we used the analytical framework of the IRRs to assess the sustainability potential of UWSEs according to their extent and their coherence. The analysis reaches two main conclusions, the first positive, the second negative.

First, UWSEs figure among the complex IRRs. We show that modernisation allows expansion through regulatory measures and processual expansion of UWSEs, which means that the "extent" dimension is high. However, UWSE modernisation is subject to malfunctions and does not manage to ensure a sufficient level of coherence to reach the status of an integrated IRR. We identify the main sources of this low level of coherence as being related to the coordination between policy design and the regulatory system, the prime cause of which is the difficulty of setting up a multi-level governance system. Second, modernisation will not provide UWSEs with a guarantee of sustainable development. The complex status of UWSEs means that, according to the conjectures relating to IRRs, sustainability potential is limited. Admittedly, since the extent dimension is high, there is less chance of any unsettled conflicts over use, but the lack of coherence reduces the effectiveness of regulation resulting from implementation of public policies and of the property rights system.

Ultimately, the Europeanization of this public service does not seem to be an adequate solution to the problems of sustainability facing urban water systems in Europe. Moreover, it raises the more general question regarding the capacity of a governance system with a liberal

Fig. 3 :

 3 Fig.3: Typology of IRRs according to their extent and coherence

Fig. 4 :

 4 Fig. 4: The two dynamics of expansion contained in the modernisation of UWSE Expansion through regulatory measures

Fig

  Fig.5: Classifying UWSE as complex IRR Low coherence High coherence High extent Complex IRR

  Fig. 1: Main laws and regulations concerning water standards enacted at European level

	Text		Year Objective
			Generation 1
	European	Water	1968 1 st European instrument dealing with water
	Charter
	Directive		1975 Surface water
	75/440/EEC
	Directive		1976 Dangerous substances
	76/464/EEC
	Directive 80/68/EEC 1980 Groundwater
	Directive		1980 Quality of water intended for human consumption (revised by 98/83/EC)
	80/778/EEC
			Generation 2
	Directive		1991 Urban waste water
	91/271/EEC
	Directive		1991 Guidelines for a pan-European water resources management policy (supply and
	91/462/EEC		quality)
	Directive		1991 Nitrates from agricultural sources
	91/676/EEC
	Recommendation	1993 Protection and management of fresh water resources (this originated in the
	1224		Freshwater Europe action programme)
	Recommendation	1994 Water resources and agriculture
	1232
			Generation 3
	Directive 96/61/EC	1996 Integrated pollution prevention and control
	Directive 98/38/EC	1998 Quality of water intended for human consumption
	Resolution 1222	2000 Water resources and agriculture
	Recommendation	2000 Link between science and technology to balance supply and demand, especially
	1471		in the Mediterranean basin.
	Directive		2000 Water Framework Directive (amended by decision 2455/2001/EC and directives
	2000/60/EC		2008/32/EC; 2008/105/EC; 2009/31/EC)
	European	Water	2001 European water resources charter (replacing charter of 1968)
	Charter
	Directive		2004 Public procurement in the water, energy, transport and postal services sectors
	2004/17/EC
	Directive 2006/7/EC	2006 Quality of bathing water
	Directive		2006 Pollution caused by certain dangerous substances
	2006/11/EC
	Directive		2006 Protection of groundwater
	2006/118/EC
	Directive		2008 Environmental quality standards
	2008/105/EC
	Directive		2010 Industrial emissions: Integrated pollution prevention and control
	2010/75/EU

"Immission" refers to the concentration of pollutants in the water, while "emission" refers to the action of diffusing pollutants in the water. In the first case, emphasis is on the host environment of pollutants; in the second, it is their source.

All normative and preparatory acts, and those relating to water management and protection in Europe, can be accessed via http://eur-lex.europa.eu/fr/dossier/dossier_61.htm#1, consulted on 10-09-2012.

A model of causality identifies the actors responsible for the problem of collective action and the mechanisms capable of modifying their behaviour in the manner recommended by element 1. The model also takes into account element 3 (stakeholders) and

(instruments) of the policy design.4 The authors are aware that the distinction between private and public law appears clear in traditional Roman law but less so in common law legal systems(Knoepfel and Nahrath, 2005; Varone et al., 2008;[START_REF] Gerber | Institutional Resource Regimes: Towards Sustainability through the Combination of Property-Rights Theory and Policy Analysis[END_REF].In legal systems based on Roman law, public law governs interactions between private actors and the State.

Roman law distinguishes between right of disposal and right of use(usus, abusus, fructus). The right of disposal, (right to sell -abusus) applies to the transfer of the resource, while usus refers to the right of use and the prerogatives relating to the modification of the resource contained in the abusus.

In legal systems based on Roman law, private law governs interactions between private actors.

This drought revealed that the system of price-capping had not encouraged operators to invest sufficiently in infrastructure development so as to maintain the balance between supply and demand[START_REF] Bakker | Privatising Water, Producing Scarcity: The Yorkshire Drought of 1995[END_REF]. Later, the regulatory authorities and the State sent out new price signals to remedy this shortcoming.

This is also because these inconsistencies are the most visible and identifiable.

This cost is not negligible since it represents the majority of the increase in costs for suppliers. It comes mainly from the introduction of sanitation standards and the increasing complexity of drinking water treatment procedures in order to comply with regulations.

All the reports of member countries of the European Commission are available at: http://www.eea.europa.eu/themes/water/reporting-obligations, consulted on 27-09-2012. For France, in particular, the reader may consult: http://www.rapportage.eaufrance.fr/; for England: http://www.environmentagency.gov.uk/research/library/data/97343.aspx; for Germany, the report is available at: http://www.umweltdaten.de/publikationen/fpdf-l/3771.pdf.


Néstor Novoa

Thierry Roisnel

Vincent Dorcet

Jean-René Hamon
email: jean-rene.hamon@univ-rennes1.fr

David Carillo

Françoise Carolina Manzur
email: cmanzur@ucv.cl

Robin-Le Guen

Nolwenn Cabon
email: nolwenn.cabon@univ-rennes1.fr

David Carrillo

Françoise Robin-Le Guen

Anisyl and Ferrocenyl Adducts of Methylenepyran-Containing β-Diketone: Synthesis, Spectral, Structural, and Redox Properties

Keywords: Iron, β-diketone, methylenepyran, structure determination, ferrocene

come

Introduction

Acetylacetone, also known as pentane-2,4-dione or Hacac, the quintessential example of the 1,3-dicarbonyl class of compounds [RC(O)CHR"C(O)R""], was first prepared by Claisen about 125 years ago, from the base-catalysed condensation reaction between acetone and ethyl acetate [1]. Since that time, a number of alternative and more efficient synthetic pathways [2][3][4][5], including palladium-catalysed carbonylative -arylation of acetone [6], have been developed to produce a broad range of β-1,3-dicarbonyl containing organic substrates, as well as their metallocene-containing β-diketone counterparts of the type Mc-C(O)CH 2 C(O)R (Mc = ( 5 -C 5 H 5 )M( 5 -C 5 H 4 ), M = Fe (Fc), Ru (Rc) ; R = Me, CF 3 , Ph, Fc, Rc). Indeed, ferrocene-containing β-diketones were introduced in the late 1950s [7,8], shortly after the discovery of ferrocene [9], while its ruthenocene relatives were published only fifty years later [10]. This constant interest, over the years, of organic, inorganic and physical chemists to β-diketones and related compounds results from their valuable intrinsic chemical and physical properties. In particular, their keto-enol tautomerism has been extensively studied in solution by FT-IR and NMR spectroscopy and by electrochemistry and in the solid-state by X-ray single crystal diffraction analysis [11]. In solution, the 1,3-diketone cores generally exist as equilibrium mixtures of diketo [RC(O)CHR"C(O)R""] and enolone [RC(O)CR"=C(OH)R""] tautomers [10][11][12][13][14][15][16][17][18], whereas in the solid-state, the keto-enol isomer is generally the sole form observed [14][15][16][17][18][19]. This feature has been rationalized in terms of resonance-assisted hydrogen bond (RAHB) model based on intercorrelation between spectroscopic and crystal structure parameters, originally introduced by Gilli and co-workers [18], for explaining the abnormally strong internal hydrogen bonding within the enolone fragment. It has long been documented that β-diketones are important building blocks in organic synthesis [20][21][22], where in addition to their established role in the synthesis of various N-containing heterocyclic derivatives [23,24], they have been widely used for the construction of polydentate Schiff base ligands [25]. Likewise, β-diketone ligands are versatile metal coordinating agents and have played a significant role in coordination chemistry for a long time [26]. Due to the presence of two oxygen donor atoms and, as stated above, facile keto-enol tautomerism, they easily coordinate with metal ions after deprotonating the enolic hydrogen atom and provide stable metal complexes with six-membered chelate rings. Indeed, the widely used uninegative [O-CR-O] - chelating group is capable of stabilizing mono-and polynuclear complexes of d-[27] and fblock [28] metal ions with, for instance, applications in catalysis [29], and functional materials [30], and has recently gained increasing attention as constituents of polydentate ligands in metallo-supramolecular chemistry [31].

Even though less largely utilized, chalcogenomethylenepyran cores are encountered as building components in various domains including one dimensional organic conductors [32],

medicinal technology [33], liquid crystals [34], nonlinear optics (NLO) [35], and molecular machine [36]. Despite the great potential of this class of molecules, organometallic chalcogenomethylenepyran compounds remain scarce. Caro and co-workers first developed and used benchrotrenyl pyrylium salts as amino acid and protein labelling reagents [37].

Those authors also opened simple and efficient routes to NLO active, unsaturated chalcogenomethylenepyran Fischer-type chromium and tungsten carbene complexes, as well as mixed sandwich iron hydrazones using pyrylium salts [38], or aldehyde functionalized methylenechalcogenopyrans [39]. Actually, -methylenepyrans, which are proaromatic donor, are attracting synthons as electron-donor parts in push-pull structures as they gain aromaticity upon internal charge transfer process.

In pursuit of this work, some of us were involved in the preparation of the first ferrocenylmethylenepyran derivative and have shown that its electro-or chemical oxidative coupling leads to the reversible formation of ethanediferrocenylbispyrylium salt through the dimerization of a ferrocenylmethylenepyran radical intermediate. Reversible deprotonation of ethanediferrocenylbispyrylium salt afforded an extended diferrocenylbismethylenepyran that was subsequently reversibly oxidized to ethenediferrocenylbispyrylium salt [START_REF] Ruiz | however, ferrocene is far from perfect as an internal reference[END_REF]. On the other hand, part of us have been interested for several years in the synthesis of functionalized ferrocenyl-containing diketones [17,41], as starting materials for the construction of push-pull unsymmetrical Schiff base complexes exhibiting NLO properties [42]. Thus, we thought that it would be of interest to design extended electron-rich ferrocenyl-containing chalcogenomethylenepyrans having a chelating coordination site, that could, upon electron and proton transfer sequences, become potential constituents of conjugated polydentate ligands.

In this piece of work, we report on the synthesis, the full analytical and spectroscopic characterization, and the electrochemical properties of a series of organic and organometallic complexes containing the methylenepyran framework bearing phenyl substituent at the 2,6 positions of the pyranyl ring, including three new β-diketones derivatives, namely, 1-{4-[ (2,6diphenyl-4H-pyran-4-ylidene) (2,6-diphenyl-4H-pyran-4-ylidene)methyl]phenyl}-3-(ferrocenyl)-propane-1,3-dione (4), and 1-(1,3-dioxobutyl)-1"-[ (2,6-diphenyl-4H-pyran-4-ylidene)methyl]ferrocene (7) (see formulae in Scheme 1). In addition, the crystal and molecular structures of the ferrocenylcontaining β-diketone 4, its organic precursor 2, and of the 1-acetyl-1"-[ (2,methyl] ferrocene derivative 6 were determined by X-ray single crystal diffraction analysis.

methyl]phenyl}-3-(4-methoxyphenyl)-propane-1,3-dione (3), 1- {4-[

Results and Discussion

Syntheses and spectroscopic characterization

Precursor 2 is readily obtained following a Wittig-type reaction of the easily accessible 2,6diphenyl-4H-pyran-4-yl triphenylphosphonium tetrafluoroborate salt 1 [43] with methyl 4formylbenzoate. Treatment of a THF solution of the heterocyclic phosphorane, generated in situ by reaction of the phosphonium salt 1 with n-butyllithium, with methyl 4-formylbenzoate for 4 hours at -75 °C, afforded the 4-methylbenzoate methylenepyran 2 in 75% yield after chromatographic purification and recrystallization from dichloromethanen-hexane mixture (Scheme 1). This reaction is, indeed, similar to that leading to the formation of the known ferrocenylmethylenepyran 5 [START_REF] Ruiz | however, ferrocene is far from perfect as an internal reference[END_REF]. Compound 2 is an air and thermally stable yellow crystalline solid with good solubility in THF, diethyl ether, dichloromethane and chloroform.

The organic and organometallic methylenepyran-containing -diketones were prepared from the well-known base-catalyzed Claisen condensation reaction [1], at ambient temperature using potassium tert-butoxide as basic initiator Moreover, in order to design extended electron-rich ferrocenylmethylenepyran having a chelating 1,3-dicarbonyl coordination site, it was necessary to prepare the corresponding acetyl precursor. Ferrocene is well-known to behave as an aromatic molecule. For example, it can be easily acetylated with acetyl chloride in the presence of AlCl 3 [44]. Therefore, ferrocenylmethylenepyran 5 was subjected to such a Friedel-Crafts acylation reaction in dichloromethane at 0°C for 2h (Scheme 1), yielding the corresponding acetylated derivative, 1-acetyl-1"-methylenepyranyl-ferrocene 6, that was isolated in 61% yield as a red microcrystalline powder.

Scheme 1 Synthesis of the new compounds ( 2)-( 4), ( 6) and (7). Under the experimental conditions described above for preparing 3 and 4, the condensation reaction between the electron-rich acetyl complex 6 and acetyl acetate failed. The increased electron-donating properties of the ferrocenylmethylenepyran fragment, with respect to the ferrocenyl one, lowers the acidity of the methyl hydrogen atoms of acetyl substituent which in turn necessitates the use of a stronger base. We, therefore, used lithium diisopropylamide as the active base initiator, a route that has proven effective in the synthesis of the targeted ferrocenylmethylenepyran-containing -diketone 7 (Scheme 1), although 7 was isolated in a modest 20% yield as an orange powder. Indeed, 1 H NMR analysis of the crude product showed that the -diketone was formed in 30% spectroscopic yield, with 23% of acetyl precursor 6, and 47% of unidentified product that could arise from self condensation of the acetyl starting material [14]. Complex 7 was separated from the reaction mixture by column chromatography. Use of N,N-dimethylacetamide instead of ethylacetate did not permit to improve the yield of 7.

The new compounds, isolated as microcrystalline powders, are thermally stable air and moisture insensitive on storage under ordinary conditions, exhibiting good solubility in common polar organic solvents but are less soluble in petroleum ether and n-hexane and can be crystallized from them. Their composition and identity are supported by elemental analysis, FT-IR, one-and two-dimensional NMR spectral data and mass spectrometry.

Additionally, the crystal and molecular structures of compounds 2, 4 and 6 were determined by single crystal X-ray diffraction analysis (see below).

The solid-state FT-IR spectra of all the new compounds exhibited medium band in the 1650-1400 cm -1 region assigned to the (C=C) stretching mode of the methylenepyran moiety. In addition, in the spectra of 2 and 6, the ester and acetyl functionalities are identified by their intense (C=O) stretching bands at 1715 and 1657 cm -1 , respectively. The solid state FT-IR spectra of the β-diketone derivatives 3, 4 and 7 are quite similar and showed C=O and C=C medium stretching bands at 1658-1598, 1656-1578 and 1655-1585 cm -1 , respectively, in agreement with keto-enol tautomeric forms [11]. The presence of the enolone isomer is also indicated by a broad band at 3414, 3446 and 3440 cm -1 , respectively, attributed to the asymmetric stretching mode of the O-H group involved in the [O-H•••O] intramolecular hydrogen bond. Moreover, the spectrum of 7 presents an absorption band at 1729 cm -1 that can be assigned to the (C=O) stretching vibration of the keto tautomeric form.

The formation of the new compounds 2-4, 6 and 7 were readily noticed in their respective 1 H NMR spectrum with in each case a sharp singlet at  3.87, 3.91, 2.36, 1.93 and 2.28 ppm assigned to the methyl ester protons of 2, the methoxy protons of 3, and the acetyl protons of 6, 7-enol and 7-keto, respectively. For 4, the sharp peak assigned to the protons of the free cyclopentadienyl ring was found at  4.23 ppm. Additionaly, for 6 and 7, one can note that the two types of hydrogen atoms of the substituted cyclopentadienyl rings containing either the electron withdrawing acetyl or "acac" group are deshielded (0.26 and 0.33 ppm for 6, 0.20 and 0.33 ppm for 7-enol, 0.22 and 0.30 ppm for 7-keto) compared to those attached to the cyclopentadienyl ring bearing the electron donating methylenepyran fragment.

Moreover, the 1 H NMR spectra of β-diketones 3 and 4, recorded at 25 °C in CDCl 3 , exhibited for the 1,3-dione fragment only one set of two singlets at  6.81 and 6.41 ppm for the vinylic C-H proton, and at  17.09 and 16.82 ppm for the O-H protons of the enol form, respectively. These downfield positions are in full agreement with the above discussed FT-IR data and also supported by the crystal structure of complex 4. The above mentioned solution behaviour, where no keto tautomer can be detected, is similar to that we recently reported for Cp-Fe (η 5 -C 5 H 4 )-C(O)CH=C(OH)(p-C 6 H 4 -O-C 5 H 9 O) [17]. By contrast, the 1 H NMR spectrum of the β-diketone 7, also recorded at 25 °C in CDCl 3 , showed an enol/keto signal pair, indicating that ( 7) does exist as a mixture of keto-enol and -diketone tautomers in a 73:27 spectroscopic ratio. The vinylic C-H singlet at  5.65 ppm (1 H) for the keto-enol form gave rise to a sharp resonance at  3.81 ppm (2 H) for the -diketone isomer. The downfield shifted O-H enol proton was observed at  15.98 ppm. In the three cases, enolization takes place exclusively away from the anisyl or ferrocenyl group. This is in agreement with previous observations [13][14][15][16][17][18], and with the existence of a resonance driving force instead of an electronic driving force to explain the dominance of the Cp-Fe(η 5 -C 5 H 4 )-C(O)CH=C(OH)CH 3 form toward the Cp-Fe(η 5 -C 5 H 4 )-C(OH)=CHC(O)CH 3 form [14]. Indeed, a linear relationship has been established between group electronegativity χ R on the Gordy scale and carbonyl stretching frequency υ(CO) of methyl esters [14,45]. In the case of complex 2, utilizing the carbonyl stretching frequency, one can evaluate the electronegativity of the phenyl methylenepyran (R) fragment to be around 2.0. By extrapolation, since the electronegativity χ R of the ferrocenyl group is lower than that of the phenyl group on the Gordy scale, one can evaluate the ferrocenylmethylenepyran fragment to have a lower χ R value than the phenylmethylenepyran fragment. Consequently, from an electronic point of view and assuming the value of 2.3 for the methyl group [14,45], the dominant enol isomer should be R-C(OH)=CHC(O)CH 3 . Similarly to the ferrocenyl -diketone [14], a resonance driving force may be taken into account to explain the observed dominant enol form for 7.

Interestingly, on passing from 7-enol to 4 and from 4 to 3, one can note two successive significant downfield shifts of 0.76/0.40 and 0.84/0.27 ppm for the vinylic and the enol protons, respectively, as a consequence of the participation of the pseudo-aromatic enol ring in the conjugated system, an effect that can be correlated with the increasing pyrylium character of the methylenepyran unit (see below).

The 1 H NMR spectra of compounds 2-4, 6 and 7 displayed also the three characteristic signal pattern attributed to the H-3, H-5 and H-7 methine protons of the methylenepyran fragment (see Table 1 and Fig. 1 for atom labelling scheme). The 1 H NMR chemical shifts of the H-3/H-5 proton have been taken as criteria for the degree of the pyrylium character [46]. In general, the chemical shifts of the hydrogen in the on the H-7 proton (Table 1).

The 13

X-ray crystal structures

The molecular structures of compounds 2, 4 and 6 with the atom labeling scheme are displayed in Figs. S1 (see Supplementary material) compares their bond distances and angles, that are in accordance with previously reported structural data [START_REF] Ruiz | however, ferrocene is far from perfect as an internal reference[END_REF]. The exocyclic C-C bond lengths lie in the range 1.353(10) -1.370(10) Å, thus suggesting a weak pyrylium character [START_REF] Ruiz | however, ferrocene is far from perfect as an internal reference[END_REF]. In addition, the mean planes of the aromatic rings at C-2, C-6 and C-7 (this atom labelling refers to Fig. 1) are tilted with respect to the mean plane of the methylenepyran core with dihedral angles of 6.77, 19.37 and 34.65° for 2A, 6.22, 19.56 and 34.85° for 2B, 3.75, 14.81 and 18.23° for 4, and 17.60, 14.12 and 30.28° for 6, respectively. 24) 118.56 (19). 118.04 (17).

Complexes 4 and 6 contain the 1-ferrocenyl and 1,1"-ferrocenyl moiety, respectively. In compound 4, the iron atom is coordinated to the free and substituted cyclopentadienyl rings at ring centroid-iron distances of 1.661 and 1.642 Å, respectively, whereas in compound 6 the two ring centroid-iron distances are identical and equal to 1.650 Å, although one ring bears a donor methylenepyran substituent and the other an acceptor acetyl one. In each organometallic fragment, the two carbocyclic ligands are essentially parallel with ring centroid-iron-ring centroid angles of 177.5° for 4 and 177.6° for 6. Those metrical parameters clearly feature a linear sandwich structures with typical [ 5 -Fe- 5 ] coordination mode, and indicate that there is a Fe(II) oxidation state in each metallocene [47].

On the other hand, within both 4 and 6 the acyl units C( 10 reported values for keto-enol tautomers of -diketone derivatives [13][14][15][16][17][18][19]. In addition, the plane of the [OCCCO] framework is almost coplanar with both the substituted cyclopentadienyl ring and the phenylene ring, making dihedral angles of 6.22 and 7.02°, respectively, a situation that should allow partial conjugation between the two parts of the molecule. Lastly, the crystal packing of ( 4) is effected by intermolecular interactions between an hydrogen atom and the carbonyl oxygen atom (C( 6)-H(6

) … O(1) = 3.454 Å, H(6) … O(1) =
2.666 Å and C( 6)-H(6) … O(1) = 140.8°; symmetry code: 1-x, 1-y,-z ) (Supplementary material, Fig. S1).

2-3-Electrochemical studies

The redox behavior of these new organic and organometallic compounds 2-4, 6 and 7 was investigated by cyclic voltametry in dichloromethane containing 0. For all of the compounds, an irreversible anodic wave, classically observed for methylenepyran derivatives [START_REF] Ruiz | however, ferrocene is far from perfect as an internal reference[END_REF], was observed between -0.05 and 0.34V vs ferrocene/ferricenium (Cp 2 Fe +/0 ) redox couple (Table 2). For ( 2)-( 4 Data from Ref. [START_REF] Ruiz | however, ferrocene is far from perfect as an internal reference[END_REF].

Moreover, on the reverse scan of the cyclic voltamogramm, a new irreversible cathodic wave was observed between -0.69 and -0.86 V vs Cp 2 Fe +/0 that is not observed when the scan is directly run in reduction (Fig. 5). This electrochemical behaviour is consistent with monoelectronic oxidation followed by rapid dimerization, as previously demonstrated for ferrocenylmethylenepyran compounds [40a,b]. Indeed, the first oxidation generates a radical cation which undergoes an intermolecular C-C bond coupling to form a dimer. The latter is detected on the back scan with the observation of an irreversible reduction wave. Finally, when the scan direction was reversed toward more positive potentials, after the appearance of the reduction wave, the voltamogram was identical to the one obtained in the initial scan. This observation suggests that the product formed upon oxidation is reduced back to the original compound. This kind of behaviour, already observed by us [START_REF] Ruiz | however, ferrocene is far from perfect as an internal reference[END_REF], has also been observed in other molecular systems [50], and suggests that C-C bond making/breaking is reversibly induced upon electron transfer.

Finally, for the ferrocenyl-containing compounds, two successive reversible one-electron oxidation waves for 6 and 7 and one reversible two-electron oxidation for 4 (based on current ratio) were observed following the first oxidation process. Cyclic voltammograms of 4 and 7

are displayed in fig. 5, whereas that of 6 is presented in Fig. S4 (Supplementary material).

Compared to the precursor compound 5, a positive shift is observed for 6 and 7, due to the presence of the electron withdrawing substituent. As previously shown for the ferrocenylmethylenepyran 5, these oxidation waves may be assigned to the ferrocenyl groups of the dicationic dimer formed after the first oxidation. In the particular case of 4, this behaviour suggests that there is no electronic communication between the two ferrocenyl fragments [51].

Conclusions

In this contribution, a new family of electron-rich methylenepyran derivatives has been successfully synthesized and fully characterized, and their redox properties thoroughly investigated. All the compounds described in this work contain the 4-[ (2,6- were also authenticated by single-crystal X-ray diffraction analysis. response. On the other hand, the new unsymmetrical electron-rich methylenepyran-containing 1,3-diketones 3, 4 and 7 are also expected to be strong chelating agents toward transition metal ions, and may also serve as valuable building blocks in the construction of polydentate Schiff base ligands, as well as in the synthesis of heterocyclic compounds such as pyrazoles which are known to have a broad spectrum of biological activities.

Experimental Section

General Experimental Methods

Manipulations of air-sensitive compounds were performed under a dry dinitrogen atmosphere using standard Schlenk techniques. Solvents were dried and distilled under dinitrogen by standard methods prior to use. [52] Chromatographic purification was performed with Silicagel 60 (0.063-0.200 µm). 2,6-diphenyl-4H-pyran-4-yl triphenylphosphonium tetrafluoroborate 1, [43] ferrocenylmethylenepyran 5, [40] and phenylmethylenepyran 8, [53] were synthesized according to published procedures. Methyl 4-formylbenzoate, n-butyllithium (2.5 M in hexanes), acetylferrocene, potassium tert-butoxide, 4-methoxyacetophenone, diisopropylamine and petroleum ether 40-60 were purchased from Aldrich and used as received.

Solid-state FT-IR spectra were recorded on a Perkin Elmer model 1600 FT-IR or 1000 FTIR spectrophotometer using KBr disks, in the range 4000-450 cm -1 . 1 H and 13 quoted against the ferrocene-ferricenium redox couple; ferrocene was added as an internal standard at the end of each experiment [54]. Melting points were measured in evacuated capillaries on a Kofler Bristoline melting point apparatus and are uncorrected. (2,6-diphenyl-4H-pyran-4-ylidene) (m, 6 H, H-23,24,25 and H-63,64,65), 7.44 (d, 3 J H,H = 7.8 Hz, 2 H, H-9,13), 7.79 (t, 3 J H,H = 6.8 Hz, 4 H, -H22,26 and H-62,66), 7.85 (d, 3 J H,H = 7.8 Hz,2 H,12). 13 C NMR (100 MHz, CD 3 COCD 3 , 25°C):  52.5 (CH 3 ), 102.9 (C-3), 109.9 (C-5), 114.8 (C-7), 125.8, 126.3, 127.9, 128.8, 130.0, 130.1, 130.6, 130.9 (C-H arom), 131.0, 132.5, 134.2, 134.3 (C quat ), 144.7 (C-11), 152.5 (C-6), 154.8 (C-2), 167.5 (C=O).

Synthesis of methyl 4-[

4.3.

Synthesis of 1-{4-[(2,6-diphenyl-4H-pyran-4-ylidene)methyl]phenyl} -3-(4methoxyphenyl) propane -1,3-dione (3) A Schlenk tube was charged with a magnetic stir bar, 4-methoxyacetophenone (0.220 g, 1.46 7), 124.5, 124.8, 126.9, 127.5, 128.7, 129.3, 129.6, (C-H arom) 3), 6.80 (s, 1 H, H-5), 7.43-7.45 (m, 6 H, H-23,24,25 and H-63,64,65), 7.76-7.69 (m, 4 H,H-22,26 and H-62,66). 13 4.6. Synthesis of 1- (1,3-dioxobutyl)-1'-[(2,6-diphenyl-4H-pyran-4-ylidene)methyl] ferrocene (7) A Schlenk tube was charged with a solution of di-isopropylamine (576 µL, 4.10 mmol) in diethyl ether (4.0 mL) to which was added dropwise n-butyl lithium (1.6 mL, 4.0 mmol) at 0 °C. The resulting mixture was stirred for 1 h before solid sample 1-acetyl-1"-Kaptan loop. The loop was transferred to the diffractometer, centered in the beam, and cooled by a nitrogen flow low-temperature apparatus that had been previously calibrated by a thermocouple placed at the same position as the crystal. The structures were solved by direct methods using SIR97 program [55], and then refined with full-matrix least-square methods based on F 2 (SHELXL-97) [56], with the help of WINGX program [57]. All non-hydrogen atoms were refined with anisotropic atomic displacement parameters. Hydrogen atoms were finally included in their calculated positions. The disorder observed for the carbon atoms of the free cyclopentadienyl ring in 4 was modelled using two positions per carbon with fixed 0.71 and 0.29 occupancy factors for each carbon. A summary of the details about crystal data, collection parameters and refinement are documented in Table 3, and additional crystallographic details are in the CIF files. ORTEP and Ball-and-Stick views are generated using OLEX2 [58].

  [42a]. The stirring of a THF suspension of the desired salt [R-C(=O)CH 2 ] -K + (R = 4-MeO-C 6 H 4 or Cp-Fe(η 5 -C 5 H 4 )-, in situ generated by deprotonation of 4-methoxyacetophenone or acetylferrocene with t-BuO -K + , in the presence of 2 equivalents of the 4-methylbenzoate methylenepyran precursor 2 for 15h at room temperature, yielded the organic diketone 4-MeO-C 6 H 4 -C(=O)CH=C(OH)(p-C 6 H 4 -CH=pyran) (3), and the organometallic counterpart Cp-Fe(η 5 -C 5 H 4 )-C(=O)CH=C(OH)(p-C 6 H 4 -CH=pyran) (4), both -diketones isolated as orange and dark-red crystalline solids, respectively, in 50% yield after work up and recrystallization (Scheme 1).

Fig. 1

 1 Fig.1Labeling scheme used for NMR assignments.

  3/5-position tend to shift downfield as the contribution of pyrylium resonance form increases in the ground-state structure of a compound. Thus, from comparison of the observed H-3/H-5 chemical shift values of compounds 6 and 7 with those, more deshielded, of compounds 2-4, it apears that the ferrocenylmethylenepyran derivatives 6 and 7 have a lower pyrylium character. In 2-4 the exocyclic C-7 carbon is substituted by an electron withdrawing p-C 6 H 4 -C(=O)R group whereas in 6 and 7 it bears the electron releasing ferrocenyl moiety. The electronic nature of those substituents has also a profound deshielding effect, up to 0.6 ppm,

  2, 3 and 4, respectively, with selected bond distances and angles listed in their respective captions. The three complexes cristallize in the monoclinic centrosymmetric space group P2 1 /n. Two crystallographically independent molecules (2A and 2B) are found in the asymmetric unit cell of 2 while that of 4 and 6 contains each a single molecule. The single-crystal X-ray diffraction studies confirm both the monomeric nature and that each compound consists of a [(2,6-diphenyl-4H-pyran-4-ylidene)methyl] group linked to an aromatic C 6 -ring in the case of the -diketone 4 and of its precursor 2, and to an acetylferrocene moiety in the case of 6. Whatever the substituent at the exocyclic methine carbon atom, the methylenepyran cores remain structurally very similar with alternating single and double C-C bonds. Table

Fig. 2

 2 Fig. 2 Molecular structure of 2 with the atom numbering scheme; only molecule 2A is shown. Hydrogen atoms have been omitted for clarity. Thermal ellipsoids are drawn at 50% probability. Selected bond distances [Å] and angles [°]: O(1)-C(1) 1.436(8), O(1)-C(2) 1.348 (9), O(2)-C(2) 1. 197(9), C(9)-C(10) 1.370(10), C(11)-C(12) 1.338(10), C(13)-C(14) 1.336(9), O(3)-C(12) 1.377(8), O(3)-C(13) 1.376(8); C(1)-O(1)-C(2) 115.1(6), O(1)-C(2)-O(2) 123.8(7), O(2)-C(2)-C(3) 124.4(8), C(6)-C(9)-C(10) 127.8(7), C(9)-C(10)-C(11) 126.8(7), C(9)-C(10)-C(14) 120.1(7), C(10)-C(11)-C(12) 122.7(7), C(10)-C(14)-C(13) 121.7(7), O(3)-C(12)-C(11) 121.4(7), O(3)-C(13)-C(14) 122.9(6), O(3)-C(12)-C(15) 111.9(6), O(3)-C(13)-C(21) 111.2(6), C(12)-O(3)-C(13) 118.0(6).

Fig. 3

 3 Fig. 3 Molecular structure of 4 with the atom numbering scheme. Hydrogen atoms have been omitted for clarity. Thermal ellipsoids are drawn at 50% probability. Selected bond distances

Fig. 4

 4 Fig. 4 Molecular structure of 6 with the atom numbering scheme. Hydrogen atoms have been omitted for clarity. Thermal ellipsoids are drawn at 50% probability. Selected bond distances [Å] and angles [°]: C(5)-C(6) 1.477(3), C(6)-O(8) 1.219(3), C(6)-C(7) 1.506(4), C(14)-C(15) 1.357(3), C(16)-C(17) 1.335(3), C(19)-C(20) 1.335(3), O(18)-C(17) 1.389(3), O(18)-C(19) 1.385(3); O(8)-C(6)-C(5) 121.1(2), O(8)-C(6)-C(7) 121.2(2), C(13)-C(14)-C(15) 127.8(2), C(14)-C(15)-C(16) 120.8(2), C(14)-C(15)-C(20) 126.5(2), C(15)-C(16)-C(17) 122.8(2), C(15)-C(20)-C(19) 122.4(2), O(18)-C(17)-C(16) 121.57(19), O(18)-C(19)-C(20) 122.26(19),

  with their corresponding attached cyclopentadienyl rings C(6) … C(10) and C(1) … C(5) with dihedral angles of 5.42 and 7.66°, respectively. This is typical of the conformations observed in acyl ferrocenes Fc-COR[41,48]. Additionally, in complex 6, the acetyl group exhibits a classical O(1)-C(6)-C(7) angle of 121.2(2)°[41,48], and in the two complexes, the C-C and C-Fe bond distances of the ferrocene sandwiches as well as the C=O bond distance fall all within the range of standard values [49]. In compound 4, the angles at C(11), C(12) and C(13) of the [O(1)-C(11)-C(12)-C(13)-O(2)] central core are of 120.7(2), 120.1(2) and 120.3(2)°, respectively, that are idealized value expected for a sp 2 -hybridized carbon atom. The O(1)-C(11), C(11)-C(12), C(12)-C(13) and C(13)-O(2) bond lengths (see caption of Fig. 3) observed in this planar skeleton correspond to alternating double-, single-, double-and single-bonds [49], exhibiting partial delocalization of the O=C-C=C-O system. Those metrical parameters are consistent with a keto-enol tautomeric form for 4, with an intramolecular O(1) … H-O(2) hydrogen bonding interaction which closes a six-membered pseudo-aromatic ring through the resonant •••O=C-C=C-OH••• fragment [18]. The O•••O separation is equal to 2.450 Å, in accordance with previously

  ), values of the oxidation potential (0.23-0.34 V) are comparable to that measured for the parent phenylmethylenepyran compound 8 (0.23 V)[40c]. For the organometallic derivatives 6 and 7, only slight variation of the oxidation potential was observed when compared to that of the parent ferrocenylmethylenepyran derivative 5, since the oxidation potential of this compound was observed at -0.15 V [40b]. According to the DFT calculations carried out for 5, which shows that the three highest occupied MOs have a large metal contribution [40c], the main difference between 2, 3, 4, 8 and 5, 6, 7 may originate from the nature of the oxidized site that seems to be the pyran and the ferrocenyl units, respectively.

Fig. 5

 5 Fig. 5 Cyclic voltammograms of compounds 4 (a) and 7 (b) at a Pt disk working electrode, in CH 2 Cl 2 / 0.1 M [n-Bu 4 N][BF 4 ] at 298 K. Redox potentials are quoted vs. the ferrocene/ferricenium couple (Cp 2 Fe +/0 ).

   NMR studies clearly show that both -diketones 3 and 4 do exist solely as their keto-enol tautomeric form in solution, wheras a mixture of keto-enol and -diketone tautomers was observed for 7 in a 73:27 spectroscopic ratio. Enolization takes place exclusively away from the anisyl or ferrocenyl group, suggesting the existence of a resonance driving force instead of an electronic driving force to explain the dominance of the R-C(O)CH=C(OH)-form (R = anisyl, Fc). This is supported by the crystal structure of complex 4, where the six-membered pseudo-aromatic keto-enol ring is coplanar with the cyclopentadienyl and phenylene ring substituents, thus allowing a partial conjugation between the two redox active parts of the molecule. Owing to their electron-rich nature, the methylenepyran compounds 2-4, 6 and 7, studied by cyclic voltammetry are readily oxidized to radical cations. The oxidation potential values are markedly affected by the position of the ferrocenyl ring toward the methylenepyrane fragment. The unstable radical cation evolves by dimerization in bispyrylium systems that regenerate the starting material upon reduction. These systems, undergoing reversible C-C bond making/breaking upon electron transfer, might be interesting in the construction of molecular switches or memories based on their electrochemical

  Chemical shifts () are reported in parts per million (ppm) and referenced to the residual deuterated solvent peaks. Coupling constants (J) are reported in Hertz (Hz), and integrations are reported as number of protons. The following abbreviations are used to describe peak patterns: br = broad, s = singlet, d = doublet, t = triplet, m = multiplet. 1 H and13 C NMR chemical shift assignments are supported by using COSY, HMQC and HMBC NMR techniques, and are given according to the numbering scheme of Figure 1. High resolution electro spray ionization mass spectra (ESI-MS) were obtained at the CRMPO (Rennes) with a WATERS Q-TOF spectrometer. Elemental analyses were conducted on a Thermo-FINNIGAN Flash EA 1112 CHNS/O analyzer by the Microanalytical Service of the CRMPO (Rennes). Cyclic voltammetry experiments were performed with a µ -AUTOLAB III potentiostat monitored by a computer. A three-electrode cell was used, equipped with a platinum wire auxiliary electrode, a glassy carbon or a platinum working electrode, Ag/AgCl non aqueous as reference or silver wire as a quasi-reference electrode. All the potential are

  C NMR (125 MHz, CDCl 3 , 25°C):  27.7 (CH 3 ), 69.3, 70.0

Table 1 1

 1 H NMR spectral data for the methyne protons of the methylenepyran core a

	Compd  H-3	 H-5	 H-7
		(ppm)	(ppm)	(ppm)
	2	6.64	7.06	5.96
	3	6.46	7.07	5.97
	4	6.49	7.09	5.98
	6	6.34	6.80	5.46
	7-enol	6.27	6.78	5.38
	7-keto	6.35	6.79	5.45

a recorded at 25 °C in CDCl 3 .

  C NMR spectra of compounds 2-4, 6 and 7, obtained at 25 °C in CDCl 3 , are fully consistent with the proposed structures (see Experimental Section). For instance, the spectrum of 7 confirms the existence of the keto-enol/-diketone tautomeric mixture. The methyne carbon resonates at  97.6 ppm for the keto-enol form, while it shows up at  56.6 ppm for the -diketone derivative. At the same time, the acetyl carbonyl carbon experiences a downfield shift from  187.1 to 202.3 ppm, while the ferrocenoyl carbonyl carbon is slightly downfield shifted by 5.6 ppm. In addition, the13 C NMR of the new compounds exhibited the five resonances expected for the five magnetically non-equivalent carbons of the methylenepyran core (see Experimental Section). For example, the spectrum of the diketone 3 showed the quaternary C-2, C-4 and C-6 carbons at  153.6, 131.5 and 151.6 ppm, respectively. The

vinylic C-3 and C-5 carbons were seen at  102.0 and 108.7 ppm, respectively, and the exocyclic C-7 carbon resonated at  113.2 ppm. Moreover, the phenyl carbons showed up as two sets of four closely spaced singlets at  124.6/125.0, 128.6/128.7, 129.3/129.6 and 133.0/133.4 ppm for the ortho, meta, para and quaternary carbons, respectively. One can also note that the chemical shift of the C-7 carbon is sensitive to the electronic nature of its substituent, with peaks observed at  114.8, 113.2 and 113.0 ppm in 2, 3 and 4, respectively, and at  109.3, 108.9 and 108.8 ppm in 6, 7-enol and 7-keto, respectively.

Table 2

 2 Electrochemical data for compounds 2-8 a recorded in CH 2 Cl 2 / 0.1 M n-Bu 4 N + BF 4 -at 0.1 V s -1 , at 298 K; redox potentials quoted in V vs. the ferrocene/ferricenium couple (Cp 2 Fe +/0 ).

	Compd	E ox (1) b	E red	c	E ½ (2)	E ½ (3)
	2	0.34	-0.82
	3	0.32	-0.82
	4	0.23	-0.86	0.25 (2 e -)
	5 d	-0.15	-0.76	0.12	0.28
	6	-0.02	-0.83	0.37	0.47
	7	-0.05	-0.77	0.33	0.44
	8 d	0.23	-0.86

a b

Irreversible peak. c Irreversible peak on the reverse cathodic scan.

d

  C NMR spectra were recorded with either a Bruker Avance III 400 spectrometer at the Universidad Federico Santa María (Valparaíso, Chile), or a Bruker AV 500 at the Centre Régional de Mesures Physiques de l"Ouest (CRMPO, Rennes, France) or a Bruker DRX 500 spectrometer at the Service Commun de Recherche de Résonance Magnétique Nucléaire et de Résonance Paramagnétique Electronique de l"Université de Bretagne Occidentale (Brest, France).

  methyl]benzoate(2) To a Schlenk tube containing a stirred solution of 2,6-diphenyl-4H-pyran-4-yl triphenylphosphonium tetrafluoroborate salt 1(2.90 g, 4.98 mmol) in THF(40 mL), cooled to -75 °C, was added dropwise n-butyllithium(2.30 mL, 5.78 mmol).

		The solution turned
	black. After 15 min of stirring, solid methyl 4-formylbenzoate (0.818 g, 4.98 mmol) was
	slowly added. The reaction mixture was stirred at -75 °C for 4 h. Then, the solvent was
	evaporated under reduced pressure at room temperature (r.t.). The solid residue was dissolved
	in a minimum amount of dichloromethane (DCM) and absorbed on a column packed with
	silica gel (grade 60). Elution with petroleum ether-DCM mixture (1:1) produced the release
	of a yellow band that was collected. The solvent was evaporated under reduced pressure and
	the product was recrystallized from DCM-hexane mixture (1:1), affording yellow
	microcrystals of 2 (1.40 g, 75% yield). A crystal from this crop was used for X-ray structure
	determination. M.p. 130-132 °C. C 26 H 20 O 3 • 0.05 CH 2 Cl 2 (384.2 g mol -1 ): Calcd. C 81.36, H
	5.21; found C 81.42, H 5.23. IR (KBr, cm -1 ): 1715 (s) (C=O), 1656 (m) (C=C), 1595, 1581,
	1493, 1447, (C=C), 1270 (O-C) .	1 H NMR (400 MHz, CD 3 COCD 3 , 25°C):  3.75 (s, 3 H,
	CH 3 ), 5.96 (s, 1 H, H-7), 6.64 (d, 4 J H,H = 1.75 Hz, 1 H, H-3), 7.06 (d, 4 J H,H = 1.75 Hz, 1 H, H-
	5), 7.38

  The solvent was evaporated under reduced pressure and the product was recrystallized by slow diffusion of petroleum ether in a DCM solution of the product, affording 0.364 g (50% yield) of dark red microcrystals of 3. M.p. 160-163 °C.C 34 H 26 O 4 (498.57 g mol -1 ): calcd. C 81.91, H 5.26, O 12.84; found C 81.55, H 5.15, O 12.62. 6.49 (s, 1 H, H-3), 7.09 (s, 1 H, H-5),7.41-7.51 (m, 8 H, H-9,13, H-23,24,25 and H- 63,64,65), 7.79 (d, 3 J H,H= 7.3 Hz, 4 H, H-22,26 and H-62,66), 7.93 (d, 3 J H,H= 7.8 Hz, 2 H,12),16.82 (s, 1 H, OH).13 C{ 1 H} NMR (125MHz, CDCl 3 , 25°C):  68.6 (C 5 H 4 ), 70.3 (C 5 H 5 ), 72.3 (C 5 H 4 ), 77.3 (C ipso C 5 H 4 ), 93.2 (=C-H acac), 101.8 (C-3), 108.5 (C-5), 113.0 (C-

	mmol), potassium tert-butoxide (0.250 g, 2.23 mmol) and 3.0 mL of THF. The reaction mixture was vigourously stirred for 15 min before a solid sample of compound 2 (1.10 g, 2.89 mmol) was slowly added. After 10 min of stirring, 2.0 mL of THF were additionally added and the vigorous stirring was continued for 15 h at r.t. The reaction was quenched with water and partitioned between water and DCM (3 x 50 mL). The combined organic extracts were dried over MgSO 4 , concentrated and adsorbed on a column packed with silica gel. Elution with petroleum ether-DCM mixture (2:8) produced the release of an orange band that was 1598 (m) (C=O) and/or (C=C), 760 (m) (C-H). 1 H NMR (500 MHz, CDCl 3 , 25°C):  3.91 (s, 3 H, CH 3 ), 5.97 (s, 1 H, H-7), 6.46 (d, 4 J H,H = 1.75 Hz, 1 H, H-3), 6.81 (s, 1 H, CH acac), 6.99 (d, 3 J H,H = 8.9 Hz, 2 H, C 6 H 4 -OCH 3 ), 7.07 (d, 4 J H,H = 1.75 Hz, 1 H, H-5), 7.47 (t, 3 J H,H = 7.5 Hz, 2 H, H-24,64), 7.46 (m, 3 J H,H = 7.5 and 7.8 Hz, 4 H, H-23,25 and H-63,65), 7.49 (d, 3 J H,H = 8.5 Hz, 2 H, H-9,13), 7.77 (d, 3 J H,H = 7.8 Hz, 4 H, H-22,26 and H-62,66), 7.97 (d, 3 J H,H = 8.5 Hz, 2 H, H-10,12), 7.99 (d, 3 J H,H = 8.9 Hz, 2 H, C 6 H 4 -OCH 3 ), 17.09 (s, 1 H, OH). 13C { 1 H} NMR (125 MHz, CDCl 3 , 25°C):  55.5 (CH 3 ), 92.0 (C-H acac), 102.0 (C-3), 108.7 (C-5), 113.2 (C-7), 113.9 (C-H C 6 H 4 -OCH 3 ), 124.6 (C-22,26), 125.0 (C-62,66), 127.4 (C-10,12), 127.6 (C-9,13), 128.5 (C quat C 6 H 4 -C=O), 128.7 (C-63,65), 128.7 (C-23,25), 129.2 (C-H C 6 H 4 -OCH 3 ), 129.3 (C-64), 129.6 (C-24), 131.5 (C-4), 132.0 (C-11), 133.0 (C-61), 133.2 (C-21), 143.0 (C-8), 151.6 (C-6), 153,6 (C-2), 163.1 (C-OCH 3 ), 183.6 (C-OH), 185.6 (C=O). 4.4. Synthesis of 1-(4-((2,6-diphenyl-4H-pyran-4-ylidene)methyl)phenyl)-3-(ferrocenyl)propane-1,3-dione (4) A Schlenk tube was charged with a magnetic stir bar, acetylferrocene (0.32 g, 1.457 mmol), potassium tert-butoxide (0.250 g, 2.23 mmol) and 3.0 mL of THF. After 15 min of stirring, a light brown precipitate formed and the reaction mixture was vigorously stirred for 2 h before a solid sample of compound 2 (1.1 g, 2.89 mmol) was slowly added. After 10 min of stirring, 2.0 mL of THF were added and the vigorous stirring was continued for 15h. The reaction was quenched with water and partitioned between water and DCM (3 x 50 mL). The combined organic extracts were dried over MgSO 4 , concentrated and adsorbed on a column packed with silica gel. Elution with petroleum ether-DCM mixture (4:6) produced the release of a dark red band that was collected. The solvent was evaporated under reduced pressure and the product was recrystallized by slow diffusion of petroleum ether into a DCM solution of the product, affording 0.420 g (50% yield) of dark red microcrystals of 4. A crystal from this crop was used for X-ray structure determination. M.p. 90-93 °C. C 37 H 28 O 3 Fe • 0.1CH 2 Cl 2 (584.53 g mol -1 ): calcd. C 76.16, H 4.82; found C 76.56, H 4.86. IR (KBr, cm -1 ): 3446 (w) asym (-OH), collected. IR (KBr, cm -1 ): 3414 (w) asym(-OH), 3100 (w) (C-H arom), 2900 (w) (C-H aliph), 1658 (m), 3088 (w) (C-H arom), 2965 (w) (C-H aliph), 1656 (m), 1578 (m) (C=O) and/or (C=C), 764

(m)

(C-H)

.

1

H NMR (500 MHz, CDCl 3 , 25°C):  4.23 (s, 5 H, C 5 H 5 ), 4.59 (br t, 3 J H,H = 1.6 Hz, 2 H, C 5 H 4 ), 4.90 (br t, 3 J H,H = 1.6 Hz, 2 H, C 5 H 4 ), 5.98 (s, 1 H, H-7), 6.41 (s, 1 H, C-H acac),

  Cl 2 (100 mL), under N 2 at 0°C. The reaction mixture was stirred for 2 h, quenched with water (100 mL), and extracted with DCM. The organic phase was collected, neutralized with a 0.1 M aqueous solution of Na 2 CO 3 , and dried over MgSO 4 . H NMR (500 MHz, CDCl 3 , 25°C):  2.36 (s, 3 H, CH 3 ), 4.29 (t, 3 J H,H = 1.6 Hz, 2 H, C 5 H 4 ), 4.43 (t, 3 J H,H = 1.6 Hz, 2 H, C 5 H 4 ), 4.49 (t, 3 J H,H = 1.8 Hz, 2 H, C 5 H 4 COCH 3 ), 4.76 (t, 3 J H,H = 1.8 Hz, 2 H, C 5 H 4 COCH 3 ), 5.46 (s, 1 H, H-7), 6.34 (s, 1 H, H-

	, 131.2 (C-4), 132.9, 136.6,
	137.2 (C-11, C-21, C-61), 142.5 (C-8), 151.2, 153.2 (C-2/C-6), 178.4 (C-OH), 194.8 (C=O).
	4.5. Synthesis of 1-acétyl-1'-[(2,6-diphenyl-4H-pyran-4-ylidene)methyl] ferrocene (6)
	A Schlenk tube was charged with a magnetic stirbar, acetyl chloride (0.26 mL, 3.50 mmol),
	aluminum trichloride (0.470 g, 3.50 mmol) and DCM (20.0 mL). The resulting mixture was
	stirred for 2 h at rt and added dropwise to a solution of ferrocenyl-methylenepyran 5 (0.500 g,
	1.16 mmol) in freshly distilled CH 2

The solvent was evaporated under reduced pressure to give compound 6 as a red microcrystalline powder (0.350 g, 61 % yield). The product was recrystallized by slow diffusion of diethyl ether into a DCM solution of the complex. M.p 116-118 °C. HRMS-ESI + (based on 56 Fe) C 30 H 24 O 2 NaFe [M + Na] m/z calcd: 495.1023; found: 495.1023 (0 ppm). IR (KBr, cm -1 ): 1657 (s) (C=O), 1601 (w), 1579 (w) (C=C), 1493 (w), 1448 (w) (C-H), 822 (br), 762 (s), 687 (s) (C-H). 1

Table 3

 3 Crystallographic data, details data collection and structure refinement parameters for compounds 2, 4 and 6

			2	4	6
	Empirical formula	C 52 H 40 O 6	C 37 H 28 FeO 3	C 30 H 24 FeO 2
	Formula mass, g mol -1	760.84	576.44	472.34
	Collection T, K	150(2)	150(2)	150(2)
	Crystal system	Monoclinic	Monoclinic	Monoclinic
	space group	P2 1 /n	P2 1 /n	P2 1 /n
	a (Å)		7.0936(14)	12.5310(8)	5.8457(7)
	b (Å)		30.623(6)	5.8917(3)	31.725(5)
	c (Å)		17.892(3)	36.617(2)	11.9626(17)
	 (°)		101.327(6)	98.574(3)	96.648(5)
	V (Å 3 )		3810.9(12)	2673.2(3)	2203.6(5)
	Z		4	4	4
	D calcd (g cm -3 )	1.326	1.432	1.424
	Crystal size (mm)	0.32 x 0.31 x 0.07	0.6 x 0.14 x 0.09	0.6 x 0.09 x 0.08
	F(000)		1600	1200	984
	abs coeff (mm -1 )	0.086	0.603	0.711
	 range (°)	2.93 to 27.48	3.04 to 27.48	3.09 to 27.48
	range h,k,l	-39/39, -23/23	-16/16, -5/7, -47/47	-4/7, -41/41, -15/15
	No. total refl	55291	23189	17651
	No. unique refl	8559	6099	5002
	Comp. to  max (%)	97.3	99.3	98.9
	Max/min transmission	0.994/0.833	0.947/0.761	0.945/0.843
	Data/Restraints/Parameters	8559/0/448	6099/30/387	5002/0/299
	Final R	R 1 = 0.0582	R 1 = 0.0426	R 1 = 0.0416
	[I>2(I)]	wR 2 = 0.1252	wR 2 = 0.0885	wR 2 = 0.0870
	R indices (all data)	R 1 = 0.1450	R 1 = 0.0769	R 1 = 0.0660
			wR 2 = 0.1598	wR 2 = 0.1014	wR 2 = 0.0967
	Gof / F	2	1.016	1.025	1.058
	Largest diff. Peak/hole (eÅ -3 )	0.265/-0.276	0.307/-0.495	0.377/-0.338

Acknowledgments

The authors thank Drs S. Sinbandhit and P. Jehan (CRMPO, Rennes) for NMR and HRMS experiments, respectively. We are to N. Kervarec, S. Cerantola and G. Simon for recording NMR spectra (Service Commun de Recherche de RMN et de RPE, Université de Bretagne Occidentale, Brest). This research has been performed as part of the Chilean-French International Associated Laboratory for ""Inorganic Functional Materials"" (LIAMIF-CNRS N°836). Financial support from the Fondo Nacional de Desarrollo Científico y Tecnológico [FONDECYT (Chile), grant no. 1090310 (C.M. and D.C.)], the Vicerrectoría de Investigación y Estudios Avanzados, Pontificia Universidad Católica de Valparaíso, Chile (C.M. and D.C.), the CNRS, the MESR and the Université de Rennes 1 is gratefully acknowledged. N.N. thanks the CONICYT (Chile) for support of a graduate fellowship and the French Embassy in Chile for the 2011 scholarship awarded doctoral internship.

Appendix A. Supplementary material

CCDC 949438 -949440 contains the supplementary crystallographic data for this paper. These data can be obtained free of charge from The Cambridge Crystallographic Data Centre via www.ccdc.cam.ac.uk/data_request/cif.

Appendix B. Supplementary material

Bond distances and angles of the methylenepyran core for complexes 2, 4, and 6; packing diagram for 4 and cyclic voltammograms for complexes 2, 3, and 6.