Elena Pizzuto

Paolo Rossini

Marie-Anne Sallandre

Erin Wilkinson

Deixis, Anaphora and Highly Iconic Structures: Crosslinguistic Evidence on American (ASL), French (LSF) and Italian (LIS) Signed Languages 1

 Lombardi Vallauri [2004/to appear], for a recent overview).

We focus on two major classes of dectic-anaphoric reference devices that have been described in SL. The first, hereafter referred to as the 'standard' class has been rather extensively investigated, and is realized through manual and visual indexes which establish marked positions in space, often called "loci", where referents can be symbolically assigned (for overviews highlighting typological uniformity across SL with respect to this basic mechanism see, among others, Cuxac,

Sign Languages: spinning and unraveling the past, present and future. TISLR9, forty five papers and three posters from the 9o. Theoretical Issues in Sign Language Research Conference, Florianopolis, Brazil, December 2006. (2008) R. M. de Quadros (ed.). Editora Arara Azul. Petrópolis/RJ. Brazil. http://www.editora-arara-azul.com.br/EstudosSurdos.php. Pizzuto, 2004/to appear). Thus, to introduce a referent in discourse, a signer can produce a standard (or "frozen") manual sign 2 for the referent, and deictically mark it in the signing space via a manual and/or a gaze pointing, and/or also via morphological alteration of the sign's place of articulation (which may or may not be accompanied by visual indexes), thereby establishing a position in space (or 'locus') for the referent symbolized. Anaphoric reference is then made reindexing roughly the same point in space via visual or manual pointings (see 1.1 for more details and one illustrative example).

However, as noted elsewhere [START_REF] Pizzuto | Deixis, anaphora and person reference in signed languages[END_REF]/to appear), deictic-anaphoric reference is also produced, in SL, via complex manual and nonmanual units which are neither pointing signs, nor are they listable as standard signs. These units exhibit highly iconic features and are marked by specific eye-gaze patterns which distinguish them from standard signs. Throughout this paper we will refer to these units as Highly Iconic Structures (HIS) or 'Transfers', after Cuxac (1985;[START_REF] Cuxac | Fonctions et structures de l'iconicité des langues des signes[END_REF][START_REF] Cuxac | La Langue des Signes Française (LSF). Les voies de l'iconicité[END_REF]. Aside from specific eye-gaze patterns, HIS may be composed of: (1) manual forms encoding perceptually salient features of the referents/ referential relations, most frequently described in the SL literature with different terms such as "classifiers", "productive morphemes", "polysynthetic" or "polycomponential" signs; (2) marked facial expressions, and/or directional modifications of head, shoulders, whole trunk --usually described in the literature as "role-shifting devices" but also with other terms (see section 1.1 below for more discussion). As we will illustrate shortly hereafter, different subtypes of HIS can be combined among themselves, or with standard signs, to simultaneously encode information on two (or even more) referents, hence allowing the specification of deictic-anaphoric reference in a multilinear fashion that appears to be unique of the visual-gestural modality.

Although the manual and nonmanual devices mentioned above have been described from different perspectives, and with different terminologies, there is little or no information on their use in deictic-anaphoric reference operations, and/or on how they interact with the 'standard' devices mentioned above. Our study provides relevant evidence on this topic through a comparative examination of short narrative texts produced in three SL: American (ASL), French (LSF) and Italian (LIS). ASL and LSF are known to be historically related, while LIS has no certain relationship with either ASL or LSF 3 . The sample of language data we scrutinize thus allows us to 2 Standard signs are defined here, as in most SL literature, as those signs that are commonly listed in SL dictionaries, and are often described as constituting 'the frozen lexicon'. They are distinguished from the 'productive' highly iconic forms described shortly hereafter. 3 It must be recalled that, due to the absence of appropriate written documentation of SL and to the complex language transmission and variation phenomena proper of SL and of different communities of SL users [START_REF] Cuxac | La Langue des Signes Française (LSF). Les voies de l'iconicité[END_REF][START_REF] Fusellier-Souza | Sémiogenèse des langues des signes. Primitives conceptuelles et linguistiques des langues des signes primaires (LSP)[END_REF]2006), it is still very difficult to ascertain the historical links among SL using the same criteria that are applied in spoken/written language research. Thus, although there are no documented historical relationship between evaluate, albeit in part, the influence of language relations upon the phenomena investigated. If we were to find similarities only between ASL and LSF, this could be taken as evidence that the similarities identified can be attributed to the historical links between these two SL. If, however, we were to find that similar patterns hold across the three SL investigated, this evidence would suggest that similarities are grounded in more general features linked to the visual-gestural modality of language expression.

It is useful to clarify our theoretical framework and provide illustrative examples of the structures mentioned above.

Theoretical framework and illustrative examples of the structures we focus upon

The present study stems from, and brings together theoretical and empirical work independently developed, within our research groups, on SL morphology and on deixis and anaphora in SL as compared to spoken or verbal languages [START_REF] Pizzuto | Notes on Deixis and Anaphora in Spoken and Signed Languages[END_REF]2004/to appear;[START_REF] Pizzuto | Manual and Non-Manual Morphology in Italian Sign-Language: Grammatical Constraints and Discourse Processes[END_REF][START_REF] Wilkinson | Deaf and hearing signers with different signing experience; preliminary data from analyses of narrative texts ("Frog Story[END_REF], and on the crucial relevance that iconicity has in shaping SL lexicon, grammar, discourse [START_REF] Cuxac | Esquisse d'une typologie des Langues des Signes[END_REF][START_REF] Cuxac | Fonctions et structures de l'iconicité des langues des signes[END_REF][START_REF] Cuxac | La Langue des Signes Française (LSF). Les voies de l'iconicité[END_REF]Cuxac & Sallandre, 2004/to appear;[START_REF] Fusellier-Souza | Sémiogenèse des langues des signes. Primitives conceptuelles et linguistiques des langues des signes primaires (LSP)[END_REF]2006;[START_REF] Russo | Iconicity and productivity in sign language discourse: an analysis of three LIS discourse registers[END_REF][START_REF] Russo | Italian Sign Language (LIS) poetry: iconic properties and structural regularities[END_REF][START_REF] Sallandre | Les Unités du Discours en Langue des Signes Française. Tentative de Catégorisation dans le Cadre d'une Grammaire de l'Iconicité[END_REF][START_REF] Sallandre | Simultaneity in French Sign Language Discourse[END_REF]. An appropriate discussion of these theoretical foundations cannot be conducted here. We will only sketchily outline some of the major points, especially with respect to the HIS mentioned above. Before doing so, it is useful to consider briefly the 'standard' mechanism for deicticanaphoric reference, illustrated in Example (1) below with fragments taken from a LIS text reporting an ordinary event 4 .

1a LIS, on one hand, and ASL/LSF on the other hand, we cannot exclude that, at some point in past or recent history, these SL have been in contact more than we are at present able to ascertain. 4 From the 'Necklace theft' corpus [START_REF] Fabbretti | Scrivere e segnare. La costruzione del discorso nell'italiano scritto e nella Lingua dei Segni delle persone sorde[END_REF].

1c 1d 1e
(1) 'a colleague' [....] 'he, the colleague, he...'

The still videoclip in 1a shows a standard nominal sign meaning 'colleague' through which the signer deictically introduced in discourse this referent: the manual sign is dislocated at a marked position at the signer's right, and accompanied by a gaze pointing in the same direction.

Stills 1c-1e show how, at a later point in discourse, the signer anaphorically referred back to the same referent first via a manual index directed towards the same position in space previously marked (1c), then by a second instance of the sign 'colleague', this time articulated in an unmarked position in neutral space (1d, compare with 1a-1b), and then by a second index (meaning 'he, the colleague, he..').

This 'standard' mechanism for deictic-anaphoric reference in signed discourse interacts extensively with morphological modifications that different classes of verbs can undertake, altering their locations in space, which we will not consider here [START_REF] Cuxac | La Langue des Signes Française (LSF). Les voies de l'iconicité[END_REF]Pizzuto, 2004/to appear).

The point we wish to stress is that structures such as the above, described since early research on ASL (e.g. [START_REF] Friedman | On the semantics of space, time and person in American Sign Language[END_REF][START_REF] Klima | The Signs of Language[END_REF]Wilbur, 1979), appears to be very similar across several different SL of the world, and it seems plausible to assume that it is universal or nearly universal [START_REF] Mcburney | Pronominal reference in signed and spoken languages: are grammatical categories modality-dependent[END_REF][START_REF] Rathmann | Is verb agreement the same crossmodally?[END_REF]Pizzuto, 2004/to appear).

We turn now to briefly illustrate HIS and the theoretical model within which they are framed.

Based on extensive analyses of LSF discourse and grammar in a cross-linguistic framework, [START_REF] Cuxac | Esquisse d'une typologie des Langues des Signes[END_REF][START_REF] Cuxac | Fonctions et structures de l'iconicité des langues des signes[END_REF][START_REF] Cuxac | La Langue des Signes Française (LSF). Les voies de l'iconicité[END_REF] has proposed that all SL are grounded upon, and exploit a basic capacity that signers have in iconicizing their perceptual/practical experience of the physical world. One of the effects of this iconisation process is to endow SL with an additional semiotic dimension compared to verbal languages. In SL, unlike in verbal languages, there are two ways of signifying: either by 'telling and showing', thereby producing HIS or 'Transfers' that are unique of the signed modality, or by 'telling without showing', using the standard lexicon and pointings, and producing structures that are more comparable to those found in verbal languages.

These two ways of signifying mirror two different intents a signer can deliberately choose for articulating his/her discourse: an illustrative and a non-illustrative one. The operations signers perform when choosing an illustrative intent (and the resulting structures they produce) are defined "Transfers", and conceived as traces of cognitive operations whereby signers transfer their conceptualization of the real world into the four-dimensional world of signed discourse (the three dimensions of space plus the dimension of time).

The manual components of these complex structures are called 'proforms'. 'Proforms'

correspond to what, in most SL literature are defined as 'classifiers' (or with other terms previously mentioned -see [START_REF] Schembri | Rethinking" 'classifiers' in signed languages[END_REF] and the collected papers in Emmorey, for overviews). The difference between 'proforms' and 'classifiers', however, is not purely terminological but rather substantial: it is grounded on a linguistic model that attributes to iconicity a crucial, formal role in shaping SL discourse and grammar, on theoretical analyses showing the inadequacies of a 'classifier-analysis' for the elements under discussion, and on a detailed analysis of the distinctive formal and articulatory features that characterize the HIS within which proforms are embedded, most notably specific eye-gaze patterns [START_REF] Cuxac | Fonctions et structures de l'iconicité des langues des signes[END_REF][START_REF] Cuxac | La Langue des Signes Française (LSF). Les voies de l'iconicité[END_REF]. In contrast, analyses of these forms in terms of 'classifiers' focus primarily on the manual components, disregarding or underestimating the role that gaze patterns play in their specification.

Referring to [START_REF] Cuxac | Esquisse d'une typologie des Langues des Signes[END_REF][START_REF] Cuxac | La Langue des Signes Française (LSF). Les voies de l'iconicité[END_REF] in this paper we distinguish three main types of Transfers (but see [START_REF] Sallandre | Les Unités du Discours en Langue des Signes Française. Tentative de Catégorisation dans le Cadre d'une Grammaire de l'Iconicité[END_REF] for a much more detailed classification):

1. 'Transfers of Form and size' (TF) describe objects or persons according to their size or form (no process or role involved). The object is described by means of proforms. Gaze is oriented towards the hands, and facial expression specifies the form.

2. 'Transfers of Situation' (TS) involve the movement of an object or character (the agent, specified by the dominant hand) relative to a stable locative point of reference (specified by the non-dominant hand). The situation is shown as if the scene were observed from a distance. The signer keeps his/her distance relative to what s/he is conveying. Gaze is oriented towards the dominant hand and facial expression specifies the agent.

3. 'Transfers of Person' (TP) involve a role (agent or patient) and a process. The signer 'becomes' the entity to which s/he refers reproducing, in the course of the utterance, one or more actions carried out or sustained by this entity. The entities referred to are usually humans or animals but can also be inanimates.

The third type of Transfers, TP, have been defined in the literature with different terms including "role taking", "role shifting" [START_REF] Padden | Verbs and role-shifting in ASL[END_REF] or also, in earlier work ,"Body and Projected Body pronouns" [START_REF] Kegl | Pronominalization in American Sign Language[END_REF], "body markers" [START_REF] Pizzuto | Manual and Non-Manual Morphology in Italian Sign-Language: Grammatical Constraints and Discourse Processes[END_REF], with a primary focus on the nonmanual features they present (marked facial expressions, gazes, body postures).

As noted, a relevant feature of HIS is that subtypes of Transfers can be combined among themselves, or with standard signs, to encode information on two (or even more) referents in a multilinear, simultaneous fashion that has no parallel in speech. This phenomenon is called 'Double Transfer' (DT) in Cuxac's terminology (e.g. combining simultaneously a TP for specifying an agent, and a TS specifying locative information or also a second agent). Similar phenomena have been described from different perspectives and with different terminologies by several authors (e.g., among others, [START_REF] Dudis | Body partitioning and real-space blends[END_REF][START_REF] Russo | Iconicity and productivity in sign language discourse: an analysis of three LIS discourse registers[END_REF]; the collection of papers in Vermeerbergen, Leeson Crasborn, 2007). In this paper we refer to these phenomena as "Multiple

Reference" (MR) operations, and we assess their incidence in the signed narratives we analyzed.

Illustrations of these Transfer types are provided below. Examples ( 2) and ( 3) are taken from LSF narratives and highlight the differences between standard signs and HIS. Note how when producing the standard signs the signer's gaze is directed towards the interlocutor. In producing (2) 'tree' via a standard sign (2a) and via a TF (2b-2c)

HIS
Example (3) shows a standard sign (3a) and a TP (3b), both encoding the same conceptual content 'horse'. In the TP structure, all the manual and non manual features (gaze, facial expression, body and the hands) reproduce those of the embodied entity.

(3) 'horse' via standard sign (3a) and via a TP (3b)

Example (4) below illustrates three TS structures taken from, respectively, the LIS (4a), ASL (4b) and LSF (4c) narratives analysed for the present study. Both the LIS (4a) and the ASL (4b) example refer to 'the falling of a dog out of a windowsill'. The LSF example (4c) describes 'a horse jumping over a fence'. In all TS, gaze is towards the dominant, then the non-dominant hand.

The dominant hand expresses the agent with the process ('dog-falling', 'horse-jumping'), while the non-dominant hand expresses the locative, and the object implicated in the locative relation ('windowsill', 'fence'). The facial expression is congruent with the process represented.

(4) 4a: LIS 4b: ASL 4c:LSF

The examples in (5) illustrate two occurrences of MR taken from, respectively, the LIS (5a), and ASL (5b) narratives analysed for the present study. In 5a, the TP and TS structure produced allow the signer to anaphorically refer simultaneously to a 'child holding a dog in his arm' and to 'the dog licking the child on his cheek'. In 5b, the same type of structures allows the signer to represent 'a dog' with 'a jar' around his neck.

(5) 5a: LIS 5b: ASL Note that TS structures such as those illustrated in (4) are also examples of MR.

Evidence from previous studies and questions investigated in the present study

Previous studies conducted on LSF have provided clear evidence on the extensive use of HIS in LSF texts of different genres. This has been shown in [START_REF] Cuxac | Fonctions et structures de l'iconicité des langues des signes[END_REF][START_REF] Cuxac | La Langue des Signes Française (LSF). Les voies de l'iconicité[END_REF] analyses of large texts produced by a small number of LSF signers, and in more recent work conducted by [START_REF] Sallandre | Les Unités du Discours en Langue des Signes Française. Tentative de Catégorisation dans le Cadre d'une Grammaire de l'Iconicité[END_REF] on a large corpus of short narratives and 'prescriptive' (cooking recipes) texts produced by 19 signers. Sallandre's results also highlight important differences with respect to discourse genres:

HIS are much more frequent in narrative (on average 70%) compared to prescriptive texts (30% on average). Disregarding terminological differences among authors, similar indications on the widespread use of HIS in different genres of signed discourse can be drawn from analyses and observations reported for LIS (Pizzuto, 2004/to appear;[START_REF] Pizzuto | Manual and Non-Manual Morphology in Italian Sign-Language: Grammatical Constraints and Discourse Processes[END_REF][START_REF] Russo | Iconicity and productivity in sign language discourse: an analysis of three LIS discourse registers[END_REF][START_REF] Pizzuto | Formazione di parole visivo-gestuali e classi grammaticali[END_REF][START_REF] Russo | Italian Sign Language (LIS) poetry: iconic properties and structural regularities[END_REF][START_REF] Wilkinson | Deaf and hearing signers with different signing experience; preliminary data from analyses of narrative texts ("Frog Story[END_REF], for BSL [START_REF] Brennan | Encoding and capturing productive morphology, Sign Language & Linguistics-Special Issue, Sign transcription and database storage of sign information[END_REF], ASL (Emmorey & Reilly 1998;Emmorey, 2003), DSL (Engberg-Pedersen, 1993;2003).

No study that we are aware of, however, has explicitly addressed the question we aimed to clarify with the present, cross-linguistic study:

1. How frequently are HIS used for performing deictic-anaphoric reference operations?

2. Are HIS more or less frequently used, for deictic-anaphoric reference purposes, compared with 'standard' signs and manual pointings?

3. In performing deictic-anaphoric reference operations via HIS, what is the incidence of MR, i.e. how frequently does the use of HIS allow signers to simultaneously introduce or re-introduce in discourse two (or even more) referents?

Data used for the present study

The data we used for the present study were drawn from more extensive corpora of signed discourse of different genres that have been collected in France, Italy and USA on a fairly large number of native and non native ASL, LIS and LSF signers [START_REF] Wilkinson | Deaf and hearing signers with different signing experience; preliminary data from analyses of narrative texts ("Frog Story[END_REF][START_REF] Sallandre | Les Unités du Discours en Langue des Signes Française. Tentative de Catégorisation dans le Cadre d'une Grammaire de l'Iconicité[END_REF][START_REF] Sallandre | Simultaneity in French Sign Language Discourse[END_REF][START_REF] Pizzuto | Formazione di parole visivo-gestuali e classi grammaticali[END_REF]. In the present work we analyze short narrative texts elicited through two different pictured stories that have been widely employed in much research on both SL and spoken languages. The LIS and ASL narratives were elicited through the same story, "Frog where are you?" [START_REF] Mayer | Frog, where are you?[END_REF]. The LSF narratives were elicited through "The Horse" story [START_REF] Hickmann | Children's discourse: person, space and time across languages[END_REF].

In the book version we used as elicitation material, the 'Frog' story is made of 24 pictures. It tells the adventures of a boy, his dog, a frog. The boy (main protagonist) finds a frog, brings it home, puts it in a jar placed in his bedroom, then goes to sleep with the dog. During the night, while the boy and the dog are sleeping, the frog jumps out of the jar and escapes. The next morning, the boy wakes up and finds out that the frog has disappeared. The boy and the dog then start searching everywhere for the frog.

The 'Horse' story is made of 5 pictures, hence much 'shorter' than the 'Frog' story. It narrates simple actions performed by a horse, a cow and a bird within the space of a lawn divided by a fence. The main protagonist is the horse, who gallops happily over one side of the lawn and is observed by the cow and the bird positioned, respectively, on the other side of the lawn, and on a picket of the dividing fence. At one point the horse jumps over the fence to join the cow on the other side, but in doing so the horse bumps on the fence, and falls on the other side, landing on its back and hurting one of its legs. The cow and the bird then come to help the horse: the bird brings a first-aid kit which is then used by the cow for bandaging the horse's leg.

These pictured stories were presented to all signers by deaf interviewers who are fluent in each of the SL examined, and with whom the signers were well familiar. All signers were allowed to familiarize themselves with the stories, with no time constraints, and then asked to retell the stories from memory.

For the present study we selected from the larger corpora mentioned above, for each SL, the productions of three native signers of comparable ages (young deaf adults, age range: 19-23 years)

and socio-cultural background (middle-class, high school degree, or attending the first years of university). We focused our analysis on text sequences of comparable content (functionally similar episodes involving animate and inanimate referents), and duration in time (approximately 1' of signed productions). The ASL and LIS data consisted of portions of 'Frog Story' narratives corresponding to the sequence going from the beginning of the story through the episode in which the dog falls from the windowsill, then the boy takes the dog in his arms, and the dog licks the boy on his cheek. The LSF data corresponded to complete narrations of the 'Horse Story'.

The reader may wonder why we used portions of the 'Frog Story' for our ASL and LIS data, and a different story, 'The Horse', for our LSF data. Our choice was in part motivated by indications provided by previous work, but also influenced by practical reasons. Research independently conducted on ASL and LIS 'Frog stories' [START_REF] Wilkinson | Deaf and hearing signers with different signing experience; preliminary data from analyses of narrative texts ("Frog Story[END_REF], and on LSF 'Horse stories' [START_REF] Sallandre | Les Unités du Discours en Langue des Signes Française. Tentative de Catégorisation dans le Cadre d'une Grammaire de l'Iconicité[END_REF] indicated the relevance that semantic features such as animacy vs.

inanimacy, and human vs. not-human may have for a clearer understanding of deictic and anaphoric devices in signed narratives. Both the stories we analysed include animate and inanimate referents, but slightly differ with respect to the 'human' vs. 'non-human' feature of their protagonists: the 'Frog' story has a human character (the boy) as the main protagonist, while in the 'Horse' story all characters are animals, hence not-human. This difference between the two stories can thus provide information on the role that the human vs. not-human feature may have (within the category of reference to animates) in the choice of deictic-anaphoric reference devices in narratives.

When we planned the research reported here, we intended to expand our data base in order to perform our analyses on both "Frog " and "Horse" stories produced in the three SL we examined.

However, time and funding constraints did not allow us to pursue this objective. The present comparative study was thus re-designed, and should be intended, as a first exploration of the topic we focus upon. We acknowledge that a more comprehensive analysis will require more data based on the same language elicitation materials across languages.

Data transcription, coding and analysis

The transcription methodology, and the analytic categories we used for coding were agreed upon among all co-authors on the ground of theoretical work and empirical analyses of signed discourse as described in [START_REF] Cuxac | La Langue des Signes Française (LSF). Les voies de l'iconicité[END_REF], [START_REF] Sallandre | Les Unités du Discours en Langue des Signes Française. Tentative de Catégorisation dans le Cadre d'une Grammaire de l'Iconicité[END_REF] Cuxac & Sallandre (2004/to appear), Pizzuto (2004/to appear), [START_REF] Pizzuto | Formazione di parole visivo-gestuali e classi grammaticali[END_REF].

All signed productions were transcribed and coded in a common format on excel files by signers that were fluent in each of the national SL we considered 5 . We used so-called 'glosses' for annotating in, respectively, written English, French and Italian the basic meaning of the linguistic units we identified in the ASL, LSF and LIS narratives 6 . This 'gloss' notation was integrated, in the excel transcripts we produced, with information on the timing of each unit singled out, and on relevant formal and articulatory features of such sign units (e.g. coding each unit as a standard sign or a HIS of the TF, TS or TP type, the presence/absence of spatial dislocation, the hand/s engaged in producing the manual components of the sign units).

All transcripts realized were subsequently exchanged among all co-authors (along with the original data recorded on DVDs) for cross-checking the uniformity of our transcription and coding methodologies.

The analyses focused upon the referential expressions that were used in the text to introduce The first class (hereafter std) included: (1) all content-loaded signs that are most commonly listed in SL dictionaries (e.g. the standard signs for 'frog', 'house', 'jar'); (2) manual pointings used to position referents at marked locations in the signing space.

The second class included all HIS, distinguished in the three major types of TF, TS and TP, as described in section 1.1 above. Note that for the purposes of the present paper, in the description of our findings to be provided below, the TF and TS subtypes of HIS were grouped in a single category (TF/TS).

We distinguished a third type of deictic-anaphoric productions that included 'mixed' (hereafter 'mix') combinations of HIS and std signs (e.g. a TF produced with one hand vehiculated the meaning of 'jar' accompanied by a manual pointing produced with the other hand pointed to mean 'this jar').

In examining the distribution of std signs vs HIS in deictic and anaphoric reference operations we explored possible differences linked to the animate vs. inanimate status of the referents that were symbolized in discourse. Finally, we examined the incidence of MR (as defined and described above -see examples [4] and [5]), computing their proportion in the texts as follows.

We grouped together all occurrences of deictic-anaphoric reference operations produced, and then divided the number of cases in which a MR was realized by the total number of deictic-anaphoric reference operations produced.

on possible solutions, the interested reader is referred to Di [START_REF] Di Renzo | Italian Sign Language: Can we write it and transcribe it with Sign Writing[END_REF], [START_REF] Garcia | Finalités et enjeux linguistiques d'une formalisation graphique de la langue des signes française (LSF)[END_REF], [START_REF] Pizzuto | Representing signed languages in written form: questions that need to be posed[END_REF].

Results: the prominence of HIS as deictic-anaphoric devices in signed narratives

The major results of our study are summarized in 1 shows the number (and relative percentages) of all tokens of deictic and anaphoric reference devices (grouped together) identified in the texts produced by each signer, distinguished in standard signs, HIS, and mixed productions consisting of standard signs and HIS. Looking at the total number of tokens on the left side of Table 1, it can be observed that, although all the signed texts we analyzed were of comparable time length (1'), the 'Horse' stories produced by the LSF signers contained a smaller number of deictic-anaphoric reference tokens (between 46 and 71) compared to the larger number of such tokens found in the 'Frog' story sequences by the LIS and ASL signers (between 103 and 146, i.e. approximately twice as much).

This shows that, not surprisingly, the specific story used, most likely the different 'length' of the stories in terms of number of pictures of which they are made, influences language production, at least from a quantitative standpoint.

Examining the distribution of the different types of deictic-anaphoric devices in the three languages examined, the relative percentages in the right side of Table 1 highlight that across languages HIS are by far the most frequent device used for deictic-anaphoric reference purposes.

They are in fact represented in similar, very high proportions in LIS (75% to 81%), ASL (73% to 79%), and LSF (78% to 89%). In contrast, the category of std signs are represented in markedly smaller proportions (from 11% to a maximum of 25%), while mixed productions constituted an overall negligible proportion, ranging from 0 to 2%.

Figures 1 through 5 below provide a more detailed description of the regularities we identified across languages. Figure 1 focuses on deictic reference to both animate and inanimate referents (grouped in a single category), showing the distribution (relative %) of std signs, HIS and mixed productions. The data in Figure 1 highlight that in all three SL, with only one exception, standard signs were the preferred means for the first (deictic) introduction of animate and inanimate referents in discourse (ranging from 50% to 83%), while HIS were less frequent, albeit still in appreciable proportions (17% to 45%). One signer (LSF-1) did not follow this pattern, and used much more frequently HIS (83%) rather than standard signs. Mixed productions were also represented in the texts of two signers (LIS-3 and LSF-3), in small proportions.

Figure 2 shows the distribution of HIS vs. standard signs in anaphoric reference to animate and inanimate referents. The data evidence strong cross-linguistic similarities: HIS appear to be by far the prevailing means for carrying out anaphoric reference, in proportions ranging from 76% to as much as 95%. With respect to the use of standard signs, it is of interest to note that a very small proportion of anaphoric reference was performed only via manual pointings. These were absent in the production of the LSF signers, and very poorly represented in the texts by the ASL (1% to 3%)

and LIS (5 to 7%) signers. The data in Figure 3a show different patterns for LIS and ASL, on one hand, and LSF on the other hand. In both LIS and ASL, signers' first reference to the three main, animate protagonists of the 'Frog' story is performed exclusively via standard signs (the names for these referents). In contrast, LSF signers' first reference to the three animate referents of the 'Horse story' is done either via standard signs (in one or two over three possible cases, depending upon the signer), or via HIS, and precisely via TP (in the remaining cases). It is of interest to recall that while the 'Frog' story includes a human animate referent (the boy) in addition to two animal referents, the 'Horse' story has all animal animate referent. We cannot exclude that the LSF signers' use of TP structures for deictic reference (in addition to standard signs) was at least in part influenced by this property of the referents they talked about. We also found that all three LSF signers used a TP structure to introduce the 'cow' referent of their story, articulating very similar manual components or 'proforms' within such structures. This suggests an interaction between semantic properties and formational properties of manual signs for the referents that needs to be further investigated.

Figure 3b illustrates the use of standard vs. HIS as deictic devices for inanimate referents. Looking at the figure, it can be seen that the HIS employed in this case belonged to the TF/TS categories. Major crosslinguistic similarities across the three languages can be noted. In all signers but one (LSF-1), inanimate referents are introduced frequently via standard signs (in proportions ranging from 43% to 78%), but HIS are also well represented either by themselves (from 22% to 50%), or also in combinations with pointings (in the 'mixed' category). The use of TF/TS structures is magnified in the production of LSF-1 (89%), suggesting that individual variation also needs to be carefully assessed for a clearer understanding of the topic we are exploring.

Figures 4a and4b focus on anaphoric reference to, respectively, animate and inanimate referents, and clarify the major trends, and cross-linguistic similarities highlighted in Table 1 and Figure 4a shows that in all three SL the re-introduction in discourse of animate referents was performed primarily via HIS, most frequently of the TP type. In the production of 8 out of 9 signers anaphoric TP were represented in proportions ranging from 48% to 93%, while in one signer (ASL-2) TP were in smaller but still remarkable proportion (33%). Almost all signers also used anaphoric TF/TS structures: these were on average in smaller proportions (between 2% and 27%) except in the production of ASL-2 signer, who used anaphoric TF/TS more frequently (39%) than anaphoric TP (33%). The use of standard signs for anaphoric reference was markedly less frequent (e.g.

between 22% and 26 % in the LIS and ASL signers, from 7% to 10% in the LSF signers). The very high proportion of anaphoric TF/TS structures (from 73% to 100%) is in sharp contrast with the markedly more limited use of standard signs. These were absent from the production of three signers (ASL-3, LSF-1 and LSF-3), and ranged from 3% to 27% in the remaining signers. The data in figure 5 show that MR was realized in all three SL, albeit in variable proportions:

The incidence of multiple reference operations

it was markedly more frequent in LIS signers (from 31% to 51%), relatively less frequent in ASL (17% to 31%) and in LSF signers (11% to 23%). Although individual, and also language differences are noted, it seems unquestionable that MR is a relevant phenomenon that deserves to be taken fully into account in analyses and descriptions of signed narratives.

Concluding remarks

Recalling the questions we formulated, the data we have described evidence clear cross-linguistic similarities among the three SL we examined. These data show that HIS are the most frequent device for realizing anaphoric reference in signed discourse, using primarily TP structures for animate referents, and TF/TS structures for inanimate referents. It was of interest to find that HIS can also be employed for the first, deictic introduction of animate referents (via TP, as noted only in LSF signers), and of inanimate referents (via TF/TS structures, as found in variable but appreciable proportions in all three SL).

Our data also show that in all three SL (in variable but again appreciable proportions), HIS allow MR deictic-anaphoric operations, a unique feature of signed discourse that has been highlighted, from different perspectives, in several recent and less recent studies [START_REF] Dudis | Body partitioning and real-space blends[END_REF][START_REF] Pizzuto | Manual and Non-Manual Morphology in Italian Sign-Language: Grammatical Constraints and Discourse Processes[END_REF][START_REF] Russo | Iconicity and productivity in sign language discourse: an analysis of three LIS discourse registers[END_REF][START_REF] Russo | Italian Sign Language (LIS) poetry: iconic properties and structural regularities[END_REF]Vermeerbergen & al, 2007, among others).

The cross-linguistic similarities we identified appear to be linked more to features proper of the visual-gestural modality rather than to a specific language. In fact, beyond individual differences, we found globally similar patterns not only in ASL and LSF, two languages that are known to be historically related, but also in LIS, a language that has no documented links with either ASL or LSF.

More extensive cross-linguistic research is certainly needed before more conclusive statements can be made on the generalizability of the patterns we found. It will be necessary to for LIS, using a different terminology, in Russo's work comparing LIS poetic texts with expository texts [START_REF] Russo | Iconicity and productivity in sign language discourse: an analysis of three LIS discourse registers[END_REF][START_REF] Russo | Italian Sign Language (LIS) poetry: iconic properties and structural regularities[END_REF]. Although these studies, unlike the present one, were not specifically concerned with the deictic-anaphoric functions of HIS vs. standard signs, they clearly indicate that discourse genre is an important variable that needs to be taken into account.

Recalling the theoretical framework outlined in section 1.1, the following can be noted. The evidence we have discussed questions the more or less widely shared view that establishing 'loci' in space is the primary or 'standard' way for performing deictic-reference operations in SL. As noted, in the narratives we analysed, this strategy was never used by the LSF signers, and rather infrequently used by the ASL and LIS signers.

Our data are more consistent with, and support formal models that attribute a key structural role to iconic features in shaping signed discourse at different levels of analyses [START_REF] Cuxac | Esquisse d'une typologie des Langues des Signes[END_REF][START_REF] Cuxac | Fonctions et structures de l'iconicité des langues des signes[END_REF][START_REF] Cuxac | La Langue des Signes Française (LSF). Les voies de l'iconicité[END_REF]Cuxac & Sallandre, 2004/to appear;Pietrandrea & Russo, 2004/to appear;Pizzuto, 2004/to appear;[START_REF] Russo | Iconicity and productivity in sign language discourse: an analysis of three LIS discourse registers[END_REF][START_REF] Russo | Italian Sign Language (LIS) poetry: iconic properties and structural regularities[END_REF][START_REF] Sallandre | Les Unités du Discours en Langue des Signes Française. Tentative de Catégorisation dans le Cadre d'une Grammaire de l'Iconicité[END_REF]2006;[START_REF] Sallandre | Simultaneity in French Sign Language Discourse[END_REF][START_REF] Sallandre | Iconicity in Sign Language: a theoretical and methodological point of view[END_REF]. Insofar as deictic-anaphoric operations are conceived as a universal function of human language for realizing text cohesion, the pervasive use of HIS in such operations is an additional indication of the relevance of iconic properties for a clearer understanding , and description, of SL grammar.

  the gaze is directed away from the interlocutor, and oriented either towards the hands (when articulating TF and TS structures), or in different points in space reproducing the gaze of the entity represented (when articulating TP structures. Example (2) shows a standard signs and a TF, both encoding the same conceptual content: 'tree'. The proform (handshape within the TF) describes the form of the tree.

(

  deictically) and to keep track (anaphorically) of the animate and inanimate referents symbolized in the narratives. We distinguished all referential expressions in two major classes: (a) standard signs (b) HIS.

Figure 1 -

 1 Figure 1-Deictic reference to animate and inanimate referents: distribution (%) of standard signs (std), HIS and mixed productions (mix) in the texts of the LIS, ASL and LSF signers

Figure 2 -

 2 Figure 2 -Anaphoric reference to animate and inanimate referents: distribution (%) of standard signs (std), HIS and mixed productions (mix) in the texts of the LIS, ASL and LSF signers

Figure 3a -

 3a Figure 3a -Deictic reference to animate referents: distribution (%) of standard signs (std), and HIS (TP) in the texts of the LIS, ASL and LSF signers

Figure 3b -

 3b Figure 3b -Deictic reference to inanimate referents: distribution (%) of standard signs (std), HIS (TP, TF/TS), and mixed productions (mix) in the texts of the LIS, ASL and LSF signers

  Figure 2 above.

Figure 4a -

 4a Figure 4a -Anaphoric reference to animate referents: distribution (%) of standard signs (std) and HIS (TP, TF/TS) in the texts of the LIS, ASL and LSF signers

Figure 4b -

 4b Figure 4b -Anaphoric reference to inanimate referents: distribution (%) of standard signs (std), HIS (TF/TS), and mixed productions (mix) in the texts of the LIS, ASL and LSF signers

Figure 5 Figure 5 -

 55 Figure 5 illustrates how frequently the use of HIS allowed signers to produce what we defined 'multiple reference' (MR), i.e. a multilinear organization of information whereby two or even more referents can be simultaneously specified, and/or maintained in time and space in a fashion that appears to be unique of SL (see examples in section 1.1).

  more data on historically unrelated, geographically distant SL, and to examine different genres of signed discourse. Sallandre' (2003) analyses of different types of LSF discourse has already demonstrated that the frequency with which HIS are used is significantly influenced by discourse types. As noted, HIS are much more frequent in LSF narratives than in 'prescriptive/descriptive' texts such as cooking recipes. Comparable findings have been reported

  Table 1 and in Figures 1 through 5 below. In the table as in the Figures individual signers are indicated by their language and distinguished by numbers (e.g. LIS-1, LIS-2 and LIS-3 indicate the three LIS signers). Table

Table 1

 1 Overall distribution (number and relative percentages) of standard signs (STD), HIS, and mixed productions of std and HIS (mix) used as deictic-anaphoric reference devices in the 'Frog story' texts produced by the three LIS and ASL signers and in the 'Horse story' texts produced by the three LSF signers

	Language /		Number of tokens				%
	Signers
		STD	HIS	mix	TOT		std	HIS	mix	TOT
	LIS-1	26	77	0	103	LIS-1	25	75	0	100
	LIS-2	23	96	0	119	LIS-2	19	81	0	100
	LIS-3	27	118	1	146	LIS-3	18	81	1	100
	ASL-1	28	96	3	127	ASL-1	22	76	2	100
	ASL-2	38	105	0	143	ASL-2	27	73	0	100
	ASL-3	26	100	0	126	ASL-3	21	79	0	100
	LSF-1	5	41	0	46	LSF-1	11	89	0	100
	LSF-2	12	42	0	54	LSF-2	22	78	0	100
	LSF-3	8	62	1	71	LSF-3	11	87	1	100

Erin Wilkinson transcribed the ASL data, Paolo Rossini the LIS data, Marie-Anne Sallandre the LSF data

We are keenly aware that a so-called gloss-based notation, albeit still commonly used by practically all sign language researchers, imposes severe limitations to the analysis of signed utterances and discourse, and more appropriate systems for annotating in written form signed productions are sorely needed. For some recent work on this topic, and indications

acknowledge partial financial support from different agencies, institutions, ongoing projects: the Fulbright Mason Perkins Fund (2000-2001), for supporting Erin Wilkinson's early research at the Istituto di Scienze e Tecnologie della Cognizione of the Consiglio Nazionale delle Ricerche in Rome; the Italian and French National Research Councils (CNR-CNRS Project "Language, its formal properties and cognition: what can be learned from signed languages"); the Istituto Statale Sordi di Roma and the "Progetti Felicità" Funds (Italian project "Writing LIS and Sign Writing"); the French Project ACI Cognitique "LS-COLIN" 2000-2002 (CNRS UMR 7023, IRIT, LIMSI).

Signed Languages. Paper presented at the International Conference Theoretical Issues in Sign

Language Research, TISLR 9, Florianopolis, Brazil, December 6-9, 2006. Wilbur, R. B. (1979). American Sign Language and sign systems: Research and applications.

Baltimore: University Park Press.


Fabien ; Durola

Jacques Lux

Jean-Pierre Sauvage

Oliver S Wenger

Bigger, better, faster: Molecular shuttles with sterically non-hindering biisoquinoline chelates

Keywords: molecular shuttles, copper, biisoquinoline, chelates

published or not. The documents may come     Bigger, better, faster: Molecular shuttles with sterically non-hindering biisoquinoline chelates

Introduction

The field of molecular machines is vast, and there is a large variety of different ways how mechanically interlocked molecules can be assembled and set into motion. [1][2][3][4][5][6][7][8][START_REF] Balzani | Molecular Devices and Machines -Concepts and perspectives for the Nanoworld[END_REF] One possibility, applied since many years in the Strasbourg group, involves the use of coordination chemistry. [START_REF] Livoreil | [END_REF][11][12][13][14][15] Indeed, transition metals are particularly well suited for gathering various organic building blocks and disposing them in a given spatial arrangement. Thanks to its well-defined tetrahedral coordination geometry, copper(I) has been particularly useful for the construction of many catenanes and rotaxanes. [START_REF] Schill | Catenanes, Rotaxanes and Knots[END_REF][START_REF] Dietrich-Buchecker | [END_REF][18][19][START_REF] Sauvage | Molecular Catenanes, Rotaxanes and Knots[END_REF] A key ingredient on this route to multicomponent assemblies are bidentate chelators that can be incorporated into a molecular ring in endocyclic fashion. This is the case for example for 2,9-disubstituted 1,10-phenanthroline or 6,6'disubstituted 2,2'-bipyridine. As seen from Scheme 1, the endocyclic coordination mode can only be enforced with these two particular substitution patterns. Any substitution other than in α-position to the nitrogen atoms will either lead to a mixture of endocyclic and exocyclic species or to preferred exocyclic coordination. The 2,9-diphenyl-1,10-phenanthroline (dpp) fragment has played a particularly prominent role due to its extended rigid backbone. This chelator forms very stable [Cu(dpp) 2 ] + complexes with endocyclic coordination, and mechanically interlocked molecules can be obtained through macrocyclisation via flexible polyethylene glycol chains attached to the dpp-phenyls and subsequent removal of the metal. [START_REF] Dietrich-Buchecker | [END_REF]22] While this approach to obtaining catenanes and rotaxanes has been very successful, it also has its limitations.

Firstly, steric constraints impede the formation of complexes in which three dpp fragments gather around a single octahedral metal center: The dpp ligand is simply too small for this purpose. Secondly, molecular shuttles that involve the [Cu(dpp) 2 ] + fragment exhibit rather slow shuttling kinetics which also has to do with the fact that the dpp ligands are sterically demanding. [13] They shield the copper center too well from the solvent, and this decelerates ligand exchange reactions very significantly. Hence the overall shuttling process, which presumably requires the exchange of one dpp ligand by solvent molecules, is becoming slow.

These two important drawbacks of the dpp ligands have provided the motivation for the search of a new family of bidentate chelators that could be included in macrocycles in an endocyclic but sterically nonhindering fashion. Our search has been successful with the synthesis of 8,8'-disubstituted 3,3'biisoquinolines. [23,24] Here, we review the coordination chemistry of these new ligands on a few selected examples (section 2), and we report on molecular shuttles that are based on the coordination chemistry of these ligands (section 3). As seen from Scheme 2, there are certain analogies between the long-known dpp-ligands and the newly synthesized 8,8'-disubstituted 3,3'-biisoquinolines, but there are also some very important differences.

Although both types of ligands are bidentate chelators, the biisoquinolines have no substituents at the α-positions to the chelating nitrogen atoms which is in contrast to the dpp molecules. Common to both ligands is the crescent shape, thereby allowing incorporation of each of these ligands in a ring with an endocyclic coordination site, but the 8,8'-diphenyl substituted 3,3'-biisoquinoline fragment (dpbiiq) offers a much more open coordination site than the dpp ligand: The distance between the phenyl rings attached to the 3,3'-biisoquinoline backbone is roughly 11 Å, whereas for the 1,10-phenanthroline backbone it is only about 7 Å. [25] Indeed, in the biisoquinoline ligand, the coordinated metal center will be rather remote from the phenyl-rings used to ensure the endocyclic coordination mode. The synthesis of the 8,8'-disubstituted biisoquinolines proceeds over several synthetic steps, yet it is possible to produce gram-scale quantities of a variety of molecules of this type in a reasonable amount of time. [24] We explored the synthesis of 3,3'-biisoquinolines that bear phenyl or biphenyl substituents at the 8 and 8' positions, but encountered serious solubility problems with the latter. A key finding is that with these new ligands it is possible to form homoleptic complexes in which three such ligands are coordinated to one single metal center. [26] This is illustrated by Figure 1 which shows the chemical formulas and X-ray crystal structures of a ruthenium(II) complex with three 8,8'-dianisyl-3,3'-biisoquinoline ligands (left) and an iron(II) complex with three 8,8'-diphenylanisyl-3,3'-biisoquinoline ligands (right). ] 2+ . Right: X-ray crystal structures of these complexes. [26] The successful synthesis of the complexes from Figure 1 confirms the initial hypothesis formulated at the outset of this research: Cleary, the new biisoquinoline ligands are sterically non-hindering despite their endocyclic coordination modes. The three-component entanglements of three crescent-shaped chelates coordinated to a single octahedral metal center result in more or less symmetrical helical pseudo-D 3 structures. The endotopic cleft distances, i. e., the distances between the oxygen atoms attached to two different anisyls on a given 3,3'-biisoquinoline, range from 15.6 to 16.4 Å in the case of the ruthenium complex with the shorter 8,8'-dianisyl-3,3'-biisoquinoline ligand, and from 18.7 to 20.9 Å in the iron(II) complex with the longer 8,8'-diphenylanisyl-3,3'-biisoquinoline ligand. [26,27] These structures are not only aesthetically pleasing, but they also form the basis for multi-component assemblies with new chemical topologies, a branch of research that we have reviewed recently. [28] Here, we intend to focus on the use of the sterically non-hindering ligand family for the construction of new copper-based molecular machines.

Fast-moving molecular shuttles based on copper coordination chemistry and biisoquinoline macrocycles

Molecular shuttles [29][30][31][32][33][34][35][36][37][38][39][40][41][42][43] constitute a sub-class of molecular machines. Typically, they contain a molecular ring that can glide along an axis on which it has been threaded, whereby the motion can be triggered at will through application of an external stimulus. At least two stations are needed on the molecular axis between which the molecular ring may shuttle back and forth. The approach of the Sauvage group is based on the use of bi-and tri-dentate chelate ligands as stations on the axis, and macrocycles incorporating bidentate ligands as gliding rings, whereby the two components are held together by copper(I/II) ions. [13,[44][45][46] The external stimulus triggering the molecular movement is of electrochemical nature: The change in metal oxidation state induces the shuttling motion. The working principle of such a two-station molecular shuttle is illustrated by Scheme 3. Scheme 3. Working principle of a two-station molecular shuttle comprised of a molecular axis with a bidentate chelate (e. g., a dpp-fragment) and a tridentate ligand (e. g., a terpyridine chelate). The molecular ring is typically a macrocycle incorporating a dpp-fragment.

At the starting point (top left), copper is in its +I oxidation state for which tetrahedral coordination is thermodynamically preferred, hence the Cu(I) ion is coordinated to the two bidentate ligands. Cu(II), by contrast, prefers higher coordination numbers. Therefore, immediately after oxidation (top right), the copper ion finds itself in a thermodynamically unstable coordination environment. The consequence is decoordination of the Cu(II) ion from the bidentate chelate on the molecular axis and translation of the Cu(II)macrocycle moiety to the station offering the terdentate ligand (bottom right). Upon reduction of Cu(II), an unstable five-coordinate Cu(I) complex will be formed temporarily (bottom left), and this induces the backshuttling of the metal-macrocycle entity to the starting point.

These molecular shuttles are usually true rotaxanes, i. e., there are bulky groups attached to the two ends of the molecular axis, preventing the macrocycle from de-threading. Hence, the shuttling process is usually highly reversible.

Scheme 4 shows a specific example of such a molecular two-station shuttle that was prepared and studied by the Strasbourg group. [13] In this compound, the molecular axis is flexible, which makes it difficult to have a clear view of the geometry and the exact distance between the two stations of the shuttle. Moreover, in the thermodynamically stable tetrahedral copper(I) complex, the metal center is almost completely isolated from the chemical environment: The two sterically demanding 2,9-diphenyl-1,10-phenanthroline (dpp) ligands shield the copper from the solvent. Thus, upon oxidation to Cu(II), the resulting thermodynamically unstable [Cu(dpp) 2 ] 2+ complex stays kinetically inert, because the transient formation of a mobile solvent complex of Cu(II) is made difficult. As a consequence, the rearrangement of the thermodynamically unstable fourcoordinate species Cu (4) (II) to the five-coordinate species Cu (5) (II), i. e. the gliding motion of the copper center plus macrocycle along the molecular axis, takes place only on a minute to hour timescale. [13] The same is true for the reverse process: When Cu(II) is reduced while being coordinated to the terpyridine station and the macrocyclic dpp-ligand, the resulting five-coordinate species Cu (5) (I) is also kinetically inert, and the thermodynamically preferred four-coordinate species Cu (4) (I) is formed equally slowly. In other words, both the forward and backward shuttling kinetics are very slow. As shown recently for "pirouetting" copper-complexed rotaxanes, decreasing the steric congestion around the copper coordination center has a strong effect on the rearrangement rates of the complexes. [47] Therefore we reasoned that by using a macrocycle that incorporates the sterically non-hindering dpbiiq fragment 3 instead of the dpp-fragment 1, the shuttling kinetics of our molecular machines might be improved. Toward this end, we have prepared macrocycle 8 (Scheme 5) which is considerably bigger than the dpp-based macrocycle 9 which was used in the molecular shuttle from Scheme 4. The new macrocycle 8 is 39membered and provides an inner cavity that is about 11 Å wide, whereas the the dpp-based macrocycle 9 is only 30-membered with an inner cavity of roughly 7 Å width. We have used the sterically less congesting macrocycle 8 as the mobile part in a new molecular shuttle (Scheme 6). In this rotaxane, the molecular axis differs from the previously used axis (Scheme 4) in several respects. The most important difference is that the phenanthroline and the terpyridine stations are now connected via a rigid p-phenylene spacer. This makes the new axis significantly less flexible than that of the rotaxane from Scheme 4. Scheme 6. A copper-based molecular shuttle with a rigid axis and a sterically non-hindering macrocycle.

The electrochemically triggered translation of the copper-complexed ring between the dpp and the terpy stations of the molecular axis was investigated using cyclic voltammetry, by analogy with previously described copper-containing bistable catenanes and rotaxanes [START_REF] Livoreil | [END_REF]11,13] . Through variation of the potential scan rate, it is possible to obtain kinetic information on the gliding motion of the macrocycle. [48,49] A few representative cyclic voltammograms (CVs) are shown in Figure 2. [45] for experimental details. Potentials are reported versus SCE.

At the starting point of our CV experiments, molecular shuttle 10 from Scheme 6 has Cu(I) coordinated to dpp on the axis and dpbiiq on the macrocycle. At all scan rates, we observe only one single wave in the oxidative scan, centered around 0.48 V vs. SCE. This wave corresponds to oxidation of four-coordinate Cu(I). In the reductive sweep at low scan rates (50 mV/s), we observe a wave that is centered around 0.07 V vs. SCE which is due to reduction of Cu(II) in five-coordinate environment. This indicates that by the time the reductive sweep begins, the shuttling motion from the bidentate dpp-station to the terdentate terpystation has already taken place. When the scan rate is increased to 400 mV/s, a second reductive wave becomes observable. This wave is centered around 0.42 V vs. SCE and is attributed to reduction of Cu(II) in four-coordinate environment. This is a clear indication that under these experimental conditions, some of the molecular shuttles did not have sufficient time to undergo the gliding motion that should have followed Cu(I) to Cu(II) conversion in the oxidative sweep. Interestingly, an oxidation wave that could be associated with Cu(I) oxidation in a five-coordinate environment cannot be observed even at a scan rate of 1000 mV/s. This indicates that the gliding motion from the terpy to the dpp station following Cu(II) reduction is significantly faster that the reverse gliding motion that follows Cu(I) oxidation. This finding is in line with previous observations on other molecular machines investigated by the Strasbourg group. [START_REF] Livoreil | [END_REF]13,[50][51][52][53] For comparison, in molecular shuttle 7, the rate constants for the two gliding motions are at least two orders of magnitude lower. It is tempting to attribute this dramatic acceleration fully to the sterically non-hindering nature of the new dpbiiq-based macrocycle, yet it must be noted that shuttles 7 and 10 differ also in the nature of the molecular axis. In shuttle 7, there is a flexible axis with an alkane linker between the two stations, whereas in shuttle 10 there is a rigid axis with a p-phenylene spacer. In order to eliminate any doubts regarding the origin of the improved shuttling kinetics, we have investigated molecular shuttle 11

that is comprised of the same rigid axis as shuttle 10, but with the sterically congesting 30-membered dppbased macrocycle 9 (Scheme 7).

Scheme 7. A molecular shuttle comprised of the same rigid axis as the shuttle from Scheme 6, but with the smaller macrocycle 9 instead of the sterically non-hindering macrocycle 8.

The difference in gliding kinetics between shuttles 10 and 11 is remarkable. As discussed above, in the shuttle with the biisoquinoline-macrocycle, gliding from the phenanthroline station to the terpyridine station following Cu(I) oxidation occurs within less than a second. By contrast, after Cu(I) oxidation of rotaxane 11, the thermodynamically unstable four-coordinate species is stable for several hours. Thus, it is obvious that there exists a pronounced kinetic biisoquinoline effect.

The endocyclic but sterically non-protecting nor hindering nature of dpbiiq is the key to this spectacular improvement. Besides this non hindering character, another important structural difference between dpp and the biisoquinoline ligand is the less rigid nature of the latter. Whereas dpp contains a rigid backbone, the With these encouraging results at hand, it became realistic to envision molecular shuttles in which the translational motion occurs over a significantly longer distance [54][55] than in the prior systems. This vision included the use of a molecular axis with three instead of only two stations: The end stations should be comprised of the bidentate 1,10-phenanthroline ligand (dpp) to host preferably Cu(I) and the terdentate terpyridine chelate to host preferably Cu(II) as in the shuttles from Schemes 6 and 7. The hypothesis was that a 2,2'-bipyridine ligand could serve as an intermediate station that can facilitate the shuttling motion between the two end points. With this ultimate goal in mind, it seemed reasonable to explore in a first step the coordination chemistry and electrochemical behavior of a two-station shuttle containing only a 1,10phenanthroline (dpp) and a bipyridine (bipy) station. The resulting system, rotaxane 12, [56] is shown in Scheme 8. By contrast to the molecular shuttles previously investigated by the Strasbourg group, [13,[44][45][46] this shuttle contains exclusively bidentate ligands and no terdentate chelates at all. Thus, even Cu(II) will only achieve a fourfold coordination as far as the nitrogen atoms of the chelates are concerned. However, it should be kept in mind that when the coordination sphere around these chelates is sterically not too demanding, there may be solvent molecules or anions that can coordinate to Cu(II), thereby satisfying its demand for higher coordination numbers. Indeed, the steric properties of the phenanthroline and bipyridine stations are vastly different: The former is highly shielding and prevents the copper center from interacting with the chemical environment, uptake of solvent molecules or anions as additional ligands is very difficult in this coordination site. The bipyridine station, on the other hand, is sterically much less demanding. Thus, it can be expected that additional ligation of solvent molecules or counterions will stabilize Cu(II) when coordinated to the The relative thermodynamic stabilities between the Cu(I) and Cu(II) complexes formed in the molecular shuttle define the driving force for the shuttling motion. Evidently, the thermodynamic stability of Cu(II) in a bipyridine-biisoquinoline coordination environment (as the case for shuttle 12 of Scheme 8) will differ from the thermodynamic stability of Cu(II) in a terpyridine-biisoquinoline coordination (as the case for shuttle 10 of Scheme 6). As a consequence, the driving force for the ring-translation in the phenanthrolinebipyridine shuttle will be different from that in the phenanthroline-terpyridine shuttle. This driving force can be estimated from the redox potentials of the various copper complexes. For shuttle 10, the relevant data can be extracted from the cyclic voltammograms in Figure 2: The [Cu(dpbiiq)(dpp)] + complex is oxidized at 0.46 V vs. SCE, the [Cu(dpbiiq)(terpy)] 2+ species is reduced at 0.07 V vs. SCE. Hence, the driving force ∆G for ring translation in the phenanthroline-terpyridine shuttle is roughly 0.39 eV. In order to estimate the driving force for the phenanthroline-bipyridine shuttle, the model complexes shown in Scheme 9 were synthesized and investigated electrochemically. With this basic knowledge at hand, we undertook an electrochemical study of the new phenanthrolinebipyridine shuttle, [56] similar to that discussed above for the phenanthroline-terpyridine system, using different potential scan rates to obtain kinetic information on the shuttling motion. Representative cyclic voltammetry data resulting from this work are shown in Figure 3. Through comparison of the three data sets in Figure 3, the assignment of the different redox waves observed for shuttle 12 becomes straightforward: The oxidative wave of shuttle 12 around 0.42 V vs. SCE is also observed in the voltammogram of [Cu(dpbiiq)(dpp)] + reference complex 13 and therefore can be assigned to Cu(I) oxidation with the macrocyle located at the 1,10-phenanthroline station. In the voltammogram of complex 13, there is an additional oxidation wave around 0.65 V vs. SCE that we attribute to a [Cu(dpp) 2 ] + impurity that is formed under the experimental conditions used for the synthesis of 13. This seems to be inevitable due to the high thermodynamic stability of the [Cu(dpp) 2 ] + complex. The reductive sweep of shuttle 12 exhibits a wave around 0.18 V which coincides with the reduction wave observed in the voltammogram of [Cu(dpbiiq)(bipy)] 2+/+ reference complex 14 rather than with the reduction wave observed for [Cu(dpbiiq)(dpp)] 2+/+ reference complex 13. This is a clear indication that at the potential scan rate used for the experiments in Figure 3 (100 mV/s), by the time the oxidative sweep is finished and the reductive sweep begins, the copper-macrocycle entity has already travelled from its initial position at the phenanthroline station to the bipyridine station. By analogy to our prior investigations, we varied the potential scan rates to obtain information on the shuttling kinetics. Figure 4 shows a series of As the scan rate is increased from 200 mV/s to 800 mV/s and finally 1600 mV/s, there are no significant alterations in the oxidative sweep, but the reductive scan gradually changes. At 200 mV/s one still observes the reduction wave associated with the [Cu(dpbiiq)(bipy)] 2+/+ complex, i. e., reduction of Cu(II) at the bipyridine station. At 1600 mV/s on the other hand, the reduction occurs at a significantly higher potential and coincides with the reduction wave observed for the [Cu(dpbiiq)(dpp)] 2+/+ complex 13 from Figure 3.

This shows that at this scan rate, Cu(II) is reduced while located at the phenanthroline station. Under these experimental conditions, the traveling motion from the phenanthroline to the bipyridine station cannot keep up with the high potential scan rate: Reduction of Cu(II) occurs while the metal is still in its initial coordination environment. Remarkable is the complete absence of an oxidative wave in the voltammogram of shuttle 12 that could be attributed to Cu(I) oxidation in a biisoquinoline-bipyridine coordination, even at the highest scan rate of 1600 mV/s. This indicates that molecular movement originating from the unstable [Cu(dpbiiq)(bipy)] + complex is much faster than the shuttling motion originating from thermodynamically unstable [Cu(dpbiiq)(dpp)] 2+ complex. From our scan-rate dependent cyclic voltammetry experiments, a rate 14 constant of 0.8 s -1 can be extracted for the shuttling motion of macrocycle 8 from the dpp station to the bipy ligand, whereas for the reverse motion a lower limit of 50 s -1 is estimated. The magnitude of these rate constants is comparable to that for the dpp-terpy shuttle from Scheme 6, indicating that the lower thermodynamic driving force in the dpp-bipy shuttle from Scheme 8 is not a crucial factor as far as the shuttling kinetics are concerned.

With the dpp-terpy and dpp-bipy two-station shuttles completely characterized and identified as fully operational systems, the construction of a three-station shuttle comprised of one dpp, one bipy and a terpy station became a realistic goal. We have therefore prepared rotaxane 16 as shown in Scheme 10. [29] Scheme 10. Three-station rotaxane 16 containing dpp, bipy and terpy stations on the molecular axis and dpbiiq-based macrocycle 8. The subscripts indicate the coordination numbers of the copper center.

The estimated distance between the two terminal coordination sites on the three-station molecular axis is 23 Å, which is considerably larger than in all previously investigated molecular shuttles of this type. Depicted in Scheme 10 are the thermodynamically stable forms for Cu(I) and Cu(II). From the studies of the twostation shuttles described above, the following order of thermodynamic stabilities for the individual copper From this comparison, assignment of the redox waves observed for the three-station shuttle 16 is straightforward: The oxidative wave observed for 16 at 0.38 V vs. SCE coincides with the wave at 0.37 V vs. SCE for two-station shuttle 10 and previously assigned to Cu(I) oxidation in four-coordinate dpbiiq-dpp environment. This assignment is in line with the oxidation potential of 0.38 V vs. SCE determined for [Cu(dpbiiq)(dpp)] + reference complex 13. In the reductive sweep of the voltammogram of three-station shuttle 16, there is only one clear reduction wave, and it is located at -0.02 V vs. SCE. This coincides with the reduction wave observed for [Cu(dpbiiq)(terpy)] 2+ reference complex 15, and consequently can be assigned to reduction of Cu(II) in five-coordinate dpbiiq-terpy environment. The overall appearance of the voltammogram of three-station shuttle 16 is thus very similar to that of two-station dpp-terpy shuttle 10: The same oxidation and reduction waves are observed, and there are no additional waves in the voltammogram of 16 that would be indicative of bipyridine-ligated copper. In other words, there is no electrochemical evidence for copper being coordinated to the intermediate bipy station. This observation suggests that translation away from the bipy ligand is fast in both directions: For Cu(II), bipy-to-terpy translation must be faster than dpp-to-bipy translation, and for Cu(I), bipy-to-dpp translation must be faster than terpy-to-bipy translation. Under these circumstances, the stationary concentration of the intermediate bipy-complex always stays low and its electrochemical signal cannot be detected. Indeed, from our experiments on the three-station shuttle it is not clear whether the bipy ligand behaves as a real station that ligates to copper for a certain residence time.

Anyhow, scan-rate dependent cyclic voltammetry experiments similar to those presented in Figures 2 and4 allow us to estimate a rate constant of 0.4 s -1 for the shuttling motion from the dpp site to the terpy ligand upon Cu(I) oxidation, and the reverse process following Cu(II) reduction occurs with k ≥ 50 s -1 .

Conclusions

The use of a sterically non-hindering biisoquinoline chelate allows the construction of molecular shuttles that exhibit greatly improved shuttling kinetics when compared to analogous systems that are based on sterically demanding macrocycles. When threaded on exactly the same molecular axis, a biisoquinoline-

2 Scheme 1 .

 21 Scheme 1. 2,9-substitution of 1,10-phenanthroline and 6,6'-substitution of 2,2'-bipyridine results in macrocycles with endocyclic coordination. Substitution at other positions is expected to lead to both endoand exocyclic macrocycles.

2 .

 2 Coordination chemistry of 8,8'-disubstituted 3,3'-biisoquinolines

Scheme 2 .

 2 Scheme 2. Endocyclic ligands based on 2,9-diphenyl-1,10-phenanthroline (ddp) and 8,8'-diphenyl-3,3'biisoquinoline (dpbiiq).

Figure 1 .

 1 Figure 1. Left: Chemical structures of [Ru(8,8'-dianisyl-3,3'-biisoquinoline) 3 ] 2+ and [Fe(8,8'diphenylanisyl-biisoquinoline) 3 ] 2+. Right: X-ray crystal structures of these complexes.[26]

Scheme 4 .

 4 Scheme 4. Two-station molecular shuttle with a relatively flexible molecular axis containing a dpp-station and a terpyridine-station and a 30-membered macrocycle incorporating a dpp chelate.

7 Scheme 5 .

 75 Scheme 5. A 39-membered macrocycle with the dpbiiq ligand motif and a 30-membered macrocycle with the dpp fragment.

Figure 2 .

 2 Figure2. Cyclic voltammograms obtained on the molecular shuttle from Scheme 6 at three different potential scan rates. See reference[45] for experimental details. Potentials are reported versus SCE.

  From these cyclic voltammetry experiments, we extract the following rate constants for the back-and-forth motion of macrocycle 8 in molecular shuttle 10: 10 (4)+ -e - ---> 10 (4)

  to rotate around its C 3 -C 3' bond, and this may facilitate de-coordination from a metal center through stepwise de-complexation of one nitrogen donor atom after the other.

Scheme 8 .

 8 Scheme 8. A phenanthroline-bipyridine two-station shuttle in its two different forms 12 dpp + and 12 bipy 2+ ; the subscripts dpp and bipy indicate the position of the mobile ring (macrocycle 8) on the molecular axis.

  thereby making this the thermodynamically preferred station for the metal in its divalent oxidation state.

Scheme 9 .

 9 Scheme 9. Reference complexes for electrochemical investigations.

12 Figure 3 .

 123 Figure 3. Cyclic voltammograms of shuttle 12 and the reference complexes 13 and 14 recorded on a Pt working electrode in CH 2 Cl 2 /CH 3 CN (1:9) with 0.1 M Bu 4 NPF 6 at 100mV/s. The reversible redox couple at 0.9 V vs SCE is due Os(tterpy) 2 2+ (tterpy = 4'-p-tolyl-2,2',6',2"-terpyridine) which was used as an internal reference in this work.

Figure 4 .

 4 Figure 4. Cyclic voltammograms of rotaxane 12 recorded at various potential scan rates in CH 2 Cl 2 /CH 3 CN (1:9) with 0.1 M Bu 4 NPF 6 .

  Scheme 11. Operating principle of the molecular three-station shuttle 16 from Scheme 10.

Figure 5 .

 5 Figure 5. Comparison of the cyclic voltammograms for three-station shuttle 16, [Cu(dpbiiq)(dpp)] + reference complex 13, [Cu(dpbiiq)(bipy)] + reference complex 14, [Cu(dpbiiq)(terpy)] 2+ reference complex 15, and two-station dpp-terpy shuttle 10. The measurements were performed in CH 2 Cl 2 /CH 3 CN (1:9) with 0.1 M Bu 4 NPF 6 using a Pt working electrode and a scan rate of 100 mV/s. The reversible wave at 0.9 V vs. SCE is due to Os(tterpy) 2 2+ (tterpy = 4'-p-tolyl-2,2',6',2"-terpyridine) which was used as an internal reference.

based 39 -A 39 -A

 3939 membered macrocycle moves several orders of magnitude more rapidly than a 30-membered phenanthroline-based macrocycle. When threaded onto a rigid molecular axis in which the overall distance between the two terminal stations is increased from roughly 11 Å to about 23 Å, the shuttling kinetics for the biisoquinoline-based macrocycle do not decrease significantly. While it is likely that the presence of a third station of intermediate thermodynamic stability facilitates shuttling over the 23 Å distance, there is no doubt that the key to these results is the biisoquinoline core of the mobile ring. With respect to the previously investigated phenanthroline-based systems it may thus be stated that the new biisoquinoline-macrocycles are only bigger, they also lead to faster shuttling kinetics in rotaxane-type molecular machines. Thus, bigger rings give rise to better performance due to faster molecular movements, and sterically non-hindering biisoquinoline chelates are truly bigger, better and faster. structures of [Ru(8,8'-dianisyl-3,3'-biisoquinoline)3]2+ and [Fe(8,8'-diphenylanisylbiisoquinoline)3]2+. Right: X-ray crystal structures of these complexes. [26] 95x75mm (450 x 450 DPI) Page 20 of 35 URL: http:/mc.manuscriptcentral.com/tandf/gsch Email: suprachem@mail.cm.Cyclic voltammograms obtained on the molecular shuttle from Scheme 6 at three different potential scan rates. See reference [45] for experimental details. Potentials are reported versus SCE. 94x109mm (350 x 350 DPI) Page 21 of 35 URL: http:/mc.manuscriptcentral.com/tandf/gsch Email: suprachem@mail.cm.Cyclic voltammograms of shuttle 12 and the reference complexes 13 and 14 recorded on a Pt working electrode in CH2Cl2/CH3CN (1:9) with 0.1 M Bu4NPF6 at 100mV/s. The reversible redox couple at 0.9 V vs SCE is due Os(tterpy)22+ (tterpy = 4'-p-tolyl-2,2',6',2"-terpyridine) which was used as an internal reference in this work. 154x199mm (300 x 300 DPI) Page 22 of 35 URL: http:/mc.manuscriptcentral.com/tandf/gsch Email: suprachem@mail.cm.Cyclic voltammograms of rotaxane 12 recorded at various potential scan rates in CH2Cl2/CH3CN (1:9) with 0.1 M Bu4NPF6. 159x175mm (300 x 300 DPI) Page 23 of 35 URL: http:/mc.manuscriptcentral.com/tandf/gsch Email: suprachem@mail.cm.Comparison of the cyclic voltammograms for three-station shuttle 16, [Cu(dpbiiq)(dpp)]+ reference complex 13, [Cu(dpbiiq)(bipy)]+ reference complex 14, [Cu(dpbiiq)(terpy)]2+ reference complex 15, and two-station dpp-terpy shuttle 10. The measurements were performed in CH2Cl2/CH3CN (1:9) with 0.1 M Bu4NPF6 using a Pt working electrode and a scan rate of 100 mV/s. The reversible wave at 0.9 V vs. SCE is due to Os(tterpy)22+ (tterpy = 4'-p-tolyl-2,2',6',2"-terpyridine) which was used as an internal reference. 160x227mm (300 x 300 DPI) Page 24 of 35 URL: http:/mc.manuscriptcentral.com/tandf/gsch Email: suprachem@mail.cm.substitution of 1,10-phenanthroline and 6,6'-substitution of 2,2'-bipyridine results in macrocycles with endocyclic coordination. Substitution at other positions is expected to lead to both endo-and exocyclic macrocycles. 89x57mm (400 x 400 DPI) Page 25 of 35 URL: http:/mc.manuscriptcentral.com/tandf/gsch Email: suprachem@mail.cm.Endocyclic ligands based on 2,9-diphenyl-1,10-phenanthroline (ddp) and 8,8'-diphenyl-3,3'biisoquinoline (dpbiiq). 82x41mm (450 x 450 DPI) Page 26 of 35 URL: http:/mc.manuscriptcentral.com/tandf/gsch Email: suprachem@mail.cm.utexas.Working principle of a two-station molecular shuttle comprised of a molecular axis with a bidentate chelate (e. g., a dpp-fragment) and a tridentate ligand (e. g., a terpyridine chelate). The molecular ring is typically a macrocycle incorporating a dpp-fragment. 139x52mm (450 x 450 DPI) Page 27 of 35 URL: http:/mc.manuscriptcentral.com/tandf/gsch Email: suprachem@mail.cm.Two-station molecular shuttle with a relatively flexible molecular axis containing a dpp-station and a terpyridine-station and a 30-membered macrocycle incorporating a dpp chelate. 89x54mm (450 x 450 DPI) Page 28 of 35 URL: http:/mc.manuscriptcentral.com/tandf/gsch Email: suprachem@mail.cm.membered macrocycle with the dpbiiq ligand motif and a 30-membered macrocycle with the dpp fragment. 85x51mm (400 x 400 DPI) Page 29 of 35 URL: http:/mc.manuscriptcentral.com/tandf/gsch Email: suprachem@mail.cm.utexas.based molecular shuttle with a rigid axis and a sterically non-hindering macrocycle. 89x76mm (400 x 400 DPI) Page 30 of 35 URL: http:/mc.manuscriptcentral.com/tandf/gsch Email: suprachem@mail.cm.molecular shuttle comprised of the same rigid axis as the shuttle from Scheme 6, but with the smaller macrocycle 9 instead of the sterically non-hindering macrocycle 8. 89x35mm (400 x 400 DPI) Page 31 of 35 URL: http:/mc.manuscriptcentral.com/tandf/gsch Email: suprachem@mail.cm.bipyridine two-station shuttle in its two different forms 12dpp+ and 12bipy2+; the subscripts dpp and bipy indicate the position of the mobile ring (macrocycle 8) on the molecular axis. 333x111mm (300 x 300 DPI) Page 32 of 35 URL: http:/mc.manuscriptcentral.com/tandf/gsch Email: suprachem@mail.cm.utexas.Three-station rotaxane 16 containing dpp, bipy and terpy stations on the molecular axis and dpbiiqbased macrocycle 8. The subscripts indicate the coordination numbers of the copper center. 201x150mm (300 x 300 DPI) Page 34 of 35 URL: http:/mc.manuscriptcentral.com/tandf/gsch Email: suprachem@mail.cm.Operating principle of the molecular three-station shuttle 16 from Scheme 10. 193x127mm (200 x 200 DPI) Page 35 of 35 URL: http:/mc.manuscriptcentral.com/tandf/gsch Email: suprachem@mail.cm.utexas.edu Supramolecular Chemistry

  3

URL: http:/mc.manuscriptcentral.com/tandf/gsch Email: suprachem@mail.cm.utexas.edu Supramolecular Chemistry

Acknowledgments

We thank all the skilful and motivated researchers who contributed to this work, namely David Hanss, Alexander I. Prikhod´ko, and Pirmin Roesel. Financial support from the Région Alsace (F. D. and J. L.), the European Commission, and the Swiss National Science Foundation (O. S. W.) is acknowledged. We thank Kari Rissanen and his group for X-ray crystallographic work.