Camila Leandro

Pierre Jay-Robert

Perceptions and representations of animal diversity: Where did the insects go?

Insects are everywhere: they represent 73% of the total described fauna, and, being linked to every ecosystem function, they play key roles in biodiversity resilience. However, are we humans aware of this? Through a study conducted on French students in Environmental and Human Sciences, we designed a free-associations test-based game to elucidate whether Insects were a part of animal diversity representations and which Insects were indeed in students' minds. We also looked for perceived values and related knowledge among taxa in order to examine those results with regard to students' socio-demographic characteristics. Besides a known overall negative perception of invertebrates, we found that this perception was correlated to the "human environment" of the person beyond the "exposure to nature" theory: being surrounded by persons actively involved in nature con-servation increases positive perception of Insecta. Moreover, invertebrates were less seen as a part of ecosystems than vertebrates; this implies a lack of a holistic vision of diversity, which might be the key to improving insect understanding and conservation. Departing from the depiction of insects from a specific group of participants, we propose a generic framework to enhance awareness for insect conservation and recommendations to improve education initiatives. These baselines could significantly help future conservation strategies as they address the perception challenge of insects.

Introduction

Insects represent 73% of the total described fauna (IUCN, 2014). Their great diversity and numbers give them a key role in ecosystem functioning [START_REF] Wilson | The little things that run the world (the importance and conservation of invertebrates)[END_REF][START_REF] Huis Van | The Global Impact of Insects[END_REF] which enhances the need to conserve these taxa [START_REF] Leather | Insect conservation: finding the way forward[END_REF]. Moreover, insects are de-clining worldwide [START_REF] Dunn | Modern insect extinctions, the neglected majority[END_REF][START_REF] Hallmann | More than 75 percent decline over 27 years in total flying insect biomass in protected areas[END_REF], which alter the ecosystem services they provide for human well-being [START_REF] Losey | The economic value of ecological services provided by insects[END_REF], and this decline does not seem to be halted by the current conservation policy based on the protection of strictly delimited areas [START_REF] Hallmann | More than 75 percent decline over 27 years in total flying insect biomass in protected areas[END_REF]. Less charismatic than vertebrates [START_REF] Kellert | Values and perception of invertebrates[END_REF][START_REF] Lorimer | Nonhuman charisma[END_REF], poorly known and more difficult to survey [START_REF] Leather | Insect conservation: finding the way forward[END_REF][START_REF] Cardoso | The seven impediments in in-vertebrate conservation and how to overcome them[END_REF], insects lack pro-tection measures, conservation strategies and, last but not least, peo-ple's concern, valuation and conservation support [START_REF] Samways | Future-proofing insect diversity[END_REF][START_REF] Donaldson | Taxonomic bias and international biodiversity conservation research[END_REF][START_REF] Leandro | Bias and perspectives in insect con-servation: a European scale analysis[END_REF]. [START_REF] Hochkirch | The insect crisis we can't ignore[END_REF] calls for action in the face of this "insect crisis we can't ignore". Two main challenges must be faced: the technical chal-lenge and the perception challenge [START_REF] Samways | Future-proofing insect diversity[END_REF]. While the former is being addressed, until now the latter has been largely neglected [START_REF] Simaika | Insect conservation psychology[END_REF]. Some authors have advocated for the use of flagship species [START_REF] Guiney | Insects as flagship conservation species[END_REF][START_REF] Barua | Selecting flagships for in-vertebrate conservation[END_REF], but such approaches might only enforce charismatic single-species conservation approaches [START_REF] Small | The new Noah's Ark: beautiful and useful species only. Part 1. Biodiversity conservation issues and priorities[END_REF], which might not be the way to efficient insect conservation [START_REF] Leandro | Bias and perspectives in insect con-servation: a European scale analysis[END_REF]. Never-theless, the principle behind this proposal is to leverage conservation through what is explicitly known and what is liked. That is why the study of the psychological side of insect conservation has grown in concern in the late years [START_REF] Samways | Future-proofing insect diversity[END_REF][START_REF] Simaika | Insect conservation psychology[END_REF]. It is important to know which species are recognized and how they are perceived in order to be able to give pertinent solutions for conservation concern, education and action [START_REF] Bennett | Using perceptions as evidence to improve conservation and environmental management[END_REF]. [START_REF] Samways | Insect Diversity Conservation[END_REF] and [START_REF] New | What's in common names: are they really valuable in insect conserva-tion?[END_REF] support the use of common names to enhance people's concern for insects and foster their conservation. The idea is to label with understandable names and shape six-legged forms [START_REF] Duval | The nature of naming in the naming of nature[END_REF][START_REF] New | What's in common names: are they really valuable in insect conserva-tion?[END_REF]. This approach, combined with edu-cational trails, has been used for Odonata species [START_REF] Suh | Development of a dragonfly awareness trail in an African botanical garden[END_REF]. But dragonflies are relatively poorly diversified and the use of such an approach to richer taxa is questionable (e.g. Coleoptera has 60 times more species than Odonata). Moreover, generic names are poly-semous and can be subjective [START_REF] Putnam | The Twin Earth Chronicles Twenty Years of Reflection on Hilary Putnam's "The Meaning of 'Meaning[END_REF][START_REF] Thompson | Nomenclature and classification, principles of[END_REF]; fur-thermore, personal experience soundly modifies the perception of bugs.

Fig. 1. Number of citations of the most cited animal items depending on the environment: A) homes, B) cities, C) agricultural landscapes and D) natural landscapes. Number of citations of the most cited insect items depending on the environments: E) cities, F) natural landscapes. Perception was different between invertebrates and vertebrates (G), but also on the orders cited by the students (H). The bar charts are divided into the proportion of positive perception (green), neutral (grey) or negative (red). The N represents the total number of different cited items by environment (A to F) and the total number of vertebrates or invertebrates cited by participants in each context (G). Icons made by Freepik from www.flaticon.com, CC BY SA license. (For interpretation of the references to colour in this figure legend, the reader is referred to the web version of this article.)

Consequently, what people might think when they use the word "Insect", or other large-diversity englobing terms, might depend on their rational knowledge, personal experiences and on their feelings and factors such as the environment where they grew up and lived [START_REF] Lockwood | The Infested Mind: Why Humans Fear, Loathe, and Love Insects[END_REF]. Nevertheless, names elicit the memory and activate mental images, which can be shared by people [START_REF] Pavio | Images, propositions, and knowledge[END_REF], therefore it is a good entry to study perceptions and representations.

In this study, we investigated the representations, perceptions and knowledge of young adults living in France concerning insects. We specifically focused on students as they form the rising generation, which has to face the Sixth Extinction. Our goals were to get 1) their knowledge, 2) their perception of insects and 3) socio-demographic information that might influence their perceptions and representations. The specificity of their relationship with insects is highlighted by a comparison with their relationship with animals as a whole.

Methods

Definitions

Perception and Representation are results of external and internal factors, related to knowledge, cultural context and personal, or even shared, emotions [START_REF] Zadra | Emotion and perception: the role of affective information[END_REF][START_REF] Wan | Shared knowledge matters: culture as intersubjective representations[END_REF]. [START_REF] Bennett | Using perceptions as evidence to improve conservation and environmental management[END_REF] definition of Perception, "the way an individual observes, understands, interprets, and evaluates a referent object, action, experience, in-dividual, policy, or outcome", as it is a synthesis of established defini-tions with a conservation focus focal, was used. We used [START_REF] Bernoussi | La notion de représentation: de la psychologie générale à la psychologie sociale et la psychologie du développement[END_REF] and Oxford Dictionary definitions to state Representation: a description, an image, a model or other depiction of something (a concept) which is encoded in the mental structure of the descriptor, its memory. As perceptions and representations have key roles in conservation as they shape attitudes towards biodiversity [START_REF] Kellert | Values and perception of invertebrates[END_REF][START_REF] Bennett | Using perceptions as evidence to improve conservation and environmental management[END_REF], in this study we assessed "positive", "neutral" or "negative" valuations and vocabulary related to taxa to go beyond the "good/bad" dichotomy.

Free association method

We used the free association method as a spontaneous and easy-to-implement way to collect participants' representations while using written words as stimuli. This method allows people to elicit reflexive reactions, towards the given stimulus, which are canalized through free writing of word, expressions and even onomatopoeia. It also allows us to access the semantic context in which the mental image of the given stimulus was formed, thus being pertinent method to reveal collective memory and prototypes [START_REF] Dany | Free associations and social representations: some reflections on rank-frequency and importance-frequency methods[END_REF].

Data collection

Our study targeted environmentally aware young adults but without any special skills in natural history. Thus, we excluded working with students in biology or ecology [START_REF] Prévot | The relationship of childhood upbringing and university degree program to environmental identity: experience in nature matters[END_REF] and we choose to work with first year students from the Human and Environmental Sciences Faculty of Paul-Valéry Montpellier 3 University. These students from geography, history or art history chose to attend an optional and purely theoretical introduction to sustainable development taught by one of us (PJR). Tests were given before class in an amphitheater where all students were gathered. Data sampling was conducted in three main phases, all three separated by one week during January 2018. During phase I, we asked students to complete a survey and to answer questions about them-selves, such as experiences with nature, persons potentially influential in their relationship with nature, whether they feared any natural elements and sociodemographical information (Supplementary material A1). Then we addressed the question of which animal and entomological diversity is reported by the students and how is it perceived? To do so, students were asked to complete word association tasks as they are an efficient way to probe subjective conceptions [START_REF] Joffe | Free association in psychology and the grid elaboration method[END_REF]. In phase I, they had to write down, on a sheet of paper with four empty boxes, the first 10 animals they know occurring in four types of environments: their home, the city, an agricultural environment and a natural setting they frequent. Afterwards, participants were asked to put a smiley ( , or ) in front of the items that they cited, representing how they felt about the item. Then we collected all sheets, distributed a new blank one and asked to start again but name Insects instead. Afterwards, the main target was to study specific representations based on the material collected from phase I. Therefore, in phase II, the 20 most frequently cited non-exotic and wild vertebrates (10 items) and invertebrates (10 items) were used as stimuli. Students had one minute to write down any words, descriptions, feelings, stories or phrases that came to mind when they thought of the taxon. In this second phase, stimuli (words) were shown on a screen one by one and they had to fill 20 boxes on blank paper. Vertebrates and Invertebrates were shown alternately. Participants were asked to answer the questions spontaneously. Finally, in phase III, students had a quiz of 42 true/false questions about biodiversity and insect biology and ecology (Supplementary material A2) as a way to evaluate "actual knowledge about the group" [START_REF] Kellert | Values and perception of invertebrates[END_REF] and complete personal information gathered through the survey from phase I. Each phase lasted between 30 and 45 min at the beginning of the class. The completion of the survey and the tasks was voluntary and was anonymized by randomly giving each student the name of a scientist, a name that they kept throughout the whole process.

Taxa characterization

Each "item" cited in the first phase was coded as a Catalogue of Life taxonomical level and based on two proxies of common knowledge: Larousse dictionary descriptions and Wikipedia pages. For instance "dragonfly" is a common name for species belonging to Odonata order; "elephant", as it defines three species from different genus, was coded as the higher common level: Elephantidae family. We also characterized items by their exotic character compared to French fauna (based on the French Wildlife Inventory) and their domestic or wild status.

Data analyses

To understand the mind-bestiary of students and how cited biodiversity is perceived, first we performed a Chi-squared test to analyze whether there was an association between perceptions and the characteristics of the taxa. Then, we performed Wilcoxon signed-rank, Kruskal-Wallis and Spearman rank correlation tests to examine links between background information from the student and indicator variables of knowledge and perception (i.e. number of different cited taxa, degree of taxonomic level cited, overall perception of animals and in-sects, diversity of the vocabulary employed in phase II and the quiz score from phase III).

Table 1 Most cited vertebrate and invertebrate items used for the second free-association test and their respective assumed taxonomic level, the total number of vocabulary and the mean number of words per participant elicited. We illustrated each item with the dominant perception from phase I, the dominant Kellert's perception value (KVP) and the overall weighted polarity of the vocabulary describing the item based on the rezoJDM French lexical and semantic network database. As indicator variables were highly correlated (R > 0.6) we kept overall positive perception of insects, hereafter "sympathy for insects", as the response variable. Finally, after lemmatizing words and keeping the most frequent words (> 10%), vocabulary related to items from phase II was interpreted through two different prisms. Firstly, Kellert's perception values (KPV) [START_REF] Kellert | Values and perception of invertebrates[END_REF] -Supplementary material A3). KPV were given by three independent coders (CL, PJR and a colleague not involved in this study). Conflicting codes were discussed in order to reach an agreement on the accorded category. Then, values upon items were compared with a Chi-squared test.

Secondly, each vocabulary related to items was characterized by its polarity (positive, neutral, negative) based on the French lexical and semantic network database rezoJDM [START_REF] Lafourcade | Making people play for lexical acquisition[END_REF][START_REF] Joubert | The JeuxDeMots project is 10 years old: what we have learned[END_REF]. This database collects, since 2007, words perceptions' from on-line contributors (at least 1000 regular participants since the creation of the website of rezoJDM in 2007). As every descriptive word was on the database and had > 30 polarity attributions, we assigned to each item an overall weighted polarity reflecting the frequency of the vocabulary. Analyses were carried out using R software 3.4.1 (R Core Team, 2017). All answers were transcribed into an Excel database. Out of the 195 enlisted students in the course, only 101 completed all three phases of the experiment. Therefore, our analyses are based on the responses of those 101 participants.

3. Results

Insect perception

From the 369 different cited items, all taxonomic levels combined, none was given in its Latin name. Ten items had to be withdrawn be-cause either the item was not an Animal (Bacteria, Plant, Mushroom or Unknown). When asked which animals they knew in different types of environments, students reported firstly mammals (50.3%) and birds (15.5%). Vertebrate constituted 80.6% of cited taxa. This vertebrate diversity was characterized by 231 different items whose systemic level was particularly precise: in 55.9% of the cases it was at the genus, species or subspecies level. Taxa belonging to the Insecta class were mentioned in third place (12.4%): 41 different insect items, corresponding at 88.7% to a high-level taxonomic category (the order or the family).

Insects represented 86% of the diversity mentioned when Insects only had to be cited, the rest being other invertebrates, mainly spiders (8.2%) or earthworms (1.7%). At this time, 105 different items were cited, mostly taxa between order and family level (87.2%). Within Animals and Insects, there was a difference of appreciation based on the environment in which the item might be present (home, cities, rural and natural environments) (Fig. 1A-F) or the different nature of the items ((in)vertebrate, order) (Fig. 1G-H). Vertebrates were significantly seen more positively than invertebrates; Lepidoptera and Coleoptera items were also seen more positively than other Insecta orders.

Items from "natural landscapes" were also more appreciated than those from the urban sphere, particularly for nondomestic and in-vertebrate items. Indeed, "exotic" or "domestic" characteristics were related to positive appreciations. This result echoed literature on preferences of exotic fauna [START_REF] Ballouard | Children prioritize virtual exotic biodiversity over local biodiversity[END_REF], dislike of wilderness in 'Human spaces' such as homes and cities [START_REF] Cegarra | L'animal inventé. Ethnographie d'un bestiaire familier[END_REF][START_REF] Rupprecht | Ready for more-than-human? Urban residents' willingness to coexist with animals and plants[END_REF] and highlighted the importance of the context where the animal is represented by its perception.

In addition, we noticed that for Animals, natural environments elicited the highest number of different items (2 times more than for the others); from cities to natural environments the evenness among the most cited species significantly increased (Fig. 1A-D) which might enforce the Human and the Non-Human spaces idea. Nevertheless, for Insects, the number of items was constant through environments (Fig. 1E-F). Table 2 Participants' major characteristics: as some answers were correlated, we chose to show those who were explored for statistical tests. Participants' personal background was confronted to their overall positive perception of insects (Sympathy). Sympathy was calculated based on the mean number of "happy smileys" putted in front of invertebrate items during phase I by each participant. As a primary conclusion, animal diversity in young adult minds appeared to be biased towards positively perceived mammals which can be considered as charismatic and belonging to the 'Human sphere', and domestic animals, which are useful and historically familiar to Humans [START_REF] Cegarra | L'animal inventé. Ethnographie d'un bestiaire familier[END_REF][START_REF] Shapiro | Wildlife species preferences differ among children in continental and island locations[END_REF]. Secondly, we encounter a relatively poor invertebrate diversity in students' representations of animals, despite the fact that such diversity doubled when only insects were asked. Items cited within 'Insect' revealed the fuzziness of the concept. This was confirmed with some questions from the quiz from III rd phase: earthworms and centipedes were labelled as 'insects' in 46% and 72% of the cases, respectively. Apparently, in students' minds, Insects are firstly an archetype of non-vertebrate animal, which is more negatively seen than vertebrates. This poor knowledge about insects echoes a similar study carried out with young adults in the United-States [START_REF] Shipley | Beautiful bugs, bothersome bugs, and FUN bugs: ex-amining human interactions with insects and other arthropods[END_REF].

Values on taxa

From phase I, we acknowledged the 20 most frequent items and inputted them into the second free-association test (Table 1). Phase II vocabulary was composed of 1475 different words (all species combined). Concerning values to the most frequently cited items, we saw significant differences between taxa and (in)vertebrate qualification (Fig. 2). Vertebrates were more prone to ecologistic, humanistic and moralistic KPV than insects, while the latter had higher scientistic and negativistic values. Indeed, Insects were more prone to anatomical or behavioral descriptions (scientistic sensu KPV) rather than ecological information (interactions with other species, habitats), which was greater for vertebrates (ecologistic sensu KPV). This result might reflect that, for participants, insects are less linked to the ecosystem than vertebrates, making it difficult to see them as essential to ecosystem functioning and Human development. In fact, only "bees" had vocabulary related to utilitarian values and dominant ecologistic vocabulary. Thus, utilitarian values might not be a first good leverage to insect conservation [START_REF] Simaika | Insect conservation psychology[END_REF]. Furthermore, the description of species by striking anatomical features is typical in child-hood [START_REF] Tunnicliffe | Building a model of the environment: how do children see animals?[END_REF] which highlight the weakness of student knowledge concerning insects [START_REF] Matthews | Insects as teaching tools in primary and secondary education[END_REF]. Negativistic vocabulary such as "unpleasant", "disgusting", "harmful", "unclean" and "ugly" was inherent to all invertebrates, except the butterfly, while "dangerous" and "spiky" were the only negative vocabulary related to vertebrates ("wolf", "bear", "boar" and "hedgehog"). Only the ladybug and butterfly were described as "beautiful" and a representation of "nature"; this confirms previous studies [START_REF] Knight | Bats, snakes and spiders, Oh my!" How aesthetic and negativistic attitudes, and other concepts predict support for species protection[END_REF]Batt, 2009). This disgust driven negativistic values upon invertebrates is well known in occidental culture [START_REF] Nash | Desperately seeking charisma: improving the status of invertebrates[END_REF][START_REF] Lockwood | The Infested Mind: Why Humans Fear, Loathe, and Love Insects[END_REF].

Most frequently, taxa prone to negativistic vocabulary (fly, mosquito, cockroach) were also seen as organisms that we have to control (dominionistic values sensu KPV). Historically, the first scientific approach to insects was pest control [START_REF] Chansigaud | Des facteurs sociaux et culturels influençant la biologie de la conservation: l'exemple des Invertébrés[END_REF] and, with the sanitization of urban spaces in the 20th century, some anthropophilous taxa such as ants and cockroaches, were no longer welcomed and 'needed' to be controlled [START_REF] Blanc | La blatte, ou le monde en images In L'animal sauvage entre nuisance et patrimoine: France, xviexxie siècle[END_REF][START_REF] Frioux | Les insectes, menace pour la ville à la Belle Epoque?[END_REF]. Nevertheless, dominionistic value did not appear in [START_REF] Kellert | Values and perception of invertebrates[END_REF]survey. In our context, students were predominantly city-dwellers: maybe the wish to control the wildlife may be greater among city dwellers [START_REF] Clayton | Conservation Psychology: Understanding and Promoting Human Care for Nature[END_REF][START_REF] Rupprecht | Ready for more-than-human? Urban residents' willingness to coexist with animals and plants[END_REF]. This logically follows phase I results which showed a more positive perception on fauna from "natural landscapes" (Fig. 3). Moreover, even if it was not possible to compare it statistically because of the small number of words (N = 75/10,485), vertebrate species elicited words or sentences referring to conservation concern, especially wild carnivores such as the Bear and the Wolf, while in-vertebrates did not. Some differences can be pointed out between participants' perceptions and polarity form the rezoJDM database (Table 1). Indeed, rezoJDM vocabulary tended to be more neutral for Ladybug and Mosquito, items that are supposed to be strongly positive and negative respectively in students' representations. This might come from the rezoJDM database itself, which gathers personal contributions without any semantic or environmental context. Nonetheless, in most of the cases it was concordant with participants' responses, echoing with a larger panel of persons and therefore confirming the validity of our public to probe general insect perception.

Knowledge, personal construction and perception

Sympathy for six-legged creatures, an overall positive perception of Insects from phase I, varied depending on the participant's sensitive social environment and place where participants declared growing up. While the "growing up environment" related to sympathy result echoed with KPV results from phase II and thus place dependent perception's from phase I, the influence of a rich and close sensitive to nature social environment was new in the context of insects' perceptions and re-presentations. Nevertheless, there was no significant difference be-tween gender, actual knowledge (quiz from phase III, diversity of items) nor practice of outdoor activities or parents' environmental related profession in relationship to "sympathy for insects" (Table 2). Sympathy for insects thus might be a construction from a specific moment a specific person, independently from formal knowledge [START_REF] Chawla | Le soin de la nature chez les enfants et les adolescents. Expériences marquantes pour le développement du sens de la connexion[END_REF][START_REF] Shipley | Beautiful bugs, bothersome bugs, and FUN bugs: ex-amining human interactions with insects and other arthropods[END_REF].

Discussion

4.1. Getting a picture of Insecta Insect conservation is a complex problem that cannot be easily ad-dressed without an interdisciplinary approach. Our workflow enabled us to go from a perceived animal diversity panel to a specific panel of perceived "insects" before narrow known into representations. Now, what can we offer to address the "perception challenge" in our context? Phase I showed us that, even if invertebrates were less frequently cited than vertebrates and were more negatively perceived or de-scribed, they were not completely absent. This result allows us to see the base upon which we can build a strategy for insect conservation through perception change. Indeed, a positive or a negative perception is a first leverage: it means engagement rather than disinterest [START_REF] Clayton | Conservation Psychology: Understanding and Promoting Human Care for Nature[END_REF]. "Butterfly", "bee" and "ladybug", with overall positive perceptions and previously mentioned as charismatic [START_REF] Snaddon | A child's eye view of the insect world: perceptions of insect diversity[END_REF][START_REF] Small | The new Noah's Ark: beautiful and useful species only. Part 1. Biodiversity conservation issues and priorities[END_REF][START_REF] Barua | Selecting flagships for in-vertebrate conservation[END_REF], came in the top ten of mentioned taxa but only when asking 'Insects only'. Thereby, first six-legged to pop-up in participants' minds while we call for Animals are "problematic" and "harmful" items. Concordantly, when thinking about Insects only, problematic species appear first, but then useful and charismatic in-vertebrates are also mentioned. Which means that, whatever the con-text, 'Insect' elicits first a negative image. Indeed, first-mentioned invertebrates are neither "beneficial" nor "charismatic", but can be related to diseases (mosquito, fly) or fears (spider) [START_REF] Merckelbach | Fear of animals: correlations between fear ratings and perceived characteristics[END_REF]Batt, 2009;[START_REF] Lockwood | The Infested Mind: Why Humans Fear, Loathe, and Love Insects[END_REF]; indeed, the most common animal phobias are entomophobia and arachnophobia [START_REF] Lelord | La force des émotions: amour, colère[END_REF] and indeed in our study 21% of participants spontaneously mentioned a fear related to invertebrates. General literature [START_REF] Raffles | [END_REF][START_REF] Lockwood | The Infested Mind: Why Humans Fear, Loathe, and Love Insects[END_REF] and scientific studies [START_REF] Kellert | Values and perception of invertebrates[END_REF][START_REF] Costa-Neto | Considerations on the Man/Insect Relationship in the State of Bahia, Brazil in Insects[END_REF] argue that insects are associated with fear, disease and damage in different cultures, which puts them in the "no" box of conservation. Actually, in a parallel study conducted with 180 psychology students, participants were less willing to engage in conservation for insects than for mammals and birds, and, if they were, it would be for their utility rather than their aesthetic or intrinsic values (CL, unpublished). [START_REF] Nash | Desperately seeking charisma: improving the status of invertebrates[END_REF] paraphrased this in his paper title: "Desperately Seeking Charisma: Improving the Status of Invertebrates". Although charisma plays a major role at present in obtaining social and financial support for conservation [START_REF] Mace | Prioritizing choices in con-servation[END_REF], this quality is mostly the privilege of species taxonomically nearer to Humans [START_REF] Stokes | Things we like: human preferences among similar organisms and implications for conservation[END_REF]Batt, 2009). If empathy, which is a response to the emotional and cognitive connection made by perceptions and re-presentations, is a predictor of pro-environmental behavior [START_REF] Chawla | Growing up green: becoming an agent of care for the natural world[END_REF][START_REF] Kals | Emotions and environment[END_REF], insect conservation is seriously disadvantaged [START_REF] Lorimer | Nonhuman charisma[END_REF][START_REF] Lockwood | The Infested Mind: Why Humans Fear, Loathe, and Love Insects[END_REF] and desperately seeking charisma in insects may be not the way forward into unbiased (insect) conservation. Maybe the way is ahead an acceptation of this primary negative attitude. While perceptions cannot be easily changed, particularly for in-vertebrates in the point of view of disgust/fearevolutionary response (Batt, 2009;[START_REF] Lockwood | The Infested Mind: Why Humans Fear, Loathe, and Love Insects[END_REF], they can be demystified to get in-vertebrate tolerance if not sympathy in a first stage [START_REF] Lockwood | The Infested Mind: Why Humans Fear, Loathe, and Love Insects[END_REF][START_REF] Schonfelder | Individual perception of bees: between perceived danger and willingness to protect[END_REF]. Based on vocabulary used in phase II we can already work with participants to explain that bees 'sting' and spiders bite as a defense, they do not 'aggress'; not all cockroaches are pests; ants, cockroaches and scarabs are not 'unclean', they are 'cleaners'; Mosquitos are not 'useless', they are a part of a greater food web and play a part in ecosystem functioning, etc. Empathy could come though halo effect when comparing to "good", "non harmful" and useful species when demystified.

A roadmap from perception to conservation

The shift of perception and the durability of this change need scientific evidence of the interrelationship between species, original features on which we can reflect or engage and even demystify [START_REF] Schultz | Promoting pro-environmental behavior[END_REF]. Knowledge and understanding of the natural world can arise from outdoor direct experiences and/or (in)formal education [START_REF] Chawla | Growing up green: becoming an agent of care for the natural world[END_REF][START_REF] Prévot | The relationship of childhood upbringing and university degree program to environmental identity: experience in nature matters[END_REF]. Difficult as it seems, perception shift is not impossible, as it has operated for Birds in the late years of the 20th century [START_REF] Chansigaud | Des hommes et des oiseaux: une histoire de la protection des oi-seaux[END_REF], Primates and the wolf [START_REF] Almedia | Changing negative perceptions of animals through teaching practice: a research in primary education[END_REF] in the United States and, in recent years, Hymenoptera pollinators [START_REF] Williams | Bumblebee vulnerability and conservation world-wide[END_REF][START_REF] Sing | Diversity and human perceptions of bees (Hymenoptera: Apoidea) in Southeast Asian megacities[END_REF]. However, they need to pass through the right catalyzer, which can influence re-presentations' construction journey.

Is it the use of common names? We need to consider that the significance and images behind the names. Moreover, they elicit and the representations they might reflect should be understood in the socio-cultural context [START_REF] Bang | Cultural mosaics and mental models of nature[END_REF][START_REF] Wan | Shared knowledge matters: culture as intersubjective representations[END_REF]. Here, ant was a symbol of collective "work" and "intelligence" and scarab of "Egypt". Costa-Neto (1998) showed that in northern Brazil "Abeia" label ("Bee") was used for 23 different taxonomic terms from Apidae and Vespidae families, while in our context it is restricted to the honeybee. This is consistent with the result obtained by [START_REF] Schonfelder | Individual perception of bees: between perceived danger and willingness to protect[END_REF] with German students ranging from primary school to university. Thus, "bee" is not a catalyzer of "wild bees" representation.

Our study shows that the perception of insects by Humans is com-plex and taxa dependent. Furthermore, our results underline that a relative "sympathy" for insects is more likely to be related to a sensitive regard (accompanied observation and valuation, i.e. joint attention) and an exposure to nature during childhood, which has been largely studied in conservation education and psychology [START_REF] Chawla | Childhood experiences associated with care for the natural world: a theoretical framework for empirical results[END_REF][START_REF] Myers | Children and nature[END_REF]. Contrary to people questioned by [START_REF] Kellert | Values and perception of invertebrates[END_REF], students from the early 21st century did not associate insects with an outdoor experience (naturalistic values); moreover, 'practice of outdoor activities' did not influence their "sympathy" for the six legged, letting us think that the environment alone is not enough to get a representation of insects. A study by [START_REF] Tunnicliffe | Building a model of the environment: how do children see animals?[END_REF] showed that children learned names and attributes of animal taxa essentially from home and, secondly, by joint direct observation. [START_REF] Chawla | Life paths into effective environmental action[END_REF] showed that 77% of people who followed a proenvironmental life path evoked family, particularly parents, as triggers of this choice. A high quality sensitive social entourage -key socializers [START_REF] Chawla | Growing up green: becoming an agent of care for the natural world[END_REF][START_REF] Collado | The role of parents and best friends in children's proenvironmentalism: differences according to age and gender[END_REF]-can direct attention to the value of invertebrates and engage for "insect sympathy". Based on such observations, and knowing that the Human-Insect relationship is conditioned by an evolutionary and cultural heritage [START_REF] Lockwood | The Infested Mind: Why Humans Fear, Loathe, and Love Insects[END_REF], we encourage to build holistic instruction of bio-logical diversity and importance accompanied by highly influential persons (school teachers and parents) to diminish the perception challenge from insect conservation effort. Parents and teachers should be able to follow training programs by NGOs and entomologists in order to sensitize to insects and connectedness of such diversity to other species and ecosystems, and thus improve the likelihood to sensitize others [START_REF] Matthews | Insects as teaching tools in primary and secondary education[END_REF][START_REF] Wagler | External insect morphology: a negative factor in attitudes toward insects and likelihood of incorporation in future science education settings[END_REF]. The classroom is a great moment in which there is a teacherstudents joint attention; involving parents in such moments should increase the sensitizing effect on insect perceptions and lead to positive attitudes. Examples of demystification, linkage to ecological challenges (i.e. reduction of pesticides, biodiversity interactions sustainability) and the use of non-charismatic taxa during class are the "Mosquitoes in the Classroom" [START_REF] Matthews | Insects as teaching tools in primary and secondary education[END_REF] and Cowles' (1984) "cockroaches".

Conclusion

We must encourage ecologists, teachers and NGOs to rethink the way they educate the public to effectively reach comprehension through the right words and actions. The success of protection and conservation plans largely depends upon the public's understanding and implication. Our study underlined the importance of bias in the public's representation of insects. An analogous situation may appear for all different sociodemographic categories (farmers, pest managers, politicians…). This awareness is imperative and a prerequisite to enable general every citizen to engage in dialogue, develop a common vision of insects and contribute together to establish effective and timely biodiversity preservation.

Furthermore, stablish a roadmap to conservation based on public's conservation psychology should go beyond insects: it is imperative to acknowledge the diversity of biodiversity. Shifting from species to ecosystems should be the future of environmental education to reach an inclusive conservation approach [START_REF] Simaika | Insect conservation psychology[END_REF]. This research did not receive any specific grant from funding agencies in the public, commercial, or not-for-profit sectors.

Fig. 2 .

 2 Fig. 2. Number of entries per word coded into Kellert's perception values, in a logarithmic scale. To illustrate each value, we putted an icon representing the items (vertebrates on grey, insects in black) which were the most frequently cited (p-value < 0.001 = ***). Icons made by Freepick from www.flaticon.com, CC BY SA license.

Fig. 3 .

 3 Fig. 3. Word cloud representation: the most frequently cited vocabulary (> 10%) for four invertebrate items from phase II: the bee, the cockroach, the mosquito and the ladybug. The length of the font is proportional to the frequency of the word. The color of words represent the overall polarity (positive, negative or neutral) extracted from the rezoJDM French lexical and semantic network database. Icons made by Freepick from www.flaticon.com, CC BY SA licence. (For interpretation of the references to colour in this figure legend, the reader is referred to the web version of this article.)

  Levels were estimated depending on the number and the nature of the persons evoked[START_REF] Collado | The role of parents and best friends in children's proenvironmentalism: differences according to age and gender[END_REF]). b Levels were estimated depending on the number and frequency of mentioned activities.

	Characteristics	Summarized answers	~Sympathy
	Average age	21 ± 4 years old (range 17-50 years)	R = 0.15	p-Value = 0.16
	Gender	58.4% women; 38.6% men; 1.9% "other"	U = 825.5	p-Value = 0.5
	Parents with environmental related professions	9% yes; 91% no	U = 384.5	p-Value = 0.72
	Presence of a rich sensitive social environment	83.3% yes [divides into 11 levels a ]; 26.7% no	R = 0.25	p-Value = 0.031
	Environment where they grew up	49% rural; 35% urban; 16% both	χ	2 = 122,4	p-Value = 5.24e-29
	Outdoor activities practice (athletic, artistic, camping…)	92% yes [divided into 4 classes b ]; 8% no	R = 0.07	p-Value = 0.95
	Nature related fear	66.6% yes (36.6% being invertebrates); 33.3% no	U = 543.5	p-Value = 0.31

a

Acknowledgments

We would like to thank T. Bodaud, A. Léocadie and B. Louboutin for assistance in conducting and coding our surveys and free-association tests. We also would like to acknowledge P.Y. Hardy, G. Cohen and journal reviewers, whose comments greatly improved the manuscript.

Appendix A. Supplementary data Supplementary data to this article can be found online at https:// doi.org/10.1016/j.biocon.2019.07.031.


T Sylvestre
email: thibaut.sylvestre@univ-fcomte.fr

A R Ragueh

M W Lee

B Stiller

G Fanjoux

B Barviau

A Mussot

A Kudlinski

Black-light continuum generation in a silica-core photonic crystal fiber

We report the observation of a broadband continuum spanning from 350 to 470 nm in the black-light region of the electromagnetic spectrum as a result of picosecond pumping a solid-core silica photonic crystal fiber at 355 nm. This was achieved despite strong absorption and a large normal dispersion of silica glass in the UV. Further investigations reveal that the continuum generation results from the interplay of intermodally phase-matched fourwave mixing and cascaded Raman scattering. We also discuss the main limitations in terms of bandwidth and power due to temporal walk-off, fiber absorption, and the photo darkening effect, and we suggest simple solutions.

Over the last few years, there have been a number of important efforts to extend the blue and UV sides of supercontinuum (SC) generation in silica-core photonic crystal fibers (PCFs) [1][2][3][4][5][6]. These efforts are motivated by applications of broadband UV light in biomedical sciences and spectroscopy. While most of the experiments have been performed by pumping in near-IR (NIR) or visible regions, it is remarkable that the use of laser emitting in the UV as a pump for SC generation in PCF has not yet been endeavored. Generation of UV broadband light has, however, recently been reported in a single-mode high-OH fiber [7].

Herein, we demonstrate that despite both the strong absorption and large normal dispersion of silica in the UV, a broadband continuum can be efficiently generated in the black-light region of the electromagnetic spectrum by pumping a PCF with a picosecond microchip laser at 355 nm. The PCF is a standard solid-core silica PCF made by IRCICA. It is similar to those usually used for SC generation when pumping at 1064 nm in the small anomalous dispersion regime [8]. It has a triangular lattice with a pitch and hole diameter of 3.88 and 2.73 μm, respectively. Its cross-sectional image is depicted in Fig. 1(a) together with its dispersion curve for the fundamental mode around 355 nm. At this wavelength, our PCF exhibits a large normal group-velocity dispersion (GVD) dominated by material dispersion. In addition, the PCF carries several propagation modes. Three main transverse modes have been identified numerically using a finite element method. These modes are depicted in Figs. 1(b) and 1(c) together with their inverse group velocities and dispersion curves, respectively. The nonlinear coefficient is γ 34 W -1 km -1 for the fundamental mode, and its zero-dispersion wavelength (ZDW) is 1044 nm. The fiber loss at 355 nm was measured as 0.5 dBm -1 . As a pump laser, we used a passively Q-switched frequency-tripled Nd:YAG laser (Teemphotonics Powerchip Series) emitting 300 ps pulses (FWHM) at a repetition rate of 1 kHz and an average power of 22 mW. The output was coupled into our PCF by a 10× microscope objective. The output spectra were recorded using an optical spectrum analyzer, and the continuum formation was analyzed by means of a variable attenuator. We also used a grating spectrometer (2400 l∕mm) and a CCD color camera for modal and spectral analysis. Figure 2 shows the output spectra after 30 m of fiber for an increasing coupled pump power ranging from 0.5 to 4 mW. We can clearly see the continuum generation that starts from the pump wavelength and broadens up to the blue. The widest continuum spans 120 nm, from 350 to 470 nm, with an output power of 120 μW. This corresponds to a low spectral power density of only 1 μW∕nm. The image in the inset shows the optical mode output of the widest continuum recorded by the color camera. The UV light appears as white, whereas the visible light is in true color. This image shows the continuum is mainly carried by the LP 31 mode. Figure 3 generation by cutting the fiber back to 1 and 4 m, respectively, keeping the same injection conditions. As can be seen in Fig. 3(a), we identify a preliminary intermodal four-wave mixing (FWM) process involving the pump (labeled P) in a mixed-mode distribution (see top image), an anti-Stokes sideband (AS 1 ) in the LP 01 mode, and a Stokes one (S 1 ) in the LP 11 mode. The phase-matching condition for this modal FWM process reads as κ

β 11 1 -β 01 1 Ω β 2 Ω 2 2γP [9]
, where the first, second, and third terms represent the contributions of modal and chromatic dispersion and nonlinearity, respectively, to the phase mismatch. Ω 2π is the FWM frequency shift. β 11 1 and β 01 1 are the inverse group velocities of the LP 11 and LP 01 modes. β 2 is the GVD coefficient at pump wavelength. Figure 1(d) shows the FWM frequency shift versus the pump wavelength calculated from the above equation. At 355 nm, we found a frequency shift of 6 THz, in good agreement with the measurement of Fig. 3(a).We have also checked that all other possible FWM processes involving other modes are not phase-matched. For Fig. 3(b), the pump power exceeds the Raman threshold, which yields two strong first-and second-order Raman Stokes R 1 and R 2 . Simultaneously, parametric Stokes band S 1 acts as a second pump and generates both harmonic sideband S 2 and its own first-order Raman Stokes (SR 1 ). Surprisingly, we also observe the efficient generation of two anti-Stokes bands, AR 2 and ASR 2 , far from the pump. We have checked that these waves result from FWM involving six waves, namely the pump P, the parametric band S 1 , and Raman Stokes waves SR 1 and second-order R 2 . In particular, AR 2 at 344 nm has been identified as being second-order Raman anti-Stokes upshifted by 26 THz from the pump. To our knowledge, this is the first time that second-order anti-Stokes was efficiently generated in the absence of first-order [10]. We have indeed verified that theses waves are phasematched in higher-order modes of the PCF and fall far from the Raman absorption band. At higher pump power, all Raman and parametric bands together merge and, because of the large Raman gain bandwidth, the CRS evolves toward a smooth continuum, as those shown in Fig. 2. This spectral broadening dynamics is analogous to the one previously reported using visible 532 nm pump pulses propagating in a dispersion-shifted fiber [9]. Note also that all the anti-Stokes waves reported in Fig. 3 no longer appear in Fig. 2 because of absorption. Moreover, all Raman Stokes bands are mainly carried by the LP 31 mode, which explains the optical mode distribution of Fig. 2.

Figure 4 compares the UV continuum generation with that generated by an IR subnanosecond microchip laser at 1064 nm ,close to the ZDW of the PCF [8]. The experiments have been performed by replacing the UV laser by the IR one, keeping the same PCF, but with different coupled pump power. As can be seen, the SC generation using the IR pump spans more than two octaves from 450 nm to more than 1800 nm, whereas the UV continuum is limited to a third of an octave only. However, the latter covers a new UV-visible spectral window that is not accessible with the IR pump. Let us now discuss the main limitations. The most important ones are fiber absorption and the photodarkening effect caused by UV radiation. We have indeed observed that the continuum bandwidth strongly decreases after about 20 min due to solarization. These detrimental effects could be mitigated by using specialty high-OH or solarization-resistant optical fiber, as in Ref. [7]. The third drawback is the large normal dispersion of silica that induces a strong pulse walk-off among the Raman pulses and thus limits the continuum extension toward longer wavelengths. This can be easily overcome by using longer nanosecond pulses. To verify the impact of walk-off, we performed split-step numerical simulations based on the generalized nonlinear Schrödinger equation, including the full Raman susceptibility and the wavelength-dependent absorption. As initial conditions, we consider a picosecond pump pulse at 355 nm together with the parametric band S 1 with half of the power to mimic the FWM of Fig. 3. Including the multimode behavior and the FWM intermodal coupling in the numerics is actually very time-consuming and computationally intensive. We also used the one-photon-per-mode model as an input condition. Figures 5(a)-(d) show the results of our numerical computations for 30 m of singlemode nonlinear propagation and for two pulse durations. As can be seen in Fig. 5(d), for a 500 ps pulse duration, a sixth-order Raman cascade is generated, whereas only four Raman orders occur for a 300 ps pulse duration [Fig. 5(b)]. Figures 5(a) and 5(c) show the corresponding temporal intensities. In both traces, we can clearly identify a train of noiselike Raman pulses that are optically delayed by walk-off. The temporal walk-off is about 300 ps, which is close to the pump pulse duration. Consequently, the Raman pulses do not overlap at all after 30 m of propagation, thus limiting the Raman cascade, as shown in Figs. 5(b) and 5(d). For comparison, we have analytically calculated the Raman pulse walk-off from the following expression: T D:L:Δλ, where Δλ is the Raman shift in wavelength. We found a pulse walk-off of 288 ps for L 30 m, in good agreement with numerical simulations. Finally, the numerical simulation of Fig. 5(e) was realized with the same conditions but at a higher peak power of 3 kW. It shows that the CRS evolves into a continuum that spans from 355 to about 430 nm, in rather good agreement with the experimental one shown in green in Fig. 2.

In conclusion, we reported the observation of a broadband black-light continuum in a solid-core silica photonic crystal fiber as a result of pumping at 355 nm. The continuum generation has been identified as resulting from the interplay between intermodal FWM and Raman generation. This fiber-format broadband IR-free black-light source could find possible applications as a Wood's lamp for multicolor excitation of fluorescent proteins in medicine, dermatology, molecular biology, or gas absorption spectroscopy [7,11]. Further progress will be pursued in the near future to improve the continuum bandwidth and spectral power density by using solarization-resistant silica optical fibers.

Fig. 1 .

 1 Fig. 1. (Color online) (a) Chromatic dispersion of the fundamental mode versus wavelength. Inset: SEM image of the solid-core PCF. (b), (c) The inverse group velocities and the chromatic dispersions of the three LP 01 (red), LP 11 (green), and LP 31 (blue) modes, respectively, shown in the insets. (d) FWM frequency shift versus wavelength. (See Media 1.)

Fig. 2 .Fig. 3 .

 23 Fig. 2. (Color online) Output spectra recorded at the end of the 30 m long PCF for a variable coupled pump power from 0.5 to 4 mW. The spectral resolution is 0.5 nm. The inset shows the optical mode output of the blue continuum.

Fig. 4 .Fig. 5 .

 45 Fig. 4. (Color online) Direct comparison of spectra recorded at the output of the PCF under UV (355 nm, blue) and IR (1064 nm, red) laser pumping. Pump powers are 4 and 25 mW, respectively. (b) A zoom of the part of (a) shown in the dashed box.


Nour El

Hoda Djidi

Matthieu Gautier
email: matthieu.gautier@irisa.fr

Antoine Courtay
email: antoine.courtay@irisa.fr

Olivier Berder
email: olivier.berder@irisa.fr

Enhancing Wake-Up Receivers Reliability Through Preamble Filtering and Minimum Energy Coding

Keywords: Minimum energy coding, Reliability, Wake-up receivers, Wireless sensor networks, Energy efficiency, IoT

Wake-up Receivers (WuRs) represent one of the most promising solutions for allowing an ultra low power consumption in wireless sensor networks. However, WuRs have several limitations such as low sensitivity, inducing a miss-interpret of the wake-up signal, and thus a performance degradation of the whole system. This work introduces two complementary schemes, namely minimum energy coding and preamble filtering, in order to enhance the WuR reliability while being energy efficient. It is shown through experimental measurements an enhancement on the reliability up to 22% and a total energy saving of 42% while applying minimum energy coding. Moreover, a significant reduction of the false wake-up is realized through preamble filtering.

I. INTRODUCTION

Internet of Things (IoTs) is rapidly gaining ground in several fields such as smart cities, e-health and smart farms. The things forming wireless sensor networks are low power and resourceconstrained devices. Traditionally, the energy consumption of the wireless communications is reduced by using duty-cycled protocols. However, this technique still wastes energy due to idle listening and overhearing [START_REF] Djidi | Adaptive relaying for wireless sensor networks leveraging wake-up receiver[END_REF].

In recent years a new promising wireless technology has emerged, called Wake-up Receiver (WuR), allowing an asynchronous communication with an ultra low power consumption and a low latency [START_REF] Piyare | Ultra Low Power Wake-Up Radios: A Hardware and Networking Survey[END_REF], [START_REF] Djidi | How can wake-up radio reduce lora downlink latency for energy harvesting sensor nodes?[END_REF]. WuR consists in a secondary ultra low power receiver that is always listening to the channel, consuming orders of magnitude less power than traditional receivers. The WuR wakes up the main receiver from sleep state when a specific signal, called Wake-Up Beacon (WUB) is received. The WUB consists in a preamble and a destination address. The preamble wakes up the Ultra Low Power (ULP) Microcontroller (MCU) of the WuR that decodes the received address. However, the WUB is prone to channel errors which induces either missed wake-up (when the WuR receives an incorrect address and will not wake up the main node while it should) or false wake-up (when the WuR will wake up the main node while it should not).

Errors can be reduced through channel coding by adding some extra bits. Rakovic et al. presented in [4] a channel coding to improve the reliability and the energy consumption of WuR. The study compares the performance of Hamming code, repetition code and Walsh code. Walsh code outperforms all these codes, but it requires a large addressing size (32B) and thus a high memory cost that is practically impossible.

We propose in this work two complementary schemes to improve the WuR reliability and reduce the false wake-up and the missed wake-up while being energy efficient. The first one concerns the preamble and consists in filtering a valid preamble duration by the ULP-MCU before checking the correctness of the address in the WUB. To the best of our knowledge, no previous work proposed to check the validity of the preamble, which is just used to wake up the ULP-MCU of the WuR. The second scheme deals with the received address and resides in applying Minimum Energy (ME) coding. This scheme works for WuRs based on On-Off Keying (OOK) as are most of WuR circuits [START_REF] Piyare | Ultra Low Power Wake-Up Radios: A Hardware and Networking Survey[END_REF], and its performance efficiency was proven by Tanget et al. in [START_REF] Tang | BER performance analysis of an on-off keying based minimum energy coding for energy constrained wireless sensor applications[END_REF] for this type of circuits.

This paper is organized as follows. In Section II, both WuR circuit design and the preamble filtering technique are given. ME coding principle and energy consumption model are addressed in Section III. Section IV presents experimental measurements and analytical evaluation of different performance metrics of the WuR. Finally a conclusion is given in Section V.

II. WAKE-UP RECEIVER AND PREAMBLE FILTERING

A. Wake-up receiver circuit design

WuR is an ultra low power receiver that is continuously listening to the channel, while the main node is in sleep mode. Most circuits design in the literature are based on OOK demodulator [START_REF] Piyare | Ultra Low Power Wake-Up Radios: A Hardware and Networking Survey[END_REF]. Fig. 1(a) shows the block diagram of the WuR based on non-coherent OOK receiver that was considered in this work [START_REF] Magno | Design, Implementation, and Performance Evaluation of a Flexible Low-Latency Nanowatt Wake-Up Radio Receiver[END_REF]. The first stage contains a matching filter that guarantee the maximum transfer of power from the antenna to the receiver circuit at 868 MHz. Then, an envelope detector rectifies the bandpass signal to a baseband signal. This signal passes through a comparator to reconstruct the bits of the WUB. After the comparator, a low pass filter acts as a preamble detector that induces a delay of t d as shown in Fig. 1(b). If the preamble duration is longer than t d , then the preamble detector generates an interrupt to wake up the ULP-MCU. Finally, the ULP-MCU decodes the received WUB.

B. Preamble filtering

The WUB comprises two fields, the first one is a preamble of l pr bits that traditionally serves to wake up the ULP-MCU, and the second field contains the destination address as illustrated in Fig. 1(b). When the received address corresponds to the destination node, the ULP-MCU generates an interrupt to wake up the main node. The novel technique that we propose is that the ULP-MCU filters the preamble once it is woken up after a delay t d . If the preamble duration denoted t pr (Fig. 1(b)) is in a predefined interval, that corresponds to the duration of a valid preamble, then the ULP-MCU continues decoding the address, otherwise it is turned off. This technique will reduce the false wake-up that occur due to other signal in the 868 MHz band. Indeed, it could exist external signals that have different preamble duration and will be interpreted as valid WUB if the preamble is not checked and the address corresponds to the destination node. Thus, the ULP-MCU will wake up the main node via an interrupt, while it should not, which will induce a waste of energy.

B. Energy consumption model

A point-to-point communication between a transmitter and a WuR is considered. The transmitter keeps transmitting the same packet N tx times until it is successfully received. N tx is expressed as:

N tx = 1 1 -M W R , (1)
with M W R the Missed Wake-up Rate.

The average power consumption of both transmitter and WuR will be presented with the two different scheme, i.e. uncoded scheme and when applying ME (n, k).

1) Average power consumption with uncoded scheme:

• Transmitter power consumption: The average power consumption of the WUB transmission until it is successfully received denoted P uncoded tx is:

P uncoded tx = N tx λt b • P tx1 • (l pr + k 2 ) + P tx0 • ( k 2
) ,

(2) with P tx1 and P tx0 the power consumed to send '1' and '0', respectively, t b the bit duration, k the number of bits used in the address and λ the packet transmission rate.

• WuR power consumption: The average power consumed by the WuR denoted P uncoded W uR is:

P uncoded W uR = N tx λ(t pr + kt b ) • P wur rx + (1 -N tx λ(t pr + kt b )) • P wur idle , (3)
with P wur rx the power consumed by the WuR when receiving and processing the WUB, and P wur idle the power consumed by the WuR when it is listening to the channel while the ULP-MCU is sleeping.

2) Average power consumption with ME (n,k) scheme:

• Transmitter power consumption: The average power consumption of transmitting the WUB until it is successfully received when using ME (n, k) denoted P M E tx is:

P M E tx = N tx λt b • P tx1 • (l pr + n n + 1 ) + P tx0 • ( n 2 n + 1
) .

(4) • WuR power consumption: The average power consumption of the WuR based on ME denoted P M E W uR is given by: (5)

IV. PERFORMANCE EVALUATION

A. Preamble filtering

Two different schemes of decoding the received WUB were implemented in the WuR designed in [START_REF] Magno | Design, Implementation, and Performance Evaluation of a Flexible Low-Latency Nanowatt Wake-Up Radio Receiver[END_REF] that has a measured sensitivity of -45dBm and is working at 1kbps. The traditional does not check the duration of the preamble and then starts decoding the received address right after the end of the preamble, and the novel scheme is by filtering the received preamble duration. A valid preamble contains l pr of 3 bits and t d is around 400 µs, therefore if the preamble duration t pr is between 2.4 ms and 2.7 ms, then it is considered as a valid one and thus the ULP-MCU decodes the received address, otherwise it is turned off.

1) False wake-up measurements: The WuR was placed 24h in a laboratory office listening to the channel, no WUB was sent and the number of false wake-up was measured.

Fig. 2 shows the false wake-up amount as a function of the received addresses of 8 bits. It can be seen that there are several false wake-up, as the WuR is based on OOK detector so any presence of an external signal of another wireless technology with different modulation is translated to a bit '1' and an off signal is translated to a bit '0'. Fig. 2 also shows that filtering the preamble considerably reduces the number of false wake-up and thus avoiding the wake-up of an undesirable node. If the node address is for example 4, it can be seen that 4154 false wake-up occur with unfiltered preamble against 16 with filtering. 99.6% of false wake-up are thus reduced with preamble filtering, which will reduce the energy consumption of 259.6 times. For some addresses, such as the address 170, there are no false wake-up with both schemes. The total false wake-up is 120139 with unfiltered scheme against 982 with preamble filtering, thus 99% of all false wake-up are reduced with preamble filtering, with a total energy saving up to 122.34 times. The same experiment was done in a house, the total false wake-up in 24 h was equal to 27457 when not filtering, against zero false wakeup when filtering. This reduction amount clearly depends on the environment in which the WuR is located. Regardless of the environment, the preamble filtering will reduce the false wake-up and the energy consumption.

B. ME coding

1) Bit error rate evaluation:

To demonstrate the efficiency of ME coding, the theoretical bit error probability from [START_REF] Tang | BER performance analysis of an on-off keying based minimum energy coding for energy constrained wireless sensor applications[END_REF] N0 that is at some specific level of BER when coding is used compared to the uncoded scheme. It is apparent from Fig. 3 that with a BER of 10 -4 , a coding gain of 1.9dB, 2.5dB and 3.4dB, respectively is achieved with ME (7,3), ME (15,4) and ME (63,[START_REF] Magno | Design, Implementation, and Performance Evaluation of a Flexible Low-Latency Nanowatt Wake-Up Radio Receiver[END_REF]. It can also be seen that at the same level of E b N0 , the BER is reduced when applying ME coding, thus ME coding can either improve

E b
N0 at a fixed level of BER or reduce the BER at a fixed E b N0 . It can also be seen that the higher the size k is, the more the performance of ME coding is improved. However, using a large value of k will induce more latency and more power consumption. Therefore ME [START_REF] Schwartz | Communication systems and techniques[END_REF][START_REF] Djidi | How can wake-up radio reduce lora downlink latency for energy harvesting sensor nodes?[END_REF] is implemented in real field and the experimental results are given in the next Section.

2) Missed wake-up measurements: The M W R are measured for 7215 WUB packets sent at a rate of 4 packets/s. The WuR and the transmitter are placed at a distance of 1 m from each other in an anechoic chamber. The M W R are measured for different transmission power levels ranging from -13 dBm to -19.5 dBm and these results are expressed in theoretical range by considering the Friis formula [START_REF] Schwartz | Communication systems and techniques[END_REF] and a transmission power of 10 dBm. Fig. 4 illustrates the M W R as a function of the range. It can be seen that below a range of 22 m, the M W R is the same when applying ME (7,3) and with uncoded scheme. When the range exceeds 22m, ME (7,3) improves the M W R. At a range of 28 m the M W R is reduced by 22%.

3) Energy consumption evaluation: The transmitter from ST which is considered [START_REF] St | Ultra-low power high performance sub-1 GHz transceiver Datasheet[END_REF] has P tx1 and P tx0 equal to 3.8mW and 420 µW, respectively. For the WuR designed in [START_REF] Magno | Design, Implementation, and Performance Evaluation of a Flexible Low-Latency Nanowatt Wake-Up Radio Receiver[END_REF], P wur rx and P wur idle are equal to 284µW and 1.83µW, respectively. t b is equal to 1ms and λ is fixed at 1packet/s. These values are used to feed the models given in Section III-B. Fig. 5(a) shows the average power consumption of the transmitter per successful packet when using both uncoded and ME [START_REF] Schwartz | Communication systems and techniques[END_REF][START_REF] Djidi | How can wake-up radio reduce lora downlink latency for energy harvesting sensor nodes?[END_REF] schemes. It can be seen that ME consumes less than uncoded scheme, as with ME coding more '0' are transmitted consuming less power than '1'. When the range is under 22 m, ME (7,3) consumes 8.7% less than uncoded scheme, and beyond 22 m the gain becomes more important achieving 43.9% at a distance of 28 m, as at a longer range the transmitter with uncoded scheme has a higher M W R and thus needs to re-transmit more packets than ME [START_REF] Schwartz | Communication systems and techniques[END_REF][START_REF] Djidi | How can wake-up radio reduce lora downlink latency for energy harvesting sensor nodes?[END_REF]. Fig. 5(b) illustrate the average power consumption of the WuR per successful packet. It can be seen that ME consumes more than uncoded scheme as the WuR should decode a longer packet with ME coding. It consumes 43% more than uncoded scheme, but it is in the order of few micro-watts. Fig. 5(c) details the total average power consumption of both transmitter and WuR per successful packet. It is apparent that uncoded scheme consumes more than ME coding. The higher the range is, the more the energy is saved with ME. At a range under 22 m, ME coding saves 5.58% of energy, and at a range of 28 m 41.76% of energy is saved.

V. CONCLUSION

This paper presented two schemes that can be applied to WuR to enhance its reliability and save energy. The first one is to filter the received preamble and accept only a valid one to decode the received address. The other scheme is to apply Minimum Energy coding (ME). A detailed study of the energy consumption was presented. Both preamble filtering and ME coding were implemented in a real platform and the false wake-up and missed wake-up were measured. Results show that ME reduces the missed wake-up up to 22% and saves 42% of the total energy. It also appears the efficiency of filtering a valid preamble in reducing 99% of false wake-up.

  (a) WuR block diagram. (b) ULP-MCU activity as a function of the comparator output.

Fig. 1 :

 1 Fig. 1: WuR system design.

Fig. 2 :+ ( 1 -

 21 Fig. 2: Number of false wake-up.

Fig. 3 :Fig. 4 :

 34 Fig. 3: BER as a function of E b /N 0 .

Fig. 5 :

 5 Fig. 5: Average power consumption per successful packet.

TABLE I :

 I Minimum energy coding mapping table.

	Source symbol (k)	Mapped symbol (n = 2 k -1)
	00..00	0000..000
	00..01	0000..001
	...	...
	...	...
	...	...
	11..10	0100..000
	11..11	1000..000

This work is part of the project Wake-Up funded by the French National Research Agency (ANR).


Abdelaziz Jouaiti
email: jouaiti@unistra.fr

Terpyridinebenzaldehyde isomers: One-pot facile synthesis

Keywords: One-pot, Terpyridine, (Diethoxymethyl)benzaldehyde, Terpyridinebenzaldehyde

 terpyridin]-4 ′ -yl)benzaldehyde isomers (para, meta and ortho position). These compounds have been synthesized in one-pot conditions using ethanol and aqueous ammonia as solvents, at room temperature. This methodology offers substantial advantages with respect to its simplicity of operation, reaction time, satisfying yield of products and easy work-up procedure under mild reaction conditions. Apart from spectroscopic characterization, the structure of one of the Terpyridinebenzaldehyde derivative is confirmed by single-crystal X-ray diffraction.

Introduction

Supramolecular chemistry, in particular the self-assembly of functional structures in metallosupramolecular architectures based on the use of transition metals and suitable ligands, has been a very active area of research in the recent decades. [START_REF] Chen | Chiral metallosupramolecular architectures[END_REF][START_REF] Wu | Construction of supramolecular hexagonal metallacycles via coordination-driven self-assembly: Structure, properties and application[END_REF][START_REF] Gan | Preparation and Post-Assembly Modification of Metallosupramolecular Assemblies from Poly(N-Heterocyclic Carbene) Ligands[END_REF]. The use of functionalized "metallaligands" as "molecular bricks" is a simple way to form sophisticated molecular architectures, based on weak interactions such as hydrogen or covalent bonds like with imines. In this context, 2,2';6',2"-terpyridine and its functionalized derivatives have been widely used in the field of coordination and supramolecular chemistry to form "metallaligand", for example. [START_REF] Housecroft | The terpyridine isomer game: from chelate to coordination network building block[END_REF]. Their remarkably high binding affinity towards most transition-metal ions and their chelation properties make terpyridine derivatives highly attractive building blocks for the construction of complex metallosupramolecular systems [5-10]. Coordination complexes with functionalized terpyridines are used in catalysis, [START_REF] Zhang | 1-D manganese(ii)-terpyridine coordination polymers as precatalysts for hydrofunctionalisation of carbonyl compounds[END_REF][START_REF] Kwong | New chiral 2,2′:6′,2″-terpyridine ligands from the chiral pool: synthesis, crystal structure of a rhodium complex and uses in copper-and rhodium-catalyzed enantioselective cyclopropanation of styrene[END_REF][START_REF] Zhang | Immobilization of Ru(terpyridine)(2,6-pyridinedicarboxylate) onto MCM-41 and its catalysis in the oxidation of alcohols[END_REF] photochemistry, [START_REF] Schofield | Photochemical and thermal ligand exchange in a ruthenium(ii) complex based on a scorpionate terpyridineligand[END_REF][START_REF] Labra-Vázquez | Chemical and photochemical behavior of ruthenium nitrosyl complexes with terpyridine ligands in aqueous media[END_REF][START_REF] Jang | The synthesis and optical characterization of quinoxalines bearing 2,2′:6′,2″-terpyridine[END_REF] medical chemistry [START_REF] Rajalakshmi | Copper(II) complexes of terpyridine derivatives: A footstep towards development of antiproliferative agent for breast cancer[END_REF][START_REF] Liang | Synthesis, characterization, photoluminescence, anti-tumor activity, DFT calculations and molecular docking with proteins of zinc(ii) halogen substituted terpyridine compounds[END_REF][START_REF] Hahn | Functionalization of Ruthenium(II) Terpyridine Complexes with Cyclic RGD Peptides To Target Integrin Receptors in Cancer Cells[END_REF] and dye sensitized solar cells. [START_REF] Robson | Design and Development of Functionalized Cyclometalated Ruthenium Chromophores for Light-Harvesting Applications[END_REF][START_REF] Ozawa | Highly efficient dye-sensitized solar cells based on a ruthenium sensitizer bearing a hexylthiophene modified terpyridine ligand[END_REF][START_REF] Caramori | Combination of Cobalt and Iron Polypyridine Complexes for Improving the Charge Separation and Collection in Ru(terpyridine)2-Sensitised Solar Cells[END_REF][START_REF] Duchanois | An Iron-Based Photosensitizer with Extended Excited-State Lifetime: Photophysical and Photovoltaic Properties[END_REF][START_REF] Ozawa | Efficient Ruthenium Sensitizer with an Extended π-Conjugated Terpyridine Ligand for Dye-Sensitized Solar Cells[END_REF] Along this line, it seems interesting to develop an easy synthesis for such terpyridine derivatives. Thus, we became interested in aldehydes because they are versatile reagents in organic synthesis and, especially aromatic aldehydes, have been extensively used as starting reagents for various imine reactions to synthesize supramolecular architectures. [START_REF] Qian | Toward Covalent Organic Frameworks Bearing Three Different Kinds of Pores: The Strategy for Construction and COF-to-COF Transformation via Heterogeneous Linker Exchange[END_REF][START_REF] Mastalerz | Porous Shape-Persistent Organic Cage Compounds of Different Size, Geometry, and Function[END_REF][START_REF] Greenaway | High-throughput discovery of organic cages and catenanes using computational screening fused with robotic synthesis[END_REF][START_REF] Chen | Towards covalent organic frameworks with predesignable and aligned open docking sites[END_REF] These efforts led to the development of a synthetic method for ligands of the terpyridine family, L1, L2 and L3, bearing benzaldehyde derivative groups (Figure 1). In the literature, two types of synthetic strategies have been reported for the synthesis of 4 -([2,2 ′ :6 ′ ,2 ″ -terpyridin]-4 ′ -yl)benzaldehyde L1 and one for 3-([2, 2′ :6′, 2″-terpyridin]-4′-yl)benzaldehyde L2. First, L1 has been prepared in four steps (Scheme 1, (a)). [START_REF] Goodall | The synthesis of 4′-aryl substituted terpyridines by Suzuki crosscoupling reactions: substituent effects on ligand fluorescence[END_REF] The last step reaction of this pathway is based on the palladium-catalysed cross-coupling of 4' -triflate-terpyridine with 4-formylphenylboronic acids, with an overall yield of 6%. The second synthetic approach for L1 [START_REF] Miyamoto | Synthesis and Photochemical Properties of a Photochromic Iron(II) Complex of Hexaarylbiimidazole[END_REF] (Scheme 1, (b)) is based, in the first step, on the preparation of 4'-tolyl-2,2':6',2"-terpyridine followed by bromination and finally oxidation, with an overall yield of 17% yield. Concerning L2, one synthetic strategy has been recently described. [START_REF] Filosa | Order from Chaos: Self-Assembly of Nanoprism from a Mixture of Tetratopic Terpyridine-Porphyrin Conformers[END_REF]. This product was synthesized in three steps from isophalaldehyde with an overall yield of almost 20% (Scheme 1 (c)).

Nevertheless, there are certain limitations to these three methods: too long synthesis time, the use of expensive reagents and toxic solvents. In addition to all these drawbacks, the overall yields of these three methods is low: 6%, 17% and 20% respectively.

The development of an efficient and general approach for obtaining 4-([2, 2′ :6′, 2″-terpyridin]-4′-yl)benzaldehyde L1 or terpyridinebenzaldehyde isomers, 3-([2, 2′ :6′, 2″-terpyridin]-4′-yl)benzaldehyde L2 and the positional isomer 2-([2, 2′ :6′, 2″-terpyridin]-4′-yl)benzaldehyde L3, under metal-free conditions using a one-pot synthesis, is of overriding value and challenging. Therefore, an efficient protocol should using straightforward and readily available starting components, appears really appealing.

Herein, we report an efficient and easy method to obtain terpyridinePh-CHO (-CHO in para, meta or ortho position (L1, L2 or L3)). Indeed, these compounds have been synthesized in one-pot reactions under metal-free conditions using ethanol and water as solvents. This procedure features short reaction times, easy work-up, and good yields. Most of used starting materials are commercially available and non-expensive.

Results and discussion

The first known synthesis for terpyridine derivatives is the one reported by Kröhnke et al. in 1976, [START_REF] Kröhnke | The Specific Synthesis of Pyridines and Oligopyridines[END_REF] followed by other methods such as the use of the Stille coupling, for example. [START_REF] Heller | Functionalized 2,2'-bipyridines and 2,2':6',2' '-terpyridines via stille-type crosscoupling procedures[END_REF]. But the recently reported synthetic methods [START_REF] Cave | Toward benign syntheses of pyridines involving sequential solvent free aldol and Michael addition reactions[END_REF][START_REF] Wang | A Facile Route to Sterically Hindered and Non-Hindered 4′-Aryl-2,2′:6′,2′′-Terpyridines[END_REF][START_REF] Rocco | Synthesis of Terpyridines: Simple Reactions-What Could Possibly Go Wrong?[END_REF] marked a significant improvement. Indeed, the functionalized terpyridines were easily obtained via a condensation sequence of aldol and Michael addition, involving the use of solid NaOH, followed by treatment with ammonium acetate or aqueous ammonia in a one-pot reaction, with high yield. Our strategy for obtaining L1, L2 or L3 is based on the adaptation of an already reported method of this synthesis, that leads to terpyridinebenzaldehyde isomers. The electrophilic nature of the carbonyl group of these compounds is a dominant feature of its possible extensive chemistry that is occurring. Here, in order to synthesize these compounds, we need a starting material containing two carbonyl groups.

It is therefore necessary to protect one carbonyl that we would like to find at the end of synthesis, from a nucleophilic attack. The use of readily available (diethoxymethyl) benzaldehyde seems perfectly suitable, since one carbonyl will undergo a nucleophilic attack to synthesize the terpyridine moiety while the other carbonyl is protected against this attack. [START_REF] Achelle | Photophysics and Nonlinear Optical Properties of Stilbenoid Pyrimidine-Based Dyes Bearing Methylenepyran Donor Groups[END_REF] This proposed strategy allows to generate the carbonyl at the end of the reaction and therefore to have access to benzaldehyde moiety. A mild and easy regeneration of the carbonyl compounds from their resulting 1,1-diacetals has been carried out. Indeed, these acetals easily undergo deacetalization to yield terpyridinebenzaldehyde isomers, under acidic conditions at room temperature.

The proposed synthetic pathways, for the synthesis of L1, L2 and L3, considering this strategy, are presented in Scheme 1 (d) and Scheme 2. The required starting compounds, 3 and 4-(diethoxymethyl)benzaldehyde isomers, are commercially available. The 2-(diethoxymethyl)benzaldehyde is easily prepared by lithiation of commercially available 2-bromo-(diethoxymethyl)benzene with n-BuLi at -70 °C and subsequent treatment with DMF, as described in the literature. [START_REF] Chezal | Synthesis of carbamoylpyridine and imidazo[1,5-a]pyridin-1,3-diones via ortho-acetalhydantoin intermediates[END_REF][START_REF] Ueda | Efficient Entry into 2-Substituted Tetrahydroquinoline Systems through Alkylative Ring Expansion: Stereoselective Formal Synthesis of (±)-Martinellic Acid[END_REF] For the synthesis of L1, L2 and L3, we adopted two strategies: the first one, (Scheme 2), is based on separating the diacetalterpyridine derivatives as intermediate products before reaching the targeted products. The second strategy (Scheme 1 (d)) is under one-pot conditions.

The two-step synthesis (Scheme 2 see ESI for experimental details) of the terpyridinebenzaldehyde isomers begins by mixing 2-acetylpyridine and different (diethoxymethyl)benzaldehyde precursors in ethanol in 2:1 molar ratio in the presence of KOH pellets and NH3 aqueous solution. The reaction is completed by stirring the mixture at room temperature overnight. After reducing the volume, the mixture is extracted with ethyl acetate and purified by short column chromatography affording the desired (diethoxymethyl)benzaldehyde derivatives 1, 2 and 3 in 86%, 83% and 50% respectively. In the second step, a dilute HCl solution is added to deprotect the aldehyde; neutralizing the medium allows to obtain the desired aldehyde products L1, L2 and L3 in 91%, 86% and 73% yield respectively. Scheme 2. : Two steps synthetic pathway for the obtention of L1, L2 and L3

The one-pot approach (Scheme 1 (d)) is based on the use of the reactivity profile in the basic medium of protected benzaldehydes, in order to achieve the targeted products. (Diethoxymethyl)benzaldehyde (para, meta or ortho) is added to 2-acetylpyridine in ethanol in 2:1 molar ratio (see ESI for experimental details), in the presence of KOH pellets and NH3 aqueous solution. To the mixture, a dilute HCl solution is added, neutralizing the medium and allowing us to obtain the desired aldehyde products L1, L2 and L3 in 76%, 69% and 43% yield respectively. The yield of the two synthesis methods are slightly similar (see In addition to their spectroscopic data (see ESI for characterization details), the structure of L3 has been confirmed by single crystal X-ray diffraction studies in the solid state (Figure 2). Single crystals suitable for X-ray diffraction analysis

Conclusions

The use of (diethoxymethyl)benzaldehyde as a readily available starting material allowed us to obtain three terpyridinebenzaldehyde isomer derivatives. This methodology offers substantial advantages with respect to its simplicity of operation, availability of starting materials, reaction times, yield of products and easy work-up procedure under mild reaction conditions. These significant features are expected to contribute to the development of a green strategy for the synthesis of new terpyridinebenzaldehyde derivatives and subsequently to novel metallosupramolecular architectures.

Experimental section a) General method for the synthesis of the Terpyridinebenzaldehyde isomer L1.

To a solution of 2-Acetylpyridine (1.16 g, 9.5 mmol), potassium hydroxide (0.54g, 9.6 mmol) and the corresponding (Diethoxymethyl)benzaldehyde in 10mL of absolute ethanol (1g,4.8 mmol), were added 12 mL of 32 % aqueous ammonia solution. The mixture was stirred overnight at room temperature. The reaction volume was reduced by half, then 15 ml of a 15% aqueous HCl solution were added. After 3h at room temperature, the solution was neutralized by a 10% aqueous K2CO3 solution. The mixture was extracted with dichloromethane (3x 30 mL). The combined organic layer was dried with Na2SO4, filtered and the solvent was removed under reduced pressure. The aldehyde phenyl-Terpyridne derivatives L1

was obtained as a white solid by washing the crude product with methanol in 76% yield. If necessary, the crude product was purified by a short column chromatography (Al2O3, eluant, ethyl acetate/cyclohexane 1:1). Note, to make a pure product, it's necessary to wash with MeOH.

Compound L1: white solid, 1.2g, 76% yield, mp = 195°C.

Figure 1 :

 1 Figure 1: Terpyridinebenzaldehyde derivatives L1, L2 and L3

Scheme 1 .

 1 Scheme 1. : Conventional Methods : (a) and (b) reported for the preparation of 4-([2,2 ′ :6 ′ ,2 ″ -terpyridin]-4 ′ -yl)benzaldehyde; (c) for the preparation of 3-([2,2 ′ :6 ′ ,2 ″ -terpyridin]-4 ′ -yl)benzaldehyde; (d) the one-pot strategy developed herein (this work).

  have been obtained for L3, so far by slow evaporation of a CHCl3/EtOH solution at room temperature (see the ESI for crystallographic data, CCDC 2018232 (L3)). The compound crystallizes in the monoclinic space group, P 21/n. The C = C, C -C, C-N, C = N and C = O distances are within the expected range for this type of covalent bonds (d =1.208 -1.493 Å).The three pyridine groups are almost coplanar. The benzaldehyde group is not coplanar with the central pyridine, but tilted by -46.87°.

Figure 2 :

 2 Figure 2: Single crystal X-ray structure of L3. Hydrogen atoms are omitted for the sake of clarity.

Table below

 below

	)
		L1	L2	L3
	Isolated yield (%) :	78%,	71%	36%
	two step synthesis method
	Isolated yield (%) :	76%,	69%	43%
	one-pot synthesis method

Table :

 : Comparison of the results of both synthetic methods.

  CDCl3, 75 MHz): δ (ppm) = 191.9, 156.0, 155.7, 149.0, 148.9, 144.4, 137.1, 136.4, 130.3, 128.1, 124.1, 121.5, Elemental analysis (%) for C22H15N3O, calculated: C, 78.32; H, 4.48; N, 12.46; found: C, 78.36; H, 4.54; N, 12.40.Full experiment details, characterization data ( 1 H NMR,[START_REF] Zhang | Immobilization of Ru(terpyridine)(2,6-pyridinedicarboxylate) onto MCM-41 and its catalysis in the oxidation of alcohols[END_REF] C NMR spectra and elemental analysis) and copies of 1 H NMR and[START_REF] Zhang | Immobilization of Ru(terpyridine)(2,6-pyridinedicarboxylate) onto MCM-41 and its catalysis in the oxidation of alcohols[END_REF] C NMR spectra are included in the Supplementary material. CIF data of compound (L3) is deposited in Cambridge Crystallographic Data CentreCenter (CCDC) and its CCDC number: 2018232. The data is available free of charge at http://www.ccdc.cam.ac.uk.

	1 H-NMR (CDCl3, 300 MHz): δ (ppm) = 7.37 (ddd, j1=1.5Hz, j2=5Hz, j3=7.5Hz, 2 H), 7.89 (td, j=7.5Hz, 1 H), 8.04 (m, 4H), 8.68
	(d, j1=8.1Hz, 2H), 8.74 (m, 2 H), 8.77 (s, 2 H), 10.10 (s, 1 H).
	119.1

13 C-NMR (

Acknowledgments

Thanks to N. Kyritsakas for the structural analysis Prof. S. Ferlay and S. Baudron for proofreading. The Université de Strasbourg and CNRS are acknowledged for financial support.