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A collection of cobalt polypyridine complexes employed for the light-driven HER in aqueous solution is presented with the aim of highlighting the relevant chemical motifs that play a role in supporting efficient catalytic activity.

International audience; Cobalt(II) complexes featuring hexadentate amino-pyridyl ligands have been recently discovered as highly active catalysts for the Hydrogen Evolution Reaction (HER), whose high performance arises from the possibility to assist proton transfer processes via intramolecular routes involving detached pyridine units. With the aim of gaining insights in such catalytic routine, three new proton reduction catalysts based on amino-polypyridyl ligands are reported, focusing on substitution of the pyridine ortho- position. Especially, a carboxylate (C2) and two hydroxyl substituted pyridyl moieties (C3, C4) are introduced with the aim of promoting intramolecular proton transfer possibly enhancing the efficiency of the catalysts. Foot-of-the-wave and catalytic Tafel plot analyses have been utilized to benchmark the catalytic performances under electrochemical conditions in acetonitrile using trifluoroacetic acid as the proton source. In this respect, the cobalt complex C3 results as the fastest catalyst in the series, maximum turnover frequency (TOF) of 1.6 (± 0.5)x105 s-1, but at the expenses of large overpotentials. Mechanistic investigation by means of Density Functional Theory (DFT) suggest a typical ECEC mechanism (i.e. a sequence of reductions -E- and protonations -C- events) for all the catalysts, as previously envisioned for the parent unsubstituted complex C1. Interestingly, in the case of complexes C2, the catalytic route is triggered by initial protonation of the carboxylate group resulting in a less common (C)ECEC mechanism. The pivotal role of the hexadentate chelating ligand in providing internal proton relays to assist hydrogen elimination is further confirmed within this novel class of molecular catalysts, thus highlighting the relevance of a flexible polypyridine ligand in the design of efficient cobalt complexes for the HER. Photochemical studies in aqueous solution using [Ru(bpy)3]2+ (where bpy = 2,2’-bipyridine) as the sensitizer and ascorbate as the sacrificial electron donor support the superior performance of C3.

Luminescent Ir(C^N)

This paper reports on the development of a fluorescent label-free aptamer assay integrated in a lab-on-chip (LoC) system for the detection of Ochratoxin A (OTA). The detection system relies on the integration, on a single glass substrate, of an array of amorphous silicon photosensors and a long pass interferential filter. The aptamer assay, integrated into the microfluidic network, is an aptasensor having affinity versus OTA, selected as a case study. The fluorescent molecule is a "light switch" complex [Ru(phen)

Four novel polypyridine cobalt(II) complexes were developed based on a hexadentate ligand scaffold bearing either electron-withdrawing (-CF3 ) or electron-donating (-OCH3 ) groups in different positions of the ligand. Experiments and theoretical calculations were combined to perform a systematic investigation of the effect of the ligand modification on the hydrogen evolution reaction. The results indicated that the position, rather than the type of substituent, was the dominating factor in promoting catalysis. The best performances were observed upon introduction of substituents on the pyridine moiety of the hexadentate ligand, which promoted the formation of the Co(II)H intermediate via intramolecular proton transfer reactions with low activation energy. Quantum yields of 11.3 and 10.1 %, maximum turnover frequencies of 86.1 and 76.6 min-1 , and maximum turnover numbers of 5520 and 4043 were obtained, respectively, with a -OCH3 and a -CF3 substituent.

This paper presents the development of a lab-on-chip, based on thin-film sensors, suitable for DNA treatments. In particular, the system performs on-chip DNA amplification and separation of double-strand DNA into single-strand DNA, combining a polydimethylsiloxane microfluidic network, thin-film electronic devices, and surface chemistry. Both the analytical procedures rely on the integration on the same glass substrate of thin-film metal heaters and amorphous silicon temperature sensors to achieve a uniform temperature distribution (within ±1 °C) in the heated area and a precise temperature control (within ±0.5 °C). The DNA separation also counts on the binding between biotinylated dsDNA and a layer of streptavidin immobilized into a microfluidic channel through polymer-brushes-based layer. This approach results in a fast and low reagents consumption system. The tested DNA treatments can be applied for carrying out the on-chip systematic evolution of ligands by exponential enrichment process, a chemistry technique for the selection of aptamers.

New functional coordination polymers based on the semi-flexible 9,10-di(1H-imidazol-1-yl)-anthracene ligand (L) with ZnII and CdII, namely {[Zn(μ2-L)2](ClO4)2·m(MeOH)·n(DCM)}n (1), {[Zn(μ2-L)2](BF4)2·m(MeOH)·n(DCM)}n (2), {[Zn(μ2-L)2(p-Tos)2]·m(DCM)·n(MeOH)}n (3), {[Cd(μ2-L)2(p-Tos)2]·m(DCM)}n (4) {[Cd(μ2-L)2(p-Tos)2]·m(MeOH)·n(Dioxane)}n (5) and {[Zn(μ2-L)2(CF3CO2)2]·2(Dioxane)}n (6), were obtained. Dissolving L in polar solvent mixtures MeOH–DCM (4 : 1) or MeOH–dioxane (1 : 1) with ZnII and CdII salts resulted in the formation of complexes 1, 2, and 5 adopting a cis-conformation of the imidazole groups with respect to anthracene. In less polar mixtures of solvents such as MeOH–DCM (1 : 4) trans-L is observed, leading to the coordination polymers 3–4 with ZnII and CdII. In an intermediate solvent mixture such as MeOH–dioxane (1 : 4), the cis- and trans-conformation coexist as exemplified in complex 6 with ZnII. In the solid state, complexes 1–5 assemble as supramolecular 2-D coordination polymers with a (4,4) topology, while 6 forms a tridimensional porous network with a cds topology. All compounds reveal strong blue emission in the solid state at room temperature.

Heterotelechelic polymers were synthesized by a kinetic telechelic ring-opening metathesis polymerization method relying on the regioselective cross-metathesis of the propagating Grubbs' first-generation catalyst with cinnamyl alcohol derivatives. This procedure allowed the synthesis of hetero-bis-end-functional polymers in a one-pot setup. The molecular weight of the polymers could be controlled by varying the ratio between cinnamyl alcohol derivatives and monomer. The end functional groups can be changed using different aromatically substituted cinnamyl alcohol derivatives. Different monomers were investigated and the presence of the functional groups was shown by NMR spectroscopy and MALDI-ToF mass spectrometry. Labeling experiments with dyes were conducted to demonstrate the orthogonal addressability of both chain ends of the heterotelechelic polymers obtained.

The first heptacoordinate cobalt catalyst for light-driven hydrogen production in water has been synthesized and characterized. Photochemical experiments using [Ru(bpy)3]2+ as photosensitizer gave a turnover number (TON) of 16300 mol H2 (mol cat.)−1 achieved in 2 hours of irradiation with visible (475 nm) light. This promising result provides a path forward in the development of new structures to improve the efficiency of the catalysis.

International audience; H2 evolution catalyzed by a heptacoordinate complex under both electro- (1) and photo-chemical (2) conditions is analyzed in detail in order to gain insights into the mechanism of the processes. The complex shows high catalytic activity for hydrogen production in acetonitrile, in the presence of trifluoroacetic acid and triethylammonium tetrafluoroborate as proton sources. Foot-of-the-wave analysis (FOWA) and Tafel plot analysis have been applied to elucidate the kinetics of the hydrogen evolution mechanism and to benchmark the catalytic performances, respectively, with remarkably high rates being obtained at the expense of high overpotentials. Transient absorption spectroscopy measurements have been performed to characterize the kinetics and relevant intermediates formed under photocatalytic conditions. A computational investigation, based on density functional theory (DFT) and time-dependent DFT (TD-DFT), has also been carried out to characterize the intermediate species and support the experimental results. A combination of both experimental and theoretical data suggests the formation of catalytic intermediates displaying dangling pyridine groups in both the one- and two-electron reduced species, possibly acting as proton-transfer relays to enable efficient H–H bond formation.

Tetraarylethenes are obtained by acid‐induced coupling of vinyl triazenes with aromatic compounds. This new C−H activation route for the synthesis of aggregation‐ induced emission luminogens is simple, fast, and versatile. It allows the direct grafting of triarylethenyl groups onto a variety of aromatic compounds, including heterocycles, supramolecular hosts, biologically relevant molecules, and commercial polymers.

Highly substituted Δ

Enyne ring closing metathesis has been used to synthesize functional group carrying metathesis catalysts from a commercial (Ru-benzylidene) Grubbs’ catalysts. The new Grubbs-type ruthenium carbene was used to synthesize living heterotelechelic ROMP polymers without any intermediate purification. Olefin metathesis with a mono substituted alkyne followed by ring closing metathesis with an allylic ether provided efficient access to new functional group carrying metathesis catalysts. Different functional benzylidene and alkylidene derivatives have been investigated in the synthesis of heterotelechelic polymers in one pot.

The synthesis and photodecomposition behaviour of a family of CO releasing molecules (CORMs) based on [Mn(CO)3bpy] derivatives connected to a semiconductor Quantum Dot (QD) sensitizer is described here. Compared to the non-sensitized complexes, such systems show a 2 to 6-fold increase of the photodecomposition rate upon irradiation with visible light.

General discussion on natural and artificial photosynthesis.

New functional coordination polymers based on the semi-flexible 9,10-di(1H-imidazol-1-yl)-anthracene ligand (L) with Zn

Heterotelechelic polymers were synthesized by a kinetic telechelic ring‐opening metathesis polymerization method relying on the regioselective cross‐metathesis of the propagating Grubbs’ first‐generation catalyst with cinnamyl alcohol derivatives. This procedure allowed the synthesis of hetero‐bis‐end‐functional polymers in a one‐pot setup. The molecular weight of the polymers could be controlled by varying the ratio between cinnamyl alcohol derivatives and monomer. The end functional groups can be changed using different aromatically substituted cinnamyl alcohol derivatives. Different monomers were investigated and the presence of the functional groups was shown by NMR spectroscopy and MALDI‐ToF mass spectrometry. Labeling experiments with dyes were conducted to demonstrate the orthogonal addressability of both chain ends of the heterotelechelic polymers obtained.

The first heptacoordinate cobalt catalyst for light-driven hydrogen production in water has been synthesized and characterized. Photochemical experiments using [Ru(bpy)

The realization of CO releasing molecules triggered by light (photoCORMs) within the phototherapeutic window (λ > 600 nm) constitutes an important goal for potential therapeutic applications of the molecules. The activation of photoCORMs with red/NIR light would enable exploiting the higher depth of penetration of this radiation with respect to higher energy photons. In this article we report a family of carbonyl Mn(I) complexes capable of releasing CO when triggered with red light (≥625 nm). Such complexes are based on 2,2′-azopyridine ligands modified by the introduction of electron-donating or electron-withdrawing substituents. Our results indicate that electron deficient ligands induce a gradual decrease of the HOMO−1/LUMO gap of the species (i.e. of the orbitals involved in the lowest energy transition), thus enabling a fine tuning of their visible absorption maxima between 630 and 693 nm. The synthesis of the complexes and their photodecomposition behaviour towards CO release are described. We suggest that this approach could be generalized for further development of low-energy activated photoCORMs.

Anthracene derivatives of ruthenium(II) arene compounds with 1,3,5-triaza-7-phosphatricyclo[3.3.1.1]decane (pta) or a sugar phosphite ligand, viz., 3,5,6-bicyclophosphite-1,2-O-isopropylidene-α-d-glucofuranoside, were prepared in order to evaluate their anticancer properties compared to the parent compounds and to use them as models for intracellular visualization by fluorescence microscopy. Similar IC(50) values were obtained in cell proliferation assays, and similar levels of uptake and accumulation were also established. The X-ray structure of [{Ru(η(6)-C(6)H(5)CH(2)NHCO-anthracene)Cl(2)(pta)] is also reported.

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Proposals for systems embodying condensed matter spin qubits cover a very wide range of length scales, from atomic defects in semiconductors all the way to micron-sized lithographically-defined structures. Intermediate scale molecular components exhibit advantages of both limits: like atomic defects, large numbers of identical components can be fabricated; as for lithographically defined structures, each component can be tailored to optimize properties such as quantum coherence. Here, we demonstrate what is perhaps the most potent advantage of molecular spin qubits, the scalability of quantum information processing structures using bottom-up chemical self-assembly. Using Cr7Ni spin qubit building blocks, we have constructed several families of two-qubit molecular structures with a range of linking strategies. For each family, long coherence times are preserved, and we demonstrate control over the inter-qubit quantum interactions that can be used to mediate two-qubit quantum gates., Manuscript: 20 pages. Supplementary Information: 16 pages. npj Quantum Information, in press

Constitutional isomers of cyanocobalamin adducts based on a fluorescent rhenium tris-carbonyl diimine complex were prepared, characterized and tested against PC-3 cancer cells. The adducts differ only in the relative binding position of the organometallic species which is either bound at the cyano or the 5′-hydroxo group of vitamin B₁₂. When tested for their cytotoxic potency, the species showed IC₅₀ values in the low μM rage. Upon conjugation to the vitamin an energy transfer process causes an extremely low quantum yield of fluorescence emission, making the conjugates unsuitable for fluorescence imaging. However, by exploiting the vibrational signature of the fac-[Re(CO)₃]⁺ core, their cellular distribution was evaluated via FTIR spectromicroscopy.

We here report the synthesis and structural characterization of the first iridium(III) complex with a caged ligand structure, which shows a 80% decrease of oxygen quenching compared to the archetypical Ir(ppy)(3).

Lower cyclic oligomers C2–C5 of a family of naphthalenophane formaldehyde acetals Cn have been isolated and characterized, the dimer being obtained in two atropisomeric forms, syn-C2 and anti-C2, as confirmed by X-ray analysis. The investigated cyclophanes showed interesting recognition properties towards electron-poor guests (K≈105 M−1 for association of the guanidinium ion with C3 in chloroform). A library of macrocycles was generated by acid catalyzed transacetalation of Cn in chloroform, but the dynamic nature of the system was spoiled by the occurrence of irreversible reaction pathways promoted by the relatively easy formation of extended benzyl-like carbocations I.

Large macrocycles containing imine and borasiloxane links are obtained in polycondensation reactions of 4-formylbenzeneboronic acid, t-Bu(2)Si(OH)(2), and diamines. The multicomponent reactions can be performed in solution or--advantageously--by mechanochemical syntheses in a ball mill.

A series of nine luminescent cyclometalated octahedral iridium(III) tris(2-phenylpyridine) complexes has been synthesized, functionalized with three different amino acids (glycine, alanine, and lysine), on one, two, or all three of the phenylpyridine ligands. All starting complexes and final compounds have been fully analyzed by one-dimensional (1D) and two-dimensional (2D) NMR spectroscopy, and photophysical data have been obtained for all the mono-, bis-, and tri- substituted iridium(III) complexes. Cellular uptake and localization have been studied with flow cytometry and confocal microscopy, respectively. Confocal experiments demonstrate that all nine substituted iridium(III) complexes show variable uptake in the tumor cells. The monosubstituted iridium(III) complexes give the highest cellular uptake, and the series substituted with lysines shows the highest toxicity. This systematic study of amino acid-functionalized Ir(ppy)(3) complexes provides guidelines for further functionalization and possible implementation of luminescent iridium complexes, for example, in (automated) peptide synthesis or biomarker specific targeting.

The synthesis, structural, photophysical, theoretical, and electrochemical characterization of four tris(2-phenylpyridine)-based IrIII complexes are reported. The complexes were functionalized on the pyridine or on the phenyl rings with amide moieties substituted with a tris(ethyl)amine or ethyl groups, thereby yielding a family of compounds with hemicaged or open (without a capping unit but with similar functional groups on the ligand) structure. Within the context of the parent tris(2-phenylpyridine) and the full-cage iridium(III) complexes, structure–photoluminescence quenching relationships (SPQR) of the four complexes have been investigated. Luminescence quenching by oxygen has been studied with Stern–Volmer plots and through evaluation of the thermodynamic parameters involved in the quenching process. Density functional theory (DFT) and time-dependent DFT (TD-DFT) calculations have been performed on the complexes to gain insights into structural and electronicfeatures and the nature of the excited states involved in the electronic absorption processes. Interestingly, shielding by the capping unit of moieties in which the LUMO orbital is mostly localized (on the pyridines) results in a dramatic 40 % decrease in oxygen quenching. Conversely, shielding ofmoieties in which the HOMO orbital is partially localized (on the phenyl rings) does not induce any change in the oxygen quenching degree. In both sets of compounds, the thermodynamic feasibility of oxygen quenching is the same for the hemicaged and open compounds, thus giving evidence of the structural origin of such quenching decrease. The SPQRopens up new routes to the design of tailored, more or less sensitive to oxygen, luminescent iridium complexes (e.g., for use as biolabels).

Luminescent transition metal complexes are enjoying a growing interest because of their ubiquitous applications in, e.g., the fields of material science, sensors and (biomedical) diagnostics, and iridium(III) and ruthenium(II) complexes are among the best studied. Due to their long-living excited states, these complexes can have a strong interaction with dioxygen, resulting in luminescence quenching. This oxygen quenching might be regarded as an unwanted effect in luminescence imaging, but, on the other hand, it can be exploited for diagnostic and therapeutic applications as well. After a theoretical introduction concerning the dioxygen quenching mechanism and the parameters involved, in the second part of this review we focus on the possibility of tailoring this quenching by modifying selected properties of a complex (triplet energy, oxidation potential, localization and shielding of the excited state) in order to obtain systems with higher or lower oxygen quenching compared to the archetypical complexes. In the third part of this review an overview of the applications of oxygen quenching of luminescence is offered, with particular attention to biomedical use: diagnostic oxygen sensing, imaging and therapy.

The design of luminophores with high brightness is of crucial importance for many applications like the realization of Organic Light Emitting Diodes (OLEDs), and for biomedical imaging. However, despite the great number of works dedicated to the definition of the possible strategies for the realization of bright compounds, we are still far from a "perfect" luminophore for biological applications. The design of highly bright luminophores for biological imaging still constitutes a major challenge: the necessity of conjugating a high brightness (the product of the quantum yield and the molar extinction coefficient) with a low degree of oxygen quenching (which is necessary in order to keep a high luminescence in the oxygen-rich bio-environment) is still an open problem. Semiconductor Quantum Dots (QDs) are so far, the best candidates for biological applications since they show quantum yields closed to the unity and low oxygen sensitivity. However, despite the brilliant performances shown by QDs, their in vivo toxicity is still a major concern, especially from the perspective of a human application. Transition metal complexes are ideal candidates for the realization of bright luminophores, considering their high stability in biological environment and the possibility of tuning their optical properties by conveniently changing the structure of the ligands. Ruthenium(II) and iridium(III) complexes, in particular, are among the most studied transition metal complexes and the large amount of literature available makes them ideal candidates for further improvement. Two possible strategies can be followed in order to improve the optical properties of a luminophore: the decrease of its oxygen quenching degree and the amplification of its brightness. The first strategy is quite promising especially in order to improve the optical properties of Ir(III)-complexes, which show a pronounced oxygen sensitivity. Conversely, the brightness amplification via multiple labelling is particularly attractive for Ru(II)-complexes, which are barely sensitive to oxygen quenching but show also a low emission quantum yield. In this thesis both strategies have been applied in order to realise highly bright luminescent compounds based on Ru(II) or Ir(III) complexes. Moreover, since there is only a limited amount of literature concerning the tunability of the oxygen quenching of Ir(III)-complexes, a systematic study has been conducted in order to clarify the structure-quenching relationship.

The photophysical properties of two atropisomeric naphthalenophanes (1 and 2) have been studied. Their structure only differs in the relative arrangement, syn (1) or anti (2), of the two aromatic units. The compounds emission is mainly excimeric and is strongly quenched in the presence of oxygen. Comparison of emission intensities obtained from steady state and from decay times provides clear evidence of the formation of ground state charge transfer complexes between oxygen and the naphthalenophanes 1 and 2. The calculated values for the association constants are on the order of 10(3) M(-1) (ethanol, room temperature) for both naphthalenophanes.

The screening of molecular targets benefits from design criteria, which can identify the most promising candidates. We demonstrate that π-depleted polyaromatic molecules present superior π-stacking ability. This realization is quantified using a computational criterion, LOLIPOP, that detects ideal π-conjugated frameworks. The utility of LOLIPOP is illustrated by identifying tailored chemosensors.

The dye disodium 3,4:3',4'-bibenzo[b]thiophene-2,2'-disulfonate can be used as a molecular probe for the fluorimetric detection of caffeine in aqueous solution. The fluorescence response is attributed to non-covalent interactions of caffeine with the dye in the ground state and in the excited state. The bimodal interaction allows performing ratiometric measurements with very good selectivity over structurally related analytes. The dye was also used to develop a simple test strip for the visual differentiation of normal and decaffeinated coffee with a standard UV lamp.

Boronic acid-capped clathrochelates were used to build rigid, linear bipyridyl ligands with adjustable lengths between 1.5 and 5.4 nm. The syntheses can be accomplished in one or two steps from simple starting materials. The potential of these ligands as building blocks for metallasupramolecular chemistry is unveiled through the preparation of a discrete metallamacrocyclic structure and a heterometallic coordination polymer.

The aggregation-induced emission properties of tetraarylethenes (TAEs) have led to numerous applications in chemistry, biology, and materials science. Herein, we describe two fluorinated tetraarylethenes, which can be employed as universal tags for the synthesis of solid state luminogens. The tags are accessible in one or two steps from commercially available starting materials. Facile coupling reactions with ubiquitous substrates such as thiols, alcohols, amines, phosphines, aldehydes, and enamines allow preparing a wide range of TAE conjugates, including tagged amino acids, peptides, carbohydrates, steroids, and commercial polymers.