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International audience; We propose here a new method to functionalize carbon materials via a catalyzed Diels–Alder reaction. In a Diels–Alder reaction, carbon materials can be used as a diene or a dienophile. Here, carbon materials are used as dienes and alkyne-terminated derivatives as dienophiles. Different carbon materials, i.e., glassy carbon, carbon powder (carbon black), pyrolytic graphite carbon materials, and graphene, were functionalized by alkyne ferrocene derivatives or perfluoro-tagged alkyne molecules and characterized by electrochemical means, atomic force microscopy, and X-ray photoelectron spectroscopy experiments. This method allows for the rapid functionalization of carbon materials in mild conditions with high surface coverage.

International audience; Low electronic band gap 2D multilayered (n=3,4) lead-iodide perovskites with formula A’2An‑1PbnI3n+1 and A’’An‑1PbnI3n+1 are of great interest for photovoltaics, with recent demonstrations of stable solar cell operation based on 2D/3D bilayered heterostructures. Still, the difficulty in achieving optimal phase control, with potential formation of mixed n-domains, is a limiting factor for photovoltaic performance of 2D/3D heterostructures, and the current choice for multi n- layered compounds is limited. Here we report synthesis and XRD characterization of novel (I‑EA)2MAn-1PbnI3n+1 (n=1-4) compound series, along with (Br‑EA)2PbBr4 (n=1) compound, incorporating iodo-ethylammonium (I-EA) and bromo-ethylammonium (Br-EA) spacers. These halide-featuring spacers lead to small lattice mismatch between the inorganic and organic components, that explains the successful formation of multi n- layered compounds. The presence of bromine or iodine in the interlayer space impacts on the dielectric and electronic properties of these materials. Periodic DFT simulations predict vertical hole effective mass for n=1 (I‑EA)2PbI4 as small as 1.8 me, comparable to popular organic semiconductors, like rubrene. UV-vis characterization sets the optical absorption onset of these materials around 1.71 eV for n=3 and 4, hence suggesting these compounds can be successfully implemented in 2D/3D photovoltaic architectures.

International audience; The reactivity of benzo[1,2-b : 4,5-']dithiophene-4,8-dione in Pd-catalyzed C-H arylation was investigated. Using aryl bromides as aryl source in the presence of carbonate bases in 1,4-dioxane, the mono-C2-arylated benzo[1,2-b : 4,5-b']dithiophene-4,8-diones were regioselectively obtained. This procedure allowed to introduce both electron-rich and electron-poor aryl substituents on the benzo[1,2-b : 4,5-b']dithiophene-4,8-dione unit. These conditions were also effective for the coupling with 1-bromonaphthalene, 9-bromophenanthrene as well as aryl bromides bearing synthetically useful nitrile, chloro and methoxy substituents. The photophysical properties of representative arylated compounds have been performed by joint experimental and theoretical studies.

International audience; With amazing optical and electrochemical properties, the benzothioxanthene imide, a sulfur containing rylene, has only recently been demonstrated as a promising building block for organic electronics. As a result, the seminal synthetic procedure, published almost 50 years ago, has never been amended nor revisited so far. Given the great potential of this dye and numerous application perspectives, we thus report herein a significant update and modernization of its synthesis.

International audience; Synthesis and use of the unprecedented thiochromenocarbazole imide (TCI) for the preparation of printed, large-area and flexible OLEDs.

International audience; The chiral electroactive precursors diethyl-ethylenedithio-tetrathiafulvalene (DE-EDT-TTF 1) and tetraethyl-bis(ethylenedithio)-tetrathiafulvalene (TE-BEDT-TTF 2) have been synthesized in the racemic form and separated in pure enantiomers, together with the meso form of 2, by chiral HPLC. All the neutral forms (rac)-, (S)- and (R)-1, (rac)-, (S)-, (R)- and (meso)-2 have been structurally characterized by single crystal X-ray diffraction analysis. In all the structures the ethyl substituents are in axial positions, in agreement with the results of the DFT calculations, which indicate that the axial conformation of the ethyl substituents of 1 is more stable by 0.95 kcal mol−1 than the equatorial conformation in the gas phase. Circular dichroism measurements combined with TD-DFT calculations are also in favour of the predominance of the axial conformers in solution. The crystalline radical cation salt [(S)-1]PF6 and charge transfer complexes [(R)-1]TCNQF4 and [(meso)-2]TCNQF4 have been structurally characterized. A segregated donor–acceptor structure is observed for [(R)-1]TCNQF4, while in [(meso)-2]TCNQF4 donors and acceptors alternate in the stacks.

International audience; Aluminum Phthalocyanine Chloride (AlPcCl) is generally known as donor material in organic photovoltaic cells (OPVs). Nevertheless, in the present study we have demonstrated a successful use of AlPcCl as acceptor material to replace fullerene (C-60) in a planar heterojunction OPVs based Alpha-Sexithiophene (alpha-6T) as donor material. For this purpose, we have elaborated two series of OPVs: alpha-6T/AlPcCl and alpha-6T/C-60 using thermal sublimation technique. After the optimization of the AlPcCl thickness we have compared both solar cells current density vs. voltage characteristics, we have shown that the use of AlPcCl as acceptor instead of C-60 induces to an increase in the open circuit voltage (V-oc) and the short current density (J(sc)) values by 18% and 23%, respectively, from 0.5 to 0.61 V and from 6.10 to 7.98 mA/cm(2), while, we have obtained a decrease in the shunt resistance which has dropped the fill factor (FF) from 58 to 51%. The V-oc and J(sc) increase allows to increase the power conversion efficiency by 28%. These findings have been supported by absorbance measurements and morphological studies. The V-oc and J(sc) increase have been discussed and assigned to the difference between the theoretical V-oc of both heterojunctions, and to the complimentary absorption of AlPcCl with alpha-6T. While, the FF deceases has been attributed to the low electron mobility of AlPcCl compared with C-60. These findings, brought in the spotlight the potential of the metal phthalocyanines, which can open up a wide range of possibilities to test other materials based like this family.

International audience; Due to their numerous potential applications, the interest for the elaboration of new molecular switch has never stop to grow. Among them, multi-modal systems, where the switching between two different metastable states can be induced by using indifferently several kinds of stimulation, have a special place. In this study, we present our efforts to develop a class of multi-modal systems based on the association of a triphenylamine core with vinylpyrimidine units that exhibits nice acido and electrochromic properties. The most performant ones can present up to three different forms allowing to modulate their absorption and luminescence properties over three discrete levels. In order to provide limitations and outlooks for such systems, their switching behaviors have been rationalized by the help of DFT and TD-DFT calculations.

Flattening helices while keeping the handedness: On-surface cyclodehydrogenation of bishelicene enantiomers leads stereospecifically to (M,M) and (P,P) chiral planar polyaromatic hydrocarbons. This is followed by their homochiral aggregation into a 2D conglomerate. Thermally induced cyclodehydrogenation proceeds stereospecifically to chiral, planar coronocoronene. Such a reaction is a special example of topochemistry in which enantiospecific conversion is supported by the alignment of the reactant by the surface.

International audience; Dithia-[7]helicene and quasi[8]circulene have been formed on the 1,3-dithiol-2-one ring by oxidative dehydrocyclisation of bis-naphthothiophenyl-1,3-dithiol-2-one. Quasi-circulenes are easily obtained at room temperature by successive dehydrocyclisations regardless the amount of oxidation reagent whereas selectivity towards helicene, involving a single dehydrocyclisation, has been achieved only at low temperature. DFT calculations suggest a mechanism via a dication intermediate rather than a mono-cation for the formation of the quasi-circulenes whereas the helicene should be formed via a radical cation intermediate. While dithia[7]helicene is known to give stable stereoisomers, here the unsubstituted dithia-quasi[8]circulene shows unprecedented configurational stability of the enantiomers, with a theoretically estimated enantiomerisation energy barrier of 30.4 kcal mol−1, in excellent agreement with the experimentally determined value of 29.8 kcal mol−1. The enantiomers of both helicene and quasi-circulene have been separated by chiral chromatography and their absolute configuration assigned from the calculated CD spectra.

International audience; The use of Non-Fullerene Acceptors (NFAs) in the active layer of organic solar cells (OSCs) has made it possible to exceed 18% conversion efficiency. However, OSCs still present stability issues under operational conditions that need to be surpassed for their industrialization. In this work, we investigated binary and ternary blends to examine their efficiency and their stability as active layers of OSCs. We used a fluorinated polymer (PF2) as an electron donor and two different electron acceptors, a fullerene derivative (PC 71 BM) and a NFA (EH-IDTBR). We demonstrated that using EH-IDTBR instead of PC 71 BM leads to a decrease in efficiency attributed to the low out-of-plane electron mobility measured in the blend. However, using EH-IDTBR as single electron-acceptor significantly enhanced the OSCs stability under continuous illumination. Ternary blends were tested to reach simultaneously a high efficiency and a long-term stability. The best efficiency/stability compromise appeared to be when using EH-IDTBR only as electron-acceptor. We identified changes in the main charge-carrier recombination mechanism in photo-degraded devices from bimolecular in low EH-IDTBR content blends to trap-assisted in high EH-IDTBR ones. Finally, the blend morphology at a nanometer scale appeared as stable in high EH-IDTBR content blends while photo-degradation impacted significantly the morphology of the low EH-IDTBR content blend.

For DFT calculations, this work was granted access to the HPC resources of TGCC/CINES/IDRIS under the allocation 2020-A0090907682 made by GENCI; International audience; Metal-halide perovskites have recently demonstrated great potential for a wide variety of optoelectronic applications, with their layered subfamily offering improved stability as compared to their 3D analogs. Among the layered compounds, subclass of terminated compounds are currently dominating the field, while subclass is comparably much less explored. Here we report on the synthesis of (FA) 3 (HEA) 2 Pb 3 I 11 obtained by room-temperature liquid-gas diffusion involving the intermediate-size cation hydroxyethylammonium (HEA +), formamidinium (FA +) and PbI 2 dissolved in an acidic solution. This multilayered hybrid perovskite is a rare example of a m= 3 member of the -oriented series (A') 2 (A) m B m X 3m+2. Structural characterization based on X-ray diffraction and NMR investigations reveals that the small size cation FA + is located both in the inner layer of the perovskite sheet, but also in the interlayer space, while the intermediate-size cation HEA + is situated in the outer cavities of the perovskite sheet. (FA) 3 (HEA) 2 Pb 3 I 11 exhibits a broad absorption band in the visible region (400-650 nm) leading to an optical band gap of 1.96 eV. Electronic structure calculations confirm the direct nature of the band gap and evidence sizeable inter layer electronic coupling related to short I…I distances. These features are reminiscent of those observed for -oriented Pb 3 I 10 analogs that have shown photovoltaic efficiencies over 18%. These findings should prompt further investigations for the design of other -oriented multilayered (m= 3, 4,…) metal halide perovskites.

International audience; The electrical and optical properties of MoO3/Ag/MoO3 multilayer structures have been studied using the Ag deposition rate and layer thicknesses as parameters. When the silver film is deposited at 0.20 nm/s rate, the silver layer thickness necessary to achieve the percolation threshold of the resistivity ρ towards conductive structures is 10 nm. Below 10 nm, the films are semiconductor and above the films are conductors. In the present work, the variation of the thicknesses of top and bottom MoO3 layers is shown to strongly modify the optical properties of the multilayer structures. By using a Ag thickness of 10 nm, we demonstrate an increasing of the transmittance of the MoO3/Ag/MoO3 structures by optimizing the MoO3 layers thicknesses. When the MoO3 bottom layer is 20 nm thick, and the MoO3 top layer is 35 nm, the maximum transmission is 86% at the wavelength of 465 nm, while the averaged transmission in the visible range (350 nm-800 nm) is 70%. The best measured conductivity, σ = 1.1 × 105 (Ω cm)−1, corresponds also to this MoO3 (20 nm)/Ag (10 nm)/MoO3 (35 nm) structure. A good qualitative agreement between the theoretical calculations of the variation of the optical transmittance and reflectance of the MoO3/Ag/MoO3 structures is also highlighted.

International audience; Four D-π-A push–pull derivatives either based on a diphenylmethylamine or a 9-methylcarbazole electron-rich block (D), connected to a dicyanovinyl accepting moiety (A) through two different spacers (π), namely a thiophene or selenophene, were synthesized and characterized. These small and synthetically accessible molecules were indeed selected to rationalize the impact of both i) the rigidification of the arylamine part and ii) the nature of the π-spacer constituting heteroatom on the optical, electrochemical, charge transport and therefore photovoltaic properties

International audience; Dedicated to Jean-Pierre Dutasta and Christian Roussel on the occasion of their retirement and to all scientists who contributed to the development of Chirality in France. Historically, the tremendous role played by French scientists in the importance of chirality in chemistry, physics, biology, medicine, or materials science, starting with the pioneering works and discoveries of Augustin Fresnel, Jean-Baptiste Biot, Louis Pasteur, or Aimé Cotton, has been largely acknowledged by the international scientific community. The French chemists and physicists interested by chirality in the broadest sense continued this tradition over the years by being very actively involved in many chirality related research fields such as enantioselective synthesis and catalysis, analytical and chiral separation techniques, chiroptical spectroscopies, theoretical approaches, supramolecular chemistry, polymers, biomimetic systems, chiral materials, and fundamental physics. Witnessing the ever growing interest in France of this interdisciplinary topic, a French network in chirality supported by the CNRS (GDR Chirafun),gathering about 30 chemistry and physics teams from different Institutes, has emerged in 2015, following the organization of the "André Collet Chirality Days" in 2009 and2012, which were then continued in 2015 and 2018 under the auspices of the Chirafun network, with a new edition planned for October 2022.In this year 2022 marking the bicentenary of Louis Pasteur's birth, we are deeply pleased and honored to introduce this special virtual issue of Chirality gathering 19 very high quality articles spanning different chirality related fields covering

International audience; Enantiopure helicene-based bis(pyrazol-1-yl)pyridine (bpp-[6]helicene), with the helicene unit in position 4 of the pyridine ring, have been prepared and structurally characterized. Their chiroptical properties have been studied experimentally, and both absorption and circular dichroism (CD) spectra have been reproduced theoretically by time-dependent density functional theory (TDDFT). Remarkably, in spite of the remote localization of the helicene with respect to the coordination pocket of the bpp motif, chiral Eu(III) complexes based on these ligands show, however, circularly polarized luminescence in the visible region, sustained by TDDFT and CASSCF calculations, which also emphasize the possible antenna effect of the bpp ligand.

Three 2,1,3-benzothiadiazole-based ligands decorated with two pyridyl groups, 4,7-di(2-pyridyl)-2,1,3-benzothiadiazol (2-PyBTD), 4,7-di(3-pyridyl)-2,1,3-benzothiadiazol (3-PyBTD) and 4,7-di(4-pyridyl)-2,1,3 benzothiadiazol (4-PyBTD), generate ZnII and AgI complexes with a rich structural variety: [Zn(hfac)2(2-PyBTD)] 1, [Zn2(hfac)4(2-PyBTD)] 2, [Ag(CF3SO3)(2-PyBTD)]23, [Ag(2-PyBTD)]2(SbF6)24, [Ag2(NO3)2(2-PyBTD)(CH3CN)] 5, [Zn(hfac)2(3-PyBTD)] 6, [Zn(hfac)2(4-PyBTD)] 7, [ZnCl2(4-PyBTD)2] 8 and [ZnCl2(4-PyBTD)] 9 (hfac = hexafluoroacetylacetonato). The nature of the resulting complexes (discrete species or coordination polymers) is influenced by the relative position of the pyridyl nitrogen atoms, the nature of the starting metal precursors, as well as by the synthetic conditions. Compounds 1 and 8 are mononuclear and 2, 3 and 4 are binuclear species. Compounds 6, 7 and 9 are 1D coordination polymers, while compound 5 is a 2D coordination polymer, the metal ions being bridged by 2-PyBTD and nitrato ligands. The solid-state architectures are sustained by intermolecular π–π stacking interactions established between the pyridyl group and the benzene ring from the benzothiadiazol moiety. Compounds 1, 2, 7–9 show luminescence in the visible range. Density Functional Theory (DFT) and Time Dependent Density Functional Theory (TD-DFT) calculations have been performed on the ZnII complexes 1 and 2 in order to disclose the nature of the electronic transitions and to have an insight on the modulation of the photophysical properties upon complexation.

oral; National audience

Computational investigations were conducted thanks to HPC resources provided by [TGCC/CINES/IDRIS] under the allocation 2020-A0010907682 made by GENCI.; International audience; Halide perovskites and related nanostructures show complex structural interplay between well-defined long-range structural order, associated to their corner-shared MX6 organization, and short-range dynamic disorder, due to the soft nature of the lattice, libration motion and conformational freedom of the organic component. The structural characterization of these materials reveals therefore challenging, as it calls for an appropriate description of both short-range and long-range structural features, then requiring a smart combination of different structural investigation techniques. In this frame, solid state Nuclear Magnetic Resonance (ss-NMR) emerges as unique technique to complement long-range description routinely addressed via X-ray diffraction, to probe the material structure at different scales[1].We perform ss-NMR characterization of halide perovskites adopting synergic experimental and theoretical tools. The ss-NMR of 3D methylammonium lead halide perovskites is investigated, first, via periodic Density Functional Theory (DFT) simulations, with good match between the theoretical results for 1H and 13C nuclei and the experimental literature data. Theoretical/experimental agreement is comparably less accurate for 207Pb nuclei, due to lack of Spin-Orbit-Coupling (SOC) in our computational set-up, but still provides correct trends with respect to the PbX6 octahedra halide composition, hence making the NMR signature of 207Pb the ideal marker for characterizing halide segregation down to the atomic scale.[2] Further investigations involve a recently synthesized terminated, m=3 halide perovskite. Again, ssNMR of 207Pb nicely distinguishes between the lead atoms in the inner and outer layers.[3] Further efforts in the directions of incorporation of SOC in the computational set-up and better framing of thermal narrowing is needed but the present results highlight the potential of joint theoretical/experimental NMR simulations in the field of halide perovskites for energy conversion applications.[1] Dahlman C. J., Kubicki D. J., Reddy G. N. M., Interfaces in metal halide perovskites probed by solid-state NMR spectroscopy, J. Mater. Chem. A, 2021,9, 19206[2] Quarti C., Furet E., Katan C., DFT simulations as valuable tool to support NMR characterization of halide perovskites: the case of pure and mixed halide perovskites, Helv. Chim. Acta 2021, 104, e2000231.[3] M. Ben Haj Salah, N. Mercier, M. Allain, A. Leblanc, J. Dittmer, C. Botta, C. Quarti, C. Katan, Synthesis and characterization of (FA)3(HEA)2Pb3I11: a rare example of -oriented multilayered halide perovskite, accepted in Chemistry of Materials.

International audience; Light-emitting polymer nanotubes with tailored fluorescence emission bands have been prepared using organic emissive materials based on benzofuran, carbazole, and indolocarbazole scaffolds and investigated with the goal to obtain pure white-light emission at the nanoscale. The polymer nanostructures were obtained by the anodic aluminium oxide (AAO) template method with PMMA as a transparent polymer matrix and a proficient choice of organic dyes emitting in the blue, green, yellow and red parts of the spectral range. It is demonstrated that combining aqueous dispersions of monochromatic nano-tubes is an effective way of generating white light emission due to a simple correlation between the individual color components. Furthermore, it is also possible to target white emission at the nanoscale by adjusting the concentration of the dyes inside single nanotubes in order to obtain optimal color coordinates of ca. 0.3 in the CIE chromaticity diagram.

International audience; A M2L2 metalla-macrocycles contructed through coordination driven self-assembly from the Pd(dppf)OTf2 complex (dppf = 1,1′-Bis(diphenylphosphino)ferrocene) and an electron-rich 9-(1,3-dithiol-2-ylidene)fluorene bis-pyridyl ligand is depicted. This molecular tweezer exhibits a cavity able i) to promote dimerization upon oxidation and ii) to bind an electro-deficient substrate with a remarquable association constant. Those properties are compared with those of a previously described regioisomer.

Two push–pull derivatives based on a N,N-bis(4-biphenylyl)aniline (BPA) donor block connected to a dicyanovinyl accepting moiety by thienyl and bithienyl π-conjugated spacers have been synthesized and characterized. All-small-molecule planar-heterojunction organic solar cells show promising power conversion efficiencies and impressive fill factor (>73%) correlated with the high hole-mobility induced by the BPA moiety.

The UV-Vis spectroscopy and nonlinear-optical properties of new trans-dichloropalladium(II) complex of 7-azaindole have been investigated using computational chemistry and experimental method. Opti...

Electrocrystallization of the bis(ethylenedithio)tetrathiafulvalene (BEDT-TTF) organic donor in the presence of the [Fe(ClCNAn)3]3– tris(chlorocyananilato)ferrate(III) paramagnetic anion in different stoichiometric ratios and solvent mixtures afforded two different hybrid systems formulated as [BEDT-TTF]4[Fe(ClCNAn)3]·3H2O (1) and [BEDT-TTF]5[Fe(ClCNAn)3]2·2CH3CN (2) (An = anilato). Compounds 1 and 2 present unusual structures without the typical segregated organic and inorganic layers, where layers of 1 are formed by Λ and Δ enantiomers of the anionic paramagnetic complex together with mixed-valence BEDT-TTF tetramers, while layers of 2 are formed by Λ and Δ enantiomers of the paramagnetic complex together with dicationic BEDT-TTF dimers and monomers. Compounds 1 and 2 show semiconducting behaviors with room-temperature conductivities of ca. 6 × 10–3 S cm–1 (ambient pressure) and 1 × 10–3 S cm–1 (under applied pressure of 12.1 GPa), respectively, due to strong dimerization between the donors. Magnetic measurements performed on compound 1 indicate weak antiferromagnetic coupling between high-spin FeIII (SFe = 5/2) and mixed-valence radical cation diyads (BEDT-TTF)2+ (Srad = 1/2) mediated by the anilate ligands, together with an important Pauli paramagnetism typical for conducting systems., This work was supported in France by the CNRS, the University of Angers, the RFI Regional LUMOMAT project ASCO-MMM (grant to A.A.). The work in Italy was supported by the Fondazione di Sardegna-Convenzione triennale tra la Fondazione di Sardegna e gli Atenei Sardi, Regione Sardegna-L.R. 7/2007 annualità 2016-DGR 28/21 del 17.05.2015 “Innovative Molecular Functional Materials for Environmental and Biomedical Applicatons” (grant to S.A.S.) and INSTM. M.J.O. acknowledges support from the Ministerio Español de Ciencia e Innovación (Project CTQ2016-75068P) and Unidad de Excelencia María de Maeztu (Project MDM-2015-0538). Work at Bellaterra (Spain) was supported by the Spanish MICIU through Grant PGC2018-096955-B-C44 and the MINECO through the Severo Ochoa Centers of Excellence Program under Grant SEV-2015-0496 as well as by Generalitat de Catalunya (2017SGR1506).

International audience; The exciton blocking layer (EBL) as an interfacial layer is extremely critical in determining the organic photo-voltaic cell (OPV) performances. Here, we studied inverted planar heterojunction solar cells PHJ-OPVs with the following configuration ITO/EBL/C60/CuPc/MoO3/Al. Upon the EBL functionality which can act as an exciton blocking layer and allows the electron collection at the cathode, we proposed the insertion of hybrid EBL con -sisted of KI/Alq(3) thin layer. The Alq(3) is known as an EBL due to its broad bandgap, whereas we found that when a thin layer of 1 nm of KI is introduced in ITO/Alq(3) interface, the KI decomposed during the thermal deposition, and only potassium interacts and diffuses in the Alq(3) layer, which effectively enhances the electrons collection at the ITO/C-60 interfaces leading to the improvement of open-circuit voltage (Voc), and device power conversion efficiency by 36% than the device using Alq(3) alone as EBL.

International audience; The synthesis, structural, photophysical characterization and theoretical studies on homo/heteroleptic neutral 2D layered coordination polymers (CPs), obtained by combining the erbium(III) ion with chlorocyananilates (ClCNAn) and/or tetrafluoroterephthalates (F4BDC) linkers, are herein reported. The structure of the heteroleptic Er III-based CP, formulated as [Er2(ClCNAn)2(F4BDC)(DMSO)6]n (1) is also reported. 1 crystallizes in the triclinic P-1 space group and the structure consists of neutral 2D layers formed by Er III ions linked through the two linkers oriented in such a way that the neighboring 2D layers are eclipsed along the a axis, leading to parallelogram-like cavities. Photophysical measurements highlight the prominent role of chlorocyananilate linkers as optical antennas toward lanthanide ions, while wave-function theory analysis supports the experimental findings providing evidence for the effect of ligand substitution on the luminescence properties of homo/heteroleptic 2D CPs.

International audience; Fine control of electrografting kinetics of diazonium salts is of paramount importance, particularly when considering the application of diazoniums for the fabrication of 2D nanomaterials. In this work, we develop controlled grafting of a perylenediimide (PDI) moiety separated with a 12-carbon aliphatic chain from aryldiazonium. The particular design of the diazonium cation synthesized for this study allows for fine tuning of the surface coverage by simple adjustment of the applied potential. Indeed, according to the potential imposed at the working electrode, the PDI moiety can either enhance the charge propagation within the growing layer or consume the diazonium salt in the bulk solution via redox cross-reaction. With this approach, the surface functionalization can be restricted to a monolayer or a multilayer in a robust and elegant manner, obeying Langmuir or first-order kinetics of electrografting, respectively. The experimental observations are supported with in situ spectroelectrochemical investigations aimed to differentiate the reduction of PDI moieties in the deposited layer and the bulk solution. A tentative mechanistic scheme is proposed, and numerical simulations are undertaken to rationalize the data.

The association of the electron acceptor 4,4’-amino-bipyridinium (AmV2+) dication and BiI3 in an acidic solution affords three organic−inorganic hybrid materials, (AmV)3(BiI6)2 (1), (AmV)2(Bi4I16) (2), and (AmV)BiI5 (3), whose structures are based on isolated BiI63− and Bi4I164− anion clusters in 1 and 2, respectively, and on a one-dimensional (1D) chain of trans-connected corner-sharing octahedra in 3. In contrast with known methylviologen-based hybrids, these compounds are more soluble in polar solvents, allowing thin film formation by spin-coating. (AmV)BiI5 exhibits a broad absorption band in the visible region leading to an optical bandgap of 1.54 eV and shows a PV effect as demonstrated by a significant open-circuit voltage close to 500 mV. The electronic structure of the three compounds has been investigated using first-principles calculations based on density functional theory (DFT). Unexpectedly, despite the trans-connected corner-shared octahedra, for (AmV)BiI5, the valence state shows no coupling along the wire direction, leading to a high effective mass for holes, while in contrast, the strong coupling between Bi 6px orbitals in the same direction at the conduction band minimum suggests excellent electron transport properties. This contributes to the low current output leading to the low efficiency of perovskite solar cells based on (AmV)BiI5. Further insight is provided for trans- and cis-MI5 1D model structures (M = Bi or Pb) based on DFT investigations.

International audience; One of the most straightforward strategies nowadays for the synthesis of carbo-and heterohelicenes is the oxidative photocyclisation of stilbene derivatives in the Mallory conditions. In this study, the reactivity of a series of 3,4-dihalostyryl-naphthalenes (Hal = Br, F and Cl) has been investigated in the Mallory conditions towards the corresponding halogenated [4]helicene compounds. The difluoro precursor afforded the two isomeric 2,3-and 1,2-difluoro-[4]helicenes, resulting from the ring closure on the two possible positions of the substituted benzene ring, the dichloro compound led to the formation of a mixture of the two isomeric 2,3 and 1,2-dichloro-[4]helicenes together with the 2-mono-chloro derivative, while the dibromo precursor provided, unexpectedly, only 2,3-dibromo-[4]helicene and the 2-mono-bromo derivative. DFT calculations performed on the entire series of precursors, final helicenes and intermediate dihydrohelicenes, including the non-halogenated congeners, reveal the highly energetically favorable formation of a second dihydrohelicene intermediate following a [1,9]hydrogen sigmatropic transposition. Whereas the existence of this transposed dihydrohelicene intermediate, more stable than the initially formed dihydrohelicene by fifteen to thirty kcal/mol, was hitherto "hidden" in the non-substituted series, it allows here to explain its re-aromatization through formal elimination of HX in order to provide the 2-mono-halogenated-[4]helicene derivatives.

While solar-to-fuel catalysis requires the careful transfer of electrons, there are still challenges understanding how electron spin contributes to reactivity. Here, authors employ chiral fused thiadiazole-helicenes to control spin polarization in oxygen evolution electrocatalysts., A sustainable future requires highly efficient energy conversion and storage processes, where electrocatalysis plays a crucial role. The activity of an electrocatalyst is governed by the binding energy towards the reaction intermediates, while the scaling relationships prevent the improvement of a catalytic system over its volcano-plot limits. To overcome these limitations, unconventional methods that are not fully determined by the surface binding energy can be helpful. Here, we use organic chiral molecules, i.e., hetero-helicenes such as thiadiazole-[7]helicene and bis(thiadiazole)-[8]helicene, to boost the oxygen evolution reaction (OER) by up to ca. 130 % (at the potential of 1.65 V vs. RHE) at state-of-the-art 2D Ni- and NiFe-based catalysts via a spin-polarization mechanism. Our results show that chiral molecule-functionalization is able to increase the OER activity of catalysts beyond the volcano limits. A guideline for optimizing the catalytic activity via chiral molecular functionalization of hybrid 2D electrodes is given.

International audience

Racemic and enantiopure nickel(II) bis(dithiolene) anionic and neutral complexes based on the methyl-5,6-dihydro-1,4-dithiin-2,3-dithiolate (me-dddt) and dimethyl-5,6-dihydro-1,4-dithiin-2,3-dithiolate (dm-dddt) ligands have been experimentally and theoretically investigated with a special focus on their chiroptical properties. According to the time-dependent density-functional theory (TD-DFT) calculations, the strong near-infrared absorption bands typical for such complexes are only weakly active in circular dichroism (CD), and moreover, they have opposite signs for the axial and equatorial conformations, due to the variation of the angle between the transition electric and magnetic dipole moments, thus leading to the mutual cancellation of their contributions and the absence of these bands in the experimental CD spectra. The influence of the number of stereogenic centers and of the oxidation state of the complexes on their chiroptical properties is highlighted. The solid-state structure of the complex (TMA)[Ni(rac-me-dddt)2 ] (TMA = tetramethylammonium), determined by single-crystal X-ray diffraction analysis, shows a rather unusual cis arrangement of the two dithiolene ligands, with the methyl substituents adopting an axial conformation, which is not the most stable one in the gas phase.

Electrocrystallization of tetramethyl-bis(ethylenedithio)-tetrathiafulvalene (TM-BEDT-TTF) (1) as pure (S,S,S,S) and (R,R,R,R) enantiomers in the presence of (n-Bu4N)2(Mo6O19) and chloroform or bromoform afforded a series of four isostructural enantiopure radical cation salts [(S/R)-1]9(Mo6O19)5·(CHX3)2 (X = Cl, Br) crystallizing in the trigonal non-centrosymmetric space group R32. In the formula unit there are six donors of type A and three donors of type B showing, respectively, (ax, ax, eq, eq) and all-ax conformations (ax = axial, eq = equatorial) of the methyl substituents. The donors form a hexagonal network in the ab plane with a helical twist between them leading to lateral orbital overlap interactions. Electrocrystallization of the racemic donor provided the compound [(rac)-1]2(Mo6O19) which crystallized in the monoclinic system P21/n. Single crystal resistivity measurements show semiconducting behaviour of the enantiopure materials with a relatively high room temperature conductivity of 0.8–1.2 S cm−1, but rather insensitive to applied pressures of up to 2.3 GPa. Analysis of the electronic structure of the conducting solids through extended Hückel tight-binding band structure calculations indicates a Mott insulator behaviour explaining the semiconducting character and suggests that these compounds are valuable candidates for Dirac cone materials. Further insight into the conducting properties is provided by preliminary field effect transistor measurements., This work was supported in France by the National Agency for Research (ANR, Project 15-CE29-0006-01 ChiraMolCo), the CNRS and the University of Angers. Work at Bellaterra (Spain) was supported by the Spanish MICIU through Grant PGC2018-096955-B-C44 and the Severo Ochoa FUNFUTURE (CEX2019-000917-S) Excellence Centre distinction as well as by Generalitat de Catalunya (2017SGR1506). This work was also partially supported in Chiba, Japan by MEXT = JSPJ KAKENHI under Grants No. 16H06346 and 20K03870. Work in Okazaki was supported by Grant-in-Aid for Scientific Research (A) (Grant Number 19H00891) and Grant-in-Aid for Challenging Research (Exploratory) (Grant Number 20K20903) from JSPS as well as PRESTO (Grant Number JPMJPR20L9) from JST.

Singlet-triplet interconversions (intersystem crossing, ISC) in organic molecules are at the basis of many important processes in cutting-edge photonic applications (organic light-emitting devices, photodynamic therapy, etc.). Selection rules for these transitions are mainly governed by the spin-orbit coupling (SOC) phenomenon. Although the SOC relies on complex relativistic phenomena, theoreticians have, with time, developed increasingly sophisticated and efficient approaches to gain access to a satisfactory evaluation of its magnitude. However, recent works have highlighted the remarkable and somehow unexpected efficiency of dimers of small conjugated molecules in terms of ISC quantum yields, whose origin has not been completely investigated. In this work, we bring a coupled experimental and theoretical analysis of the origin of the unusually large ISC efficiency on a series of such dimers that differ by their nature (covalent or supramolecular). We show that considering the dynamical nature of the SOC, and especially its dependence on angular orientations between the dimer subunits sometimes overlooked in the literature, it is necessary to rationalize some counterintuitive experimental observations. This combined experimental and theoretical work paves the way for new molecular engineering rules for SOC control.

International audience; The controlled preparation of chiral emissive transition metal complexes is fundamental in the field of circularly polarized luminescence (CPL) active molecular materials. For this purpose, enantiopure Zn(II) complexes 1 and 2 based on a tetradentate salen ligand surrounded by [4]helicene moieties, together with their racemic counterpart 3, have been herein synthesized. Chirality is primarily brought about by chiral 1,2-cyclohexane-diamines. Alternatively, achiral complex 4 based on ortho-phenylene-diamine has been prepared as well. Single crystal X-ray diffraction analyses have been performed on helicenic intermediates 8 and 9 and complexes 1 and 4. Complexes 1 and 4 display the typical tetradentate O,N,N,O coordination around Zn(II) characteristic of salen ligands, and bear two [4]helicene moieties. The zinc complexes are luminescent in the visible range around 560 nm at room temperature in aerated solutions with the QY reaching ca. 15% for a luminescence lifetime of 5.5 ns. The optical activities of these complexes have been assessed by CD and CPL, and compared to DFT calculations.

We report the use of poly(3,4-ethylenedioxythiophene):polystyrene sulfonate (PEDOT:PSS) as a transducing material in the fabrication of mechanical-to-electrical conversion devices based on the flexoelectric-like response of this polymer. Devices are made in a cantilever-based three-layer stainless-steel/PEDOT:PSS/top metal electrode configuration to assess the effective transverse flexoelectric coefficient μ 12 ′. We investigated the influence of the nature of the top electrode in the flexoelectric response comparing samples with gold and aluminum top electrodes and demonstrated the huge impact of adding a small fraction of a second dopant such as xylitol to the PEDOT:PSS polymer blend and the benefits of a post-treatment of the polymer film with ethanol and methanol on the flexoelectric coefficient. The combination of xylitol addition and the rinsing of the polymer films with ethanol and methanol, along with the use of gold as a top electrode, led to a significant improvement of μ 12 ′ to ca. 24 μC m−1, which is in the range of those reported for high permittivity oxide materials. These findings support the use of conjugated polymers as an alternative to inorganic materials in flexoelectric-based applications, where large flexibility is required.

International audience; Advancing non-fullerene acceptor (NFA) organic photovoltaics requires the mitigation of the efficiency-limiting processes. Acceptor end-group and side-chain engineering are two handles to tune properties, and a better understanding of their specific impact on the photophysics could facilitate a more guided acceptor design. Here, the device performance, energetic landscape, and photophysics of rhodanine and dicyanovinyl end-capped IDT-based NFAs, namely, O-IDTBR and O-IDTBCN, in PCE10-based solar cells are compared by transient optical and electro-optical spectroscopy techniques and density functional theory calculations. It is revealed how the acceptors’ quadrupole moments affect the interfacial energetic landscape, in turn causing differences in exciton quenching, charge dissociation efficiencies, and geminate versus non-geminate recombination losses. More precisely, it is found that the open circuit voltage (VOC) is controlled by the acceptors’ electron affinity (EA), while geminate and non-geminate recombination, and the field dependence of charge generation, rely on the acceptors’ quadrupole moments. The kinetic parameters and yields of all processes are determined, and it is demonstrated that they can reproduce the performance differences of the devices’ current–voltage characteristics in carrier drift-diffusion simulations. The results provide insight into the impact of the energetic landscape, specifically the role of the quadrupole moment of the acceptor, beyond trivial considerations of the donor–acceptor energy offsets.

According to the latest report from the World Health Orgamization (WHO), malaria remains a disease having a strong negative impact on the African population, especially Ivory Coast population. In view of the health, economic and financial burden caused by this disease, our study was to develop new techniques for malaria diagnosis in Ivory Coast. Our contributions in this thesis concern two major levels: the construction of an optical system and the development of image processing techniques, which combined together allowed the distinction of infected blood cells from uninfected ones.First, following a partnership between the Laboratory of Instrumentation, Image and Spectroscopy (L2IS) and the University of LUND in Sweden, we built a new model of multispectral and multimodal microscope. It is an improvement of the standard optical microscope found in health centers in Ivory Coast. It is also an improvement of the microscope (multispectral and multimodal) that we found arriving at L2IS. The system we built has the particularity of being extensible. It means it can be adapted to the needs of the user both in terms of imaging modalities and in terms of the illumination sources used. We modified and adapted it to malaria diagnosis purpose. For this purpose, we equipped the system with lasers whose wavelengths are 405 nm, 450 nm, 538 nm and 638 nm. The wavelengths chosen are those which are the most discriminating for malaria parasites detection. Our experiments were performed by acquiring multispectral images using the system we built and the one we found at L2IS upon our arrival (it consists of 13 light emitting diodes ranging from 375 nm to 940 nm). We finally obtain multi-component images consisting of the one hand of four (4) spectral planes and on the other hand of thirteen (13).Second, we developed image processing techniques to analyze images produced using the aforementioned multispectral and multimodal microscopes. The works of this part were performed following a partnership between L2IS and LARIS (Laboratoire Angevin de Recherche en Ingénierie des Systèmes) from University of Angers. These works were based on a multi-component texture analysis through Local Binary Pattern (LBP)technique. Resulting from statistical approaches, the choice of Local Binary Pattern (LBP) for the analysis of our images instead of frequency, morphological and structural approaches was adopted because of their simplicity and their robustness in textures classification. Its principle is based on locally describing a texture. Different variants have been developed to make them more robust: on the one hand, those improving the topology of the neighborhood, the sampling of the neighborhood, the thresholding, the quantization. On the other hand, the grouping and encoding of bits and finally the combination of LBP methods with each other or with other methods. We implemented several algorithms to conduct a comparative study between statisticalapproaches and other approaches on the one hand, and between different statistical approaches on the other 17hand. These algorithms were applied to the reference image databases that are Outex, Brodatz and Curet. From comparison tests, it emerges that the statistical approaches denote a higher rate of well-classified than those of other texture analysis approaches. Concerning the comparison tests from statistical approaches between them, the results show that the methods combining several variants of LBP provide better texture classification.Locals Binary Patterns were originally developed for grayscale images. Therefore, they are not straightforward applicable to multispectral images due to the presence of vectors instead of grayscale levels., Selon le dernier rapport de l’Organisation Mondiale de la Santé (OMS), le paludisme demeure une maladie présentant un fort impact négatif sur la population africaine notamment celle de la Côte d’Ivoire. Au regard du poids sanitaire, économique et financier provoqué par cette maladie, notre étude a été de développer de nouvelles techniques destinées au diagnostic du paludisme en Côte d’Ivoire. Nos contributions dans cette thèse se situent à deux niveaux majeurs que sont la construction d’un système optique et le développement de techniques de traitement d’images ; lesquels combinés a permis la distinction de cellules sanguines infectées de celles non infectées par le paludisme.Dans un premier temps nous avons, à la suite d’un partenariat entre le Laboratoire d’Instrumentation, Image et Spectroscopie (L2IS) et l’université de LUND en Suède, implémenté un nouveau modèle de microscope multispectral et multimodal. Il est une amélioration du microscope optique standard rencontré dans les centres de santé en Côte d’Ivoire. Il est également une amélioration du microscope (multispectral et multimodal) que nous avons trouvé à notre arrivée au L2IS. Le système construit présente la particularité d’être extensible c’est-à-dire pouvant être adapté aux besoins de l’utilisateur tant au niveau des modalités d’imagerie qu’au niveau des sources d’illumination utilisées. Nous l’avons modifié et adapté à notre objectif applicatif qui est le diagnostic du paludisme. A cet effet, nous l’avons équipé de lasers de longueurs d’ondes de 405 nm, 450 nm, 538 nm et 638 nm. Les longueurs d’ondes choisies sont celles étant les plus discriminantes pour le diagnostic du paludisme. Nos expérimentations ont été réalisées en acquérant des images multispectrales en utilisant le système que nous avons construit et également en utilisant le système trouvé au sein du L2IS à notre arrivée (constitué de 13 diodes électroluminescentes allant de 375 nm à 940 nm). Nous obtenons finalement des images multi-composantes constituées d’une part de quatre (4) plans spectraux et d’autre part de treize (13). Dans un deuxième temps, nous avons développé des techniques de traitement d’images pour l’analyse des images produites en utilisant les microscopes multispectraux et multimodaux précédemment cités. Les travaux relatifs au développement de ces techniques de traitement d’images ont été réalisés à la suite d’un partenariat entre le L2IS et le LARIS (Laboratoire Angevin de Recherche en Ingénierie des Systèmes) sis à l’Université d’Angers. Ces travaux reposent sur une analyse de textures multi-composantes basée sur les Local Binary Pattern (LBP). Issus des approches statistiques, le choix des Local Binay Pattern (LBP) pour l’analyse de nos images vis-à-vis des approches fréquentielles, morphologiques et structurelles a été adopté en raison de leur simplicité et de leur robustesse dans la classification de textures. Ils permettent de décrire localement la texture d’une image. Différentes variantes ont été développées afin de les rendre plus robustes : D’une part, celles améliorant la topologie du voisinage, l’échantillonnage du voisinage, le seuillage, la quantification. D’autre part, le regroupement et l’encodage des bits puis enfin la combinaison des méthodes LBP entre elles ou avec d’autres méthodes.

International audience; The N-alkylation of diketopyrrolopyrroles (DPPs) represents a fundamental step to ensure solubility and further processability. Commonly used nucleophilic substitution in halogenated derivatives is replaced in this work by the Mitsunobu reaction affording unprecedented DPPs with α-branched and chiral chains.

Methyl-ethylenedithio-tetrathiafulvalene (Me-EDT-TTF (1) and dimethyl-ethylenedithio-tetrathiafulvalene (DM-EDT-TTF (2) are valuable precursors for chiral molecular conductors, which are generally obtained by electrocrystallization in the presence of various counter-ions. The number of the stereogenic centers, their relative location on the molecule, the nature of the counter-ion and the electrocrystallization conditions play a paramount role in the crystal structures and conducting properties of the resulting materials. Here, we report the preparation and detailed structural characterization of the following series of radical cation salts: (i) mixed valence (1)2AsF6 as racemic, and (S) and (R) enantiomers; (ii) [(S)-1]AsF6·C4H8O and [(R)-1]AsF6·C4H8O where a strong dimerization of the donors is observed; (iii) (1)I3 and (2)I3 as racemic and enantiopure forms and (iv) [(meso)-2]PF6 and [(meso)-2]XO4 (X = Cl, Re), based on the new donor (meso)-2. In the latter, the two methyl substituents necessarily adopt axial and equatorial conformations, thus leading to a completely different packing of the donors when compared to the chiral form (S,S)/(R,R) of 2 in its radical cation salts. Single crystal resistivity measurements, complemented by thermoelectric power measurements in the case of (1)2AsF6, suggest quasi-metallic conductivity for the latter in the high temperature regime, with σRT ≈ 1–10 S cm–1, while semiconducting behavior is observed for the (meso)-2 based salts.

International audience; The surface modification by organics has been booming over the past twenty years in the context of thedevelopment of 2D nanomaterials for a wide range of applications. The diazonium salt chemistryrepresents a valued approach since it allows the covalent attachment, under mild experimentalconditions, of functional moieties to various substrates. The potential of this method can be greatlyenhanced by exploiting it to prepare reactive organic layers intended for the coupling of more complexmolecular structures. This two-step approach, called ‘‘post-functionalization’’, has been successfullyexploited to provide working surfaces for a wide variety of applications such as sensors, catalysis, energystorage or nanoelectronics. This review aims to detail all the chemical coupling methods implementedon modified substrates via the diazonium chemistry (352 references), with an emphasis on theexperimental conditions used and on the efficiency of the couplings. An overall table collects thereferences, classified by coupling method, modified substrate and targeted application.

International audience

International audience; Straightforward palladium(II) catalyzed direct cross-coupling reaction between decyl, (S)-2-methyl-butyl, and dodecyl N-substituted diketopyrrolopyrrole thiophene (DPPT), including a 3-methoxy-thiophene derivative, and 6-bromo-2,2’-bipyridine afforded a series of mono- and bis-bipyridine substituted DPPT ligands 1-3. Complexation reactions with PtCl(2)(DMSO)(2) provided ortho-metalated platinum(II) complexes 1-Pt and 2-Pt, together with the N^N^O complex 3d-Pt(N^N^O) resulted from the O-Me activation of the intermediary complex 3d-Pt(N^N). The ligand 1b and the mononuclear complexes 1a-Pt and 1b-Pt have been structurally characterized by single crystal X-ray structure, evidencing the establishment of numerous intermolecular π–π interactions in the solid state. Moreover, in the crystal structure of the model complex DMTB-Pt(N^N^O) (DMTB = 3,4-dimethoxy-(2,2′-bipyridine)) the chelating tridentate N^N^O mode is clearly evidenced. The chiral ligand 1b and its mononuclear complex 1b-Pt do not show any CD signal in solution, but they are CD active in the solid state with bisignate bands in the low energy region, opposite in sign between the ligand and the complex, suggesting helical supramolecular arrangement of the dpp chromophore in the solid state. Photophysical investigations demonstrate that all of the ligands are fluorescent with high quantum yields, while the emission is quenched for the complexes, except partially in 3d-Pt(N^N), very likely through an intersystem crossing mechanism promoted by the heavy metal. Density functional theory calculations support the differences observed between the absorption properties of the ligands, ortho- and non-ortho-metalated complexes. The highly fluorescent bipyridine ligands reported herein open the way toward multifunctional transition metal complexes and their use in organic electronics.

International audience; The pallado-catalyzed cyanation of benzothioxanthene imide (BTXI) derivatives is explored herein. Once optimized on the monobromo BTXI, mild reaction conditions were successfully applied to the dibromo derivative affording two regioisomers that have been isolated and structurally solved. Additional hydrogen-deuterium exchange experiments were carried out to support a proposed mechanism involving the formation of a five-membered palladacycle intermediate in the bay area. In addition to impact the structural, photo physical and electrochemical properties of the BTXI core, nitrile moieties were successfully used as orthogonal protecting groups thus opening doors to new design principles.

International audience; The first synthesis of an original octamer consisting of a central polyhedral oligomeric silsesquioxane (POSS) cage decorated with electro- and optically active arylamine-based push–pull building-blocks is reported herein. Once fully characterized, the potential of the new compound was evaluated as donor material in bulk heterojunction organic solar cells. With promising power conversion efficiencies, good processability and film forming properties, such multimer architectures turns out to be potential candidates to bridge the gap between small molecules and polymers.

ACS Award in the Chemistry of Materials (2020): Symposium Honoring David Brian Mitzi; International audience; Layered halide perovskites are a class of semiconductors produced via chemical approaches andshowing unique opto-electronic properties. Pioneered by Prof. David Mitzi in the 1990s, these materials have anatural quantum-well electronic structure (the band-gap of the inorganic frame is embedded into that of theorganic spacers) and feature positive transport properties, effective visible-light absorption, narrow excitonicemission, etc.The full exploitation of these perovskites cannot go without deep understanding of their native electronic andoptical properties, as accessible, via complex experimental set-ups and computationally expensive ab-initiocalculations. However, interpretation of experimental and theoretical results can greatly benefit from basic“pencil-and-paper” symmetry analysis. Based on group-theory, we discuss how the change in thedimensionality influences the corresponding electronic and optical properties. In the direct band gap quantumwellscenario, we highlight how the breaking of the chemical connectivity influences the electronic structure, interms of hybridization of the composing atoms (see Figure a). We also discuss the corresponding evolution ofthe optical properties, with focus on the lowest energy exciton fine structure. The present analysis will be thenextended to the case of defective-halide perovskite frames, a class of systems recently reported in theliterature.As an alternative scenario, substitution of commonly used saturated organic spacers with molecules featuringextended π-conjugation breaks the quantum-well picture. Indeed, the band-gap closing due to extended π-system can result in the (de)stabilization of the frontier orbitals of the spacer, compared to those of theinorganic frame, leading to the formation of a type II heterojunction at the organic/inorganic interface (seeFigure b). We discuss the related charge/energy transfer processes on the basis of recently reportedPbX (X=Cl,Br) layered perovskite frame incorporating tetrazine derivative as spacer. Featuring resonancesboth for the single particle states and excitonic states, these systems allow to discuss several diversionchannels for the relaxation of carriers generated in the perovskite, in the detail.

Tetramethyl-tetraselenafulvalene (TMTSF) and bis(ethylenedithio)-tetrathiafulvalene (BEDT-TTF) are flagship precursors in the field of molecular (super)conductors. The electrocrystallization of these donors in the presence of (n-Bu4N)TaF6 or mixtures of (n-Bu4N)TaF6 and (n-Bu4N)PF6 provided Bechgaard salts formulated as (TMTSF)2(TaF6)0.84(PF6)0.16, (TMTSF)2(TaF6)0.56(PF6)0.44, (TMTSF)2(TaF6)0.44(PF6)0.56 and (TMTSF)2(TaF6)0.12(PF6)0.88, together with the monoclinic and orthorhombic phases δm-(BEDT-TTF)2(TaF6)0.94(PF6)0.06 and δo-(BEDT-TTF)2(TaF6)0.43(PF6)0.57, respectively. The use of BEDT-TTF and a mixture of (n-Bu4N)TaF6/TaF5 afforded the 1:1 phase (BEDT-TTF)2(TaF6)2·CH2Cl2. The precise Ta/P ratio in the alloys has been determined by an accurate single crystal X-ray data analysis and was corroborated with solution 19F NMR measurements. In the previously unknown crystalline phase (BEDT-TTF)2(TaF6)2·CH2Cl2 the donors organize in dimers interacting laterally yet no organic-inorganic segregation is observed. Single crystal resistivity measurements on the TMTSF based materials show typical behavior of the Bechgaard phases with room temperature conductivity σ ≈ 100 S/cm and localization below 12 K indicative of a spin density wave transition. The orthorhombic phase δo-(BEDT-TTF)2(TaF6)0.43(PF6)0.57 is semiconducting with the room temperature conductivity estimated to be σ ≈ 0.16–0.5 S/cm while the compound (BEDT-TTF)2(TaF6)2·CH2Cl2 is also a semiconductor, yet with a much lower room temperature conductivity value of 0.001 to 0.0025 S/cm, in agreement with the +1 oxidation state and strong dimerization of the donors.

Four new compounds of formulas [Cu(hfac)2(L)] (1), [Ni(hfac)2(L)] (2), [{Cu(hfac)2}2(µ-L)]·2CH3OH (3) and [{Ni(hfac)2}2(µ-L)]·2CH3CN (4) [Hhfac = hexafluoroacetylacetone and L = 3,6-bis(picolylamino)-1,2,4,5-tetrazine] have been prepared and their structures determined by X-ray diffraction on single crystals. Compounds 1 and 2 are isostructural mononuclear complexes where the metal ions [copper(II) (1) and nickel(II) (2)] are six-coordinated in distorted octahedral MN2O4 surroundings which are built by two bidentate hfac ligands plus another bidentate L molecule. This last ligand coordinates to the metal ions through the nitrogen atoms of the picolylamine fragment. Compounds 3 and 4 are centrosymmetric homodinuclear compounds where two bidentate hfac units are the bidentate capping ligands at each metal center and a bis-bidentate L molecule acts as a bridge. The values of the intramolecular metal···metal separation are 7.97 (3) and 7.82 Å (4). Static (dc) magnetic susceptibility measurements were carried out for polycrystalline samples 1–4 in the temperature range 1.9–300 K. Curie law behaviors were observed for 1 and 2, the downturn of χMT in the low temperature region for 2 being due to the zero-field splitting of the nickel(II) ion. Very weak [J = −0.247(2) cm−1] and relatively weak intramolecular antiferromagnetic interactions [J = −4.86(2) cm−1] occurred in 3 and 4, respectively (the spin Hamiltonian being defined as H = −JS1·S2). Simple symmetry considerations about the overlap between the magnetic orbitals across the extended bis-bidentate L bridge in 3 and 4 account for their magnetic properties.

New three-dimensional hole-transporting materials (HTMs) based on either 9,9′-spirobifluorene (SBF) or spiro-[cyclopenta[1,2-b:5,4-b′]dithiophene-4,9′-fluorene] (SDTF) core have been synthesized. A...

International audience; Contrary to aliphatic amines, aromatic amines have received less attention for the surface modification by oxidation due to the low acidity of their cation radicals. To overcome this limitation, bases are often added in solution to facilitate or make possible the grafting. However, there has only been a modest focus on their impact on the grafting efficiency. Here, the anodic behavior of a series of para-substituted anilines was investigated in the presence of different bases to address this issue. From complete sets of Brønsted acidity/basicity data and H-bond acidity/basicity factors for both parasubstituted anilines and bases, a grafting efficiency index was proposed as a practical tool to choose the most suitable base for the grafting. As a proof-of-concept for base-assisted grafting of aromatic amines, two aniline/base systems were tested to modify carbon surfaces at lower potential, compared to the modification achieved from pure aniline solutions.