253 research outputs found
Schiff-base [4]helicene Zn(ii) complexes as chiral emitters
No full textThe 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
Reinecke anion derivatives and homobinuclear complexes as tectons in designing heteropolymetallic systems
No full textCucos A, Avarvari N, Andruh M, Journaux Y, Müller A, Schmidtmann M. Reinecke anion derivatives and homobinuclear complexes as tectons in designing heteropolymetallic systems. EUROPEAN JOURNAL OF INORGANIC CHEMISTRY. 2006;2006(5):903-907
Spin-dependent electrochemistry and electrochemical enantioselective recognition with chiral methylated bis(ethylenedithio)-tetrathiafulvalenes
No full text: Enantio-discrimination and spin-dependent electrochemistry (SDE), as a manifestation of the chirality-induced spin selectivity (CISS) effect, are important phenomena that can be probed by "chiral" electrochemistry. Here, we prepared chiralized surfaces of gold and nickel, to serve as working electrodes, through effective chemisorption of enantiopure dimethyl-bis(ethylenedithio)-tetrathiafulvalene (DM-BEDT-TTF) 1, tetramethyl-bis(ethylenedithio)-tetrathiafulvalene (TM-BEDT-TTF) 2, and their capped silver nanoparticle (AgNPs) aggregate by simple incubation of the metallic substrates. The effective chemisorption was checked by means of ultrahigh vacuum x-ray photoelectron spectroscopy (XPS) and by electro-desorption experiments, i.e., cyclic voltammetry (CV) scans showing a first electro-desorption peak at about -1.0 V. The Au|1 and Au|2 chiral electrodes were successfully used in CV experiments exploiting chiral redox probes. Finally, the hybrid interfaces Ni|enantiopure 1 or 2|AgNPs served as working electrodes in SDE experiments. In particular, the hybrid chiral interfaces Ni|(R)-2|AgNPs and Ni|(S)-2|AgNPs exhibited a significant spin-filtering ability, as a manifestation of the CISS effect, with average spin polarization values of 15%
Radical Cation Salts of Tetramethyltetrathiafulvalene (TM-TTF) and Tetramethyltetraselenafulvalene (TM-TSF) with Chlorocyananilate-Based Anions
No full textElectrocrystallization of tetramethyltetrathiafulvalene (TM-TTF) and tetramethyltetraselenafulvalene (TM-TSF) with chlorocyananilate monoanion or/and tris(chlorocyananilato)ferrate(III) in THF/DCM solvent mixtures yielded a salt formulated as [TM-TTF]4[K(HClCNAn)4] (1) with the former and π-d hybrid systems, formulated as [TM-TTF]5[Fe(ClCNAn)3]·2CH2Cl2 (2) and [TM-TSF]3[Fe(ClCNAn)3]·0.5CH2Cl·2.5H2O (3), respectively, with the latter. Compound 1 shows segregation of TM-TTF donor molecules and K(HClCNAn)4 anionic clusters in the bc plane. The donor molecules are present as mixed-valence dimers and show a β′ packing arrangement. Compounds 2 and 3 consist of hybrid organic/inorganic structures with no segregation of [Fe(ClCNAn)3]3- anionic complexes and organic TM-TTF/TM-TSF donors. In the structure of compound 3, TM-TSF dimers are trapped between anilate units of metal complexes of opposite chirality. Furthermore, tetrameric donor motifs and solvent molecules of crystallization complete the structure. Single-crystal conductivity measurements on compounds 1 and 2 show semiconducting behavior with room-temperature conductivity values of 5 × 10-5 and 2 × 10-4 10 S cm-1 and activation energies of 1960 and 1900 K, respectively. Under high pressure, compound 2 remains a semiconductor, yet its room-temperature conductivity value strongly increases up to 0.2 S cm-1 at 9.8 GPa
Chiral Molecular Recognition Trends In Aromatic And Helical Systems Revealed With Rotational Spectroscopy
No full text"The rules of engagement for chiral molecules have evolved beyond the static ""three-point"" interaction picture. Models where weak intermolecular interactions compete and have a decisive act in establishing the molecular fit are the new travel guides to molecular recognition.\footnote{A. Zehnacker, M. Suhm. {\it Angew. Chem. Int. Ed.} 47, 6970–6992 (2008).} Moreover, molecules with dominant aromatic substructure foresee more unconventional intermolecular contact schemes given their delocalized electron distribution. This notion is valid for planar and helical motifs, as is the case of the smallest polycyclic aromatic hydrocarbon with a screw sense, tetrahelicene.\footnote{S.R. Domingos, K. Martin, N. Avarvari, M. Schnell. {\it Angew. Chem. Int. Ed.} 58, 11257–11261 (2019).} Given their compatibility with theoretical calculations, studies of cluster formation in the gas phase are pertinent approaches to disclose the ruling intermolecular forces at play and their role mediating molecular recognition.\footnote{S.R. Domingos, C. P\'{e}rez, N.M. Kreienborg, C. Merten, M. Schnell. {\it Commun. Chem.} accepted (2021).} In this scope, broadband rotational spectroscopy experiments are ongoing, and we will discuss our latest insights from studies on planar and helical aromatic systems."Made available in DSpace on 2021-09-24T21:09:35Z (GMT). No. of bitstreams: 2
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Charge transfer complexes and radical cation salts of chiral methylated organosulfur donors
No full textThe single crystal X-ray structure of the all-axial conformer of the (R,R,R,R) enantiomer of the chiral donor tetramethyl-BEDT-TTF (TM-BEDT-TTF) was described and compared to the all-equatorial conformer. (S,S,S,S)-Tetramethyl-BEDT-TTF formed crystalline 1 : 1 complexes with TCNQ and TCNQ-F4, as well as a THF solvate of the TCNQ complex. Donors bis((2S,4S)-pentane-2,4-dithio)tetrathiafulvalene and (ethylenedithio)((2S,4S)-pentane-2,4-dithio)tetrathiafulvalene, which contain seven-membered rings bearing chirally oriented methyl groups, only formed complexes with TCNQ-F4. The TCNQ-F4 complexes contain planar organosulfur systems, in contrast to the TCNQ complexes in which there is minimal charge transfer. A variety of crystal packing modes were observed. Electrocrystallization experiments with both enantiomers and the racemic form of tetramethyl-BEDT-TTF afforded mixed valence radical cation salts with the AsF6 and SbF6 anions formulated as (TM-BEDT-TTF)2XF6 (X = As, Sb). Electrical conductivity was only found in one charge transfer complex, while the radical cation salts are all semiconducting
Combined Experimental/Theoretical Study on the Luminescent Properties of Homoleptic/Heteroleptic Erbium(III) Anilate-Based 2D Coordination Polymers
No full textThe synthesis, structural and photophysical characterization, and theoretical studies on homo/heteroleptic neutral 2D-layered coordination polymers (CPs), obtained by combining the ErIII ion with chlorocyananilate (ClCNAn) and/or tetrafluoroterephthalate (F4BDC) linkers, are herein reported. The structure of the heteroleptic ErIII-based CP, formulated as [Er2(ClCNAn)2(F4BDC)(DMSO)6]n (1) is also reported. 1 crystallizes in the triclinic P1 ̄ space group, and the structure consists of neutral 2D layers formed by ErIII 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
Nouveaux Complexes Organométalliques à base de Métaux des Groupes 3 et 13 pour la Polymérisation d'Esters Cycliques
No full text(Jury : C. Darcel, N. Avarvari, M. Etienne, R. Gauvin, C. Thomas , J.-F. Carpentier)Thèse de Doctorat de l'Université de Rennes
Thiophene-benzoquinones: synthesis, crystal structures and preliminary coordination chemistry of derived anilate ligands
No full text2,5-Bis(thiophene) and 2,5-bis(ethylenedioxy-thiophene) (EDOT) derivatives of 3,6-diethoxy-1,4-benzoquinone (para isomers) were prepared by Stille coupling between the 2,5-dibromo-3,6-diethoxy-1,4-benzoquinone precursors and (n-Bu)(3)Sn-R (R = 2-thiophenyl or 3,4-ethylenedioxy-2-thiophenyl) reagents. In a parallel series of experiments 2,6-bis(thiophene) and 2,6-EDOT-3,5-diethoxy-1,4-benzoquinone (meta isomers) were synthesized by the same strategy. The four compounds were structurally characterized. The thiophene derivatives show essentially planar conformation thanks to the conjugation and establishment of S center dot center dot center dot O 1,5-nonbonded interactions, while in the EDOT derivatives the thiophene moieties are twisted with respect to the benzoquinone ring because of the steric hindrance. TD-DFT calculations were performed on both para and meta thiophene isomers in order to explain the differences observed in the UV-Vis absorption spectra. The 2,5-derivatives are valuable precursors for thiophene containing anilate (An) ligands, as the first examples of electron rich substituent based anilates. The Cu(II) complex [Cu(Th(2)An)(tbbpy)]center dot 2H(2)O (Th(2)An = thiophene-anilate; tbbpy = 4,4\u27-bis(tert-butyl)-2,2\u27-bipyridine) was isolated and structurally characterized. The metal center lies within a square planar coordination geometry, while the ligands engage in a set of intermolecular contacts
Dysprosium Chlorocyanoanilate-Based 2D-Layered Coordination Polymers
No full textA series of two-dimensional (2D)-layered coordination polymers (CPs) based on the heterosubstituted anilate ligand ClCNAn2– derived from 3-chloro-6-cyano-2,5-dihydroxybenzoquinone and DyIII are reported. By changes in the synthetic methods (layering technique, solvothermal or conventional one-pot reactions) and conditions (solvent, concentration, etc.), different types of 2D extended networks could be prepared and structurally characterized. Compounds 1 and 1′, two polymorphs with the formula [Dy2(ClCNAn)3(DMSO)6]n·(H2O)x [x = 7 (1), 0 (1′)], were prepared by a conventional one-pot reaction and recrystallized at different concentrations. Compound 2, formulated as [Dy2(ClCNAn)3(DMF)6]n, was prepared by a layering technique, while compound 3, formulated as {(Me2NH2)2[Dy2(ClCNAn)4(H2O)2]·(DMF)2·(H2O)5}n, was obtained by a solvothermal method. Compounds 1 and 2 are neutral 2D CPs of the ClCNAn2– ligand and DyIII ions, while 3 presents 2D anionic layers of [Dy2(ClCNAn)4(H2O)2]2– alternating with cationic layers of Me2NH2+ ions. These compounds show very diverse networks, with compound 1 forming 2D (8,3) and (4,3) topology with eight- and four-membered rings with square cavities, 1′ and 2, respectively, a 2D (6,3) topology with six-membered rings (a rectangular cavity for 1′ and a regular hexagonal cavity for 2), and 3 a 2D (4,4) topology with distorted square cavities. In this respect, 1 and 1′ represent the first examples of polymorphism in the family of anilate-based CPs. Thermal analysis measurements (differential scanning calorimetry and thermogravimetry) show an exothermic polymorphic transformation from the kinetically stable 1′ phase to the thermodynamically stable phase 1. The magnetic behavior of 1–3 very likely indicates depopulation of the mJ levels, while the presence of weak antiferromagnetic coupling between the DyIII centers mediated by the anilate bridge cannot be excluded
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