Dithiolene complexes as metallo-ligands: a crown-ether approach

International audienceA nickel dithiolene complex substituted with crown ether cyclic moieties incorporating four O atoms, abbreviated as [Ni(S2O4)2]1−,0, is isolated in its radical anionic (as Na+ salt) and neutral forms. The Na+ cation is six-coordinated with short Na[cdots, three dots, centered]O distances (2.46-2.52 Å), involving two crown ether moieties of two different complexes. The oxidized neutral complex [Ni(S2O4)2]0 was also isolated and structurally characterized. In the absence of alkaline cations during the synthesis, a mixed salt associating [Ni(S2O4)2]1− with Ni2+ was isolated, and formulated as (Ni,H2O)[Ni(S2O4)2]2, with the Ni2+ cation weakly bonded to two crown ether moieties. The salt exhibits an unprecedented solid state association with extremely short S[cdots, three dots, centered]S intermolecular contacts [3.332(2) Å], leading to a pairing of the radical [Ni(S2O4)2]− into antiferromagnetic uniform spin chains

Chiral electron-rich bis(cyclopentadienyl) dithiolene molybdenum complexes

International audienceEnantiomerically pure electron rich Cp2Mo(dithiolene) complexes have been synthesized from the enantiopure dithiolene ligands, namely the (R)- and the (S)-3(1-phenylethyl)-1,3-thiazoline-2-thione-4,5-dithiolate ligands. These heteroleptic molybdenum complexes act as very good electron donors, as demonstrated through electrochemical investigations. Both isomers form charge transfer salts with TCNQ with a 1:1 stoechiometry which have been characterized by single crystal X-ray diffraction, EPR and UV–vis spectroscopic investigations. Circular dichroism (CD) experiments were also carried out on the neutral (R) and (S) enantiomers as well as on the mono oxidized species of these Cp2Mo dithiolene complexes

Probing magnetic interactions in columnar phases of a paramagnetic gold dithiolene complex

International audienceA novel radical gold dithiolene complex exhibits a hexagonal columnar mesophase, as confirmed by optical microscopy , DSC analysis and X-ray diffraction . The extent of delocalization of the spin density in such a complex was analyzed by EPR . Temperature dependent magnetization measurements reveal that the global magnetic moment is remarkably affected at the liquid-crystalline phase transition with a marked hysteresis signature, rare behavior among the few described paramagnetic discotic phases. In addition, these molecules were found to strongly aggregate in solution into one-dimensional fibers with a mean diameter of 60 nm extending over micrometres, leading to the formation of gel-like structures. These fibers are stable and can be isolated on surfaces. The gelation of the system can also be detected by temperature-dependent magnetic measurements

A radical mixed-ligand gold bis(dithiolene) complex

International audienceA mixed-ligand bis(dithiolene) gold complex is isolated from scrambling reaction of two neutral radical symmetric complexes. Its asymmetric character translates into specific structural and electronic properties including larger electrochemical and optical band gaps than those of both precursors

Electronically coupled tetrathiafulvalene electrophores across a non-innocent acetylide-ruthenium bridge

International audienceThe synthesis and structural characterization of trans-[Ru(C≡CMe3TTF)2(dppe)2] (HC≡CMe3TTF = 4-ethynyl-4′,5,5′-trimethyltetrathiafulvalene) are described together with the X-ray crystal structures of the organic pro-ligands. Cyclic voltammetry experiments show sequential oxidation of the neutral compound with five one-electron processes up to the corresponding pentacation, trans-[Ru(III)(C≡CMe3TTF)2(dppe)2]5+, evidencing electronic interactions among the three coupled electrophores, the two TTFs and the Ru(II) center. A strong effect of the supporting electrolyte in dichloromethane was observed on the ΔE values especially between the second and third oxidation steps and between the third and fourth one, when [NBu4][PF6] was substituted for Na[B(C6H4(CF3)2)4]. This indicates the appreciable role ion-pairing interactions play in stabilizing these higher charge states, although solvation factors have been shown to be less significant in this case. The separation of the first two redox events was essentially independent of medium effects, indicating a more significant, inherent intramolecular electronic effect. The combined spectroscopic and computational investigations have evidenced that (i) the organic and the metal-based electroactive sites are strongly electronically coupled and (ii) the bisacetylide-ruthenium linker efficiently mediates electronic coupling between the two tetrathiafulvalenes

A Single-Component Molecular Metal Based on a Thiazole Dithiolate Gold Complex

International audienceA single component molecular conductor has been isolated from electrocrystallization of the monoanionic gold bis(dithiolene) complex based on the N-ethyl-1,3-thiazoline-2-thione-4,5-dithiolate (Et-thiazdt) ligand. The crystal structure of the system exhibits layers built from parallel uniform one-dimensional stacks of the planar molecule. At room temperature and ambient pressure the system is semiconducting (0.33 S·cm−1) with a small activation energy. However, the single crystal conductivity is strongly pressure dependent reaching 1000 S·cm−1 at 21 kbar. At 13 kbar there is a crossover between semiconducting and metallic regimes. Thus, the present system is the first well characterized single-component molecular metal without TTF dithiolate ligands. First-principles DFT calculations show that the ground state is antiferromagnetic with a very small band gap. A simulation of the effect of pressure on the electronic structure provides a rationale for the observed variations of the conductivity and gives insight on how to further stabilize the metallic state of the system

The radiolytic studies of panipenem in the solid state

The influence of ionizing radiation on the physicochemical properties of panipenem in solid state was studied. In the first part of our studies, we evaluated the possibility of applying radiosterilization to obtain sterile panipenem. Spectroscopic (FT-IR, Raman), chromatography (HPLC and HPLC-MS) and X-ray powder diffraction (XRPD) studies have shown that irradiation of ertapenem with the 25 kGy, the dose required to achieve sterility, does not change the physicochemical properties of the studied compound. The antimicrobial activity of panipenem irradiated with the dose of 25 kGy was reduced for three species. It was confirmed that the decrease in antimicrobial activity might be related to isomerization of panipenem