Variable magnetic interactions between S = 1/2 cation radical salts of functionalizable electron-rich dithiolene and diselenolene Cp2Mo complexes.

A series of Cp(2)Mo(dithiolene) and Cp(2)Mo(diselenolene) complexes containing N-alkyl-1,3-thiazoline-2-thione-4,5-dithiolate ligand (R-thiazdt, R = Me, Et, CH(2)CH(2)OH) and N-alkyl-1,3-thiazoline-2-thione-4,5-diselenolate ligand (R-thiazds, R = Me, Et) have been synthesized. These heteroleptic molybdenum complexes have been characterized by electrochemistry, spectroelectrochemistry, and single crystal X-ray diffraction. They act as very good electron donor complexes with a first oxidation potential 200 mV lower than in the prototypical Cp(2)Mo(dmit) complex and exhibit almost planar MoS(2)C(2) (or MoSe(2)C(2)) metallacycles. All five complexes formed charge transfer salts with a weak (TCNQ) and a strong acceptor (TCNQF(4)), affording ten different charge-transfer salts, all with 1:1 stoichiometry. Crystal structure determinations show that the S/Se substitution in the metallacycle systematically affords isostructural salts, while the Cp(2)Mo(R-thiazdt) complexes with R equals ethyl or CH(2)CH(2)OH can adopt different structures, depending on the involvement of the hydroxyl group into intra- or intermolecular hydrogen bonding interactions. Magnetic susceptibility data of the salts are correlated with their structural organization, demonstrating that a face-to-face organization of the Me-thiazdt (or Me-thiazds) ligand favors a strong antiferromagnetic interaction, while the bulkier R = Et or R = CH(2)CH(2)OH substituents can completely suppress such intermolecular interactions, with the added contribution of hydrogen bonding to the solid state organization.

Trithiaazafulvalene: a promising building block between tetrathiafulvalene and dithiadiazafulvalene.

[reaction: see text] New electroactive building blocks, the trithiaazafulvalenes (TTAFs), were synthesized. These redox-active molecules, intermediate between tetrathiafulvalene (TTF) and dithiadiazafulvalene (DTDAF), show promising features for the elaboration of molecular materials.

Unprecedented metal template effect on the coupling of dithiafulvene moieties.

Coordination of two dithiafulvenyldiphenylphosphines on a Mo(CO)(4) fragment allows a carbon-carbon bond formation upon oxidation, leading to a novel type of metallacycle substituted by a redox active vinylogous tetrathiafulvalene.

Vinylogous tetrathiafulvalene based podands: complexation interferences on the molecular movements triggered by electron transfer.

Substituted vinylogous tetrathiafulvalenes (TTFVs) containing two freely moving polyoxyethyl chains were prepared. Investigations of their redox behaviors in organic solvent show that these TTFV could efficiently complex metallic dications such as Pb(2+) or Ba(2+), leading to considerable modifications of their electrochemical response. As main feature, the molecule senses the association between the TTFV core and the metallic dication through a modification of the molecular motion triggered by the electron transfer. The complexation creates a link between the two parts of the TTFV core, causing considerable changes in the nature of the molecular motion. The resulting behavior is totally unusual as the 2-positively charged TTFV(2+) appears to present the highest association constants with the metallic dication.

Pyridyldithiafulvenes as precursors of coordination-driven self-assembled redox active macrocycle.

A novel redox active macrocycle including two vinylogous tetrathiafulvalenes (TTFVs) and two molybdenum tetracarbonyl fragments has been synthezised thanks to the coordination-driven self-assembly of complementary angular derivatives. Pyridyl vinylogous TTFVs have been deliberately elaborated for that purpose, using the oxidative coupling of pyridyldithiafulvenes (DTF). Cyclic voltammetry, IR and NMR spectroscopies, and single-crystal X-ray crystallography of the target molecules have been investigated.

Crown ether vinylogous tetrathiafulvalene receptors: complexation interference on the molecular movements triggered by electron transfer.

The synthesis of a series of crown ether substituted vinylogous tetrathiafulvalenes (TTFVs) has been carried out through oxidative coupling of bisdithiafulvenes. These new receptors have been fully characterized using electrochemical, spectroelectrochemical, and molecular modeling experiments. These studies show that, upon oxidation, either a clip movement (TTFVs 3a,b) or a stretch movement (TTFV 3c) occurs, depending on the length of the crown ether chains. Preliminary electrochemical studies, undertaken on TTFV 3c in dichloromethane, show a little shift of the first standard oxidation potential toward more positive values upon addition of the Pb(2+) ion, but a considerable variation of the electron-transfer kinetics. This result introduces an interesting concept for the preparation of sensors not based on thermodynamic variations but on kinetic modifications of the electron transfer.

Redox-active dithiafulvenyldiphenylphosphine as a mono- or bidentate ligand: intramolecular coupling reaction in the coordination sphere of a metal carbonyl fragment.

The coordinating ability of dithiafulvenyldiphenylphosphine (P-DTF) has been investigated with cis-W(CO)4(piperi-dine)2. As shown by the metal carbonyl complexes obtained, this redox-active vinylphosphine can act as a monodentate (P) and as a bidentate (P,S) ligand. Oxidation of cis-M(CO)4(P-DTF)2, M = Mo and W, leads to the carbon-carbon bond formation between the two coordinated dithiafulvenyldiphenylphosphines. This chemical coupling of the dithiafulvenyl cores in the coordination sphere of M(CO)4 (M = Mo, W) fragment has been studied in the presence of various oxidizing agents. The use of (BrC6H4)3NSbCl6 or AgBF4 induces the formation of a five-membered metallacycle with a vinylogous TTF backbone while DDQ leads to a six-membered metallacycle. The syntheses, crystal structures, and electrochemical properties of the complexes obtained are described.

Cyclic vinylogous TTF: a potential molecular clip triggered by electron transfer.

Cyclic vinylogous tetrathiafulvalenes (TTFs) where the two dithiole rings are linked through the outer sulfur atoms with an alkyl chain of various lengths were synthesized by oxidative intramolecular coupling of bis(dithiafulvenes). Upon oxidation, these systems exhibit large molecular movements associated with electron transfers. Their electrochemical behaviors were investigated together with the X-ray crystallographic structures of several derivatives and compared with molecular geometry calculations. Dependent on the length of the alkyl chain, either a stretch or a clip movement can be observed. These conformational modifications were found to be fast and fully reversible and required only low oxidation potentials. The movements seem to be almost insensitive to the nature of the substituents or its steric hindrance on the central conjugated spacer.