Redox multifunctionality in a series of Pt(II) dithiolene complexes of a tetrathiafulvalene-based diphosphine ligand.

The redox-active and chelating diphosphine, 3,4-dimethyl-3',4'-bis(diphenylphosphino)-tetrathiafulvalene, denoted as P2, is engaged in a series of platinum complexes, [(P2)Pt(dithiolene)], with different dithiolate ligands, such as 1,2-benzenedithiolate (bdt), 1,3-dithiole-2-thione-4,5-dithiolate (dmit), and 5,6-dihydro-1,4-dithiin-2,3-dithiolate (dddt). The complexes are structurally characterized by X-ray diffraction, together with a model compound derived from bis(diphenylphosphino)ethane, namely, [(dppe)Pt(dddt)]. Four successive reversible electron-transfer processes are found for the [(P2)Pt(dddt)] complex, associated with the two covalently linked but electronically uncoupled electrophores, that is, the TTF core and the platinum dithiolene moiety. The assignments of the different redox processes to either one or the other electrophore is made thanks to the electrochemical properties of the model compound [(dppe)Pt(dddt)] lacking the TTF redox core, and with the help of theoretical calculations (DFT) to understand the nature and energy of the frontier orbitals of the [(P2)Pt(dithiolene)] complexes in their different oxidation states. The first oxidation of the highly electron-rich [(P2)Pt(dddt)] complex can be unambiguously assigned to the redox process affecting the Pt(dddt) moiety rather than the TTF core, a rare example in the coordination chemistry of tetrathiafulvalenes acting as ligands.

Heteroleptic binuclear palladium(II) and platinum(II) complexes containing 1,2-bis(diphenylphosphino)acetylene and 1,2-benzenedithiolates: syntheses, crystal structures, electrochemistry and photoluminescence properties.

A series of heteroleptic binuclear Pd(ii) and Pt(ii) complexes, [M(bdts)](2)(micro-dppa)(2) (M = Pd () and Pt (); dppa = 1,2-bis(diphenylphosphino)acetylene = Ph(2)PC[triple bond, length as m-dash]CPPh(2); bdts = 1,2-benzenedithiolate (bdt: a), 3,4-toluenedithiolate (tdt: b) and 1,4-dichloro-2,3-benzenedithiolate (Cl(2)bdt: c), containing two square-planar MP(2)S(2) cores were prepared using (MCl(2))(2)(micro-dppa)(2) (M = Pd () and Pt ()) and the corresponding 1,2-benzenedithiols, and characterized by spectroscopic methods including FT-IR, Raman, UV-vis, MALDI-TOF-MS, (31)P{(1)H} and/or (195)Pt{(1)H} NMR spectroscopy. X-Ray crystal structure analyses for complexes and revealed that C1C2C4C3 is twisted in two ways with a torsion angle of 21.6-30.7 degrees for 3a, 4a, and 4b and about 42 degrees for 3c and 4c, and that their crystals are racemic mixtures. Due to the more electronegative chloride atoms in the ligand, complexes and show higher nu(M-S) vibrational frequencies in their Raman spectra, smaller spin-spin coupling constants (J(Pt-P)) in their (195)Pt{(31)P} NMR spectra and higher anodic potentials (E(pa)) in their cyclic voltammograms than complexes 3a, 3b, 4a and 4b. Moreover, only complex containing the chlorinated ligand and Pt(ii) ion exhibits luminescence (lambda(ob) = 610 nm and lambda(ex) = 440 nm) in the solid state at 298 K. This emissive transition can be assigned as the d-pi(dithiolate) metal-to-ligand charge transfer (MLCT) and the feasibility of this spin-forbidden transition is ascribed to the effective spin-orbit coupling of ligand c containing heavy chloride atoms and the large spin-orbit coupling in Pt(ii).

Redox bifunctionality in a Pt(ii) dithiolene complex of a tetrathiafulvalene diphosphine ligand.

The Pt(ii) dithiolene complex of a tetrathiafulvalene diphosphine ligand exhibits two reversible redox systems at close potentials, localized on the weakly interacting TTF (tetrathiafulvalene) and Pt(dmit) moieties.