Hybrid organic/inorganic complexes based on electroactive tetrathiafulvalene-functionalized diphosphanes tethered to C(3)-symmetrized Mo(3)Q(4) (Q = S, Se) clusters

Abstract

A two-step procedure for the preparation of hybrid complexes based on electroactive tetrathiafulvalene (TTF)- functionalized o-P(2) diphosphanes (o-P(2) = 3,4-dimethyl-3,4-bis(diphenylphosphino)tetrathiafulvalene) and inorganic C(3)-symmetrized Mo(3)Q(4) (Q = S, Se) clusters, namely, [Mo(3)S(4)Cl(3)(o-P(2))(3)]PF(6) ([1]PF(6)) and [Mo(3)Se(4)Cl(3)(o-P(2))(3)]PF(6) ([2]PF(6)), is reported. Their molecular and electronic structures are also described on the basis of X-ray diffraction experiments and density functional theory (DFT) calculations aimed at understanding the interactions established between both the organic and the inorganic parts. Cyclic voltammograms of compounds [1]PF(6) and [2]PF(6) display reduction features associated to the Mo(3)Q(4) core and oxidation characteristics due to the TTF skeleton. The oxidation chemistry of [1]PF(6) and [2]PF(6) in solution is also investigated by means of in situ electrospray ionization (ESI) mass spectrometry, UV-vis, and, electron paramagnetic resonance (EPR) measurements. Upon addition of increasing amounts of NOPF(6) (less than 3 equiv), the sequential formation of 1(n+) (n = 1-4) species was observed whereas addition of a 3-fold excess of NOPF(6) allows to access the three-electron oxidized [Mo(3)S(4)Cl(3)(o-P(2))(3)](4+) (1(4+)) and [Mo(3)Se(4)Cl(3)(o-P(2))(3)](4+) (2(4+)) cations. These 1(4+) and 2(4+) cations represent still rare examples of complexes with oxidized TTF-ligands that are remarkably stable either toward diphosphane dissociation or phosphane oxidation. Polycrystalline samples of compound [1](PF(6))(4) were obtained by oxidation of compound [1]PF(6) using NOPF(6) which were analyzed by solid state absorption, UV-vis, and Raman spectroscopies.