Cis and trans-bis(tetrathiafulvalene-acetylide) platinum(ii) complexes: syntheses, crystal structures, and influence of the ancillary ligands on their electronic properties

Abstract

A series of four platinum(II) complexes bearing two tetrathiafulvalene acetylide ligands coordinated either cis or trans to the metal center are reported: cis-Pt(bipy)(CCMe₃TTF)₂, cis-Pt(tBu₂bipy)(CCMe₃TTF)₂, cis-Pt(dppe)(CCMe₃TTF)₂ and trans-Pt(PPh₃)₂(CCMe₃TTF)₂. The X-ray diffraction studies of the four complexes are reported and discussed. The electrochemical investigations carried out by cyclic voltammetry (CV) and differential pulse voltammetry (DPV) evidenced different redox behavior as a function of the ancillary ligand. Only for the cis-Pt(dppe)(CCMe₃TTF)₂ complex is the first oxidation wave resolved (ΔE = 70 mV) into two one-electron processes. Spectroelectrochemical investigations performed on the four complexes did not evidence any electronic interactions between the two organic electrophores. The splitting of the first oxidation wave observed in cis-Pt(dppe)(CCMe₃TTF)₂ is mainly explained by the non-equivalence of the two TTF moieties induced by the geometrical constraint imposed by the ancillary dppe ligand as found by density functional theory calculations.