Combining photosensitizers: The case of [Cl2Pt(bpym)Re(CO)3Cl] and its dithiolate analogs

Abstract

The bimetallic complex [Cl2Pt(bpym)Re(CO)3Cl] (4) (where bpym denotes 2,2′-bipyrimidine) has been prepared along with the corresponding monometallic precursors and the dithiolate derivatives with bdt2− (1,2-benzene-dithiolate) and mnt2− (1,2-maleonitrile-dithiolate). The compounds have been characterized using elemental analysis, NMR, FTIR, UV–Vis and cyclic voltammetry methods. DFT and TD-DFT calculations on all the complexes under study allow us to correlate geometries and electronic structures. The theoretical studies of the dithiolate bimetallic complexes assigned the main band in the UV–Vis spectrum as a mixed metal ligand to ligand charge transfer transition (MMLL′CT), analogous to [M(diimine)(dithiolate)] complexes, with the former red shifted due to the presence of the Re(CO)3Cl moiety. Moreover coordination of the dithiolate ligand to the bimetallic complex 4 influences not only the energy, but also the nature of HOMO orbital altering it from Re(CO)3Cl to Pt/bdt character.