Synthesis, structures and properties of a new series of platinum–diimine–dithiolate complexes

The new square-planar platinum-diimine-dithiolate compounds [Pt(mesBIAN)SS] have been synthesised {mesBIAN = bis(mesityl)biazanaphthenequinone; SS = 1,2-dithiooxalate (dto) , maleonitriledithiolate (mnt) , 1,2-benzenedithiolate (bdt) , 3,4-toluenedithiolate (tdt) and 1,3-dithia-2-thione-4,5-dithiolate (dmit) }, and the X-ray crystal structures of and determined. Cyclic voltammetry reveals that all the compounds form stable anions, and ESR spectroscopy of these anions shows that the SOMO is based upon the mesBIAN ligand; compounds also show a reversible oxidation wave in their CV. Computational studies reveal that charge-transfer processes from orbitals that are combinations of metal and dithiolate ligand to a mesBIAN pi-based LUMO are responsible for the low energy absorptions seen in the UV/visible spectra of these compounds, and that the reverse process is responsible for the observed room-temperature solution luminescence of [Pt(mesBIAN)Cl(2)] and , and . Compounds and , containing aromatic thiolates, were not found to luminesce under the same conditions. Resonance Raman experiments have shown the origin of band-broadening of the lowest-energy absorption band in the absorption spectra of to be due to vibronic structure within one electronic transition.