Investigations of the electronic structure and excited state processes of transition metal complexes with polypyridyl and Schiff base ligands

A detailed study of the emission and photophysics of late transition metal complexes as well as investigations of the role of pi-stacks in mediating electronic communication have been undertaken as a step towards the design of systems that will undergo photoinduced two electron transfer. Here we report investigations of the self-quenching and energy-transfer reactivity of a novel luminescent platinum(II) diimine complex, Pt(tmphen)(bdt) (tmphen=3,4,7,8-tetramethyl-1,10-phenanthroline, bdt=1,2-benzenedithiolate), using both time-resolved and steady-state emission spectroscopies. By simulating data according to analytical solutions derived for the lifetime and quantum yield, we have shown that the self-quenching reactivity can be described by the same model that is used to describe excimer formation in organic aromatic systems. In addition we have mapped out a narrow range of values for the kinetic parameters that describe self-quenching. We have also prepared binuclear rhenium and ruthenium complexes with bridging [2.2]paracyclophane diimine ligands as a means of probing the role of pi-stacks in facilitating electronic communication. From spectroscopic data and comproportionation constants we find relatively weak interactions mediated by the paracyclophane bridging group. To better understand the triplet excited states associated with the 2-pyridinecarboxaldimine (R-pyCa) Schiff base diimine ligands we have investigated the electronic structure of zinc(II) chloride complexes prepared with the R-pyCa ligands.