|Matthias Rank and Rainer F. Winter
Inorganic Chemistry, University of Konstanz, Universitätsstraße 10, 78464 Konstanz, Germany
Square-planar platinum complexes of the type (diimine)Pt(ER)2 (E = O, S) are an important class of sensitizers for the conversion of light into chemical or electrical energy. The basic idea of this work is to improve the efficiency of such sensitizers utilizing dye-functionalized donor ligands. The new square-planar platinum complexes 1, 2 and 3 with coumarins as "dye ligands" were prepared and their (spectro-)electrochemical properties were investigated.
UV/vis-spectroscopy and luminescence measurements showed that the luminescent 3MLCT-state is generated by irritation into the (ML)-L' CT-band of the complex as well as by irradiation into the π-π*-absorption band of the dye. This allows for a more efficient use of near UV/visible light for generating the charge separated state of the complexes. Experimental results are backed by quantum chemical calculations. The new coumarin dye 4 could also be synthesized and connected to a Pt-diimine moiety. Complex 5 shows improved absorbance and quantum yields.