Emission Spectroscopic Properties of the Red Form of Dichloro(2,2‘-bipyridine)platinum(II). Role of Intermolecular Stacking Interactions

Abstract

The structure of the red form of Pt(bpy)Cl 2 (bpy = 2,2‘-bipyridine) has been studied by variable-temperature X-ray crystallography. The stack of square-planar Pt(bpy)Cl 2 units in the linear-chain material contracts with decreasing temperature; in the interval between 294 and 20 K, the platinum−platinum distance shortens from 3.449(1) to 3.370(2) Å. Both absorption and emission spectra of the red compound depend strikingly on temperature; as previously found for tetracyanoplatinate salts, the emission maximum red-shifts as the temperature drops (613 nm at 300 K; 651 nm at 10 K), with the peak energy decreasing linearly with the inverse cube of the metal−metal separation.