EMISSION SPECTROSCOPIC PROPERTIES OF THE RED FORM OF DICHLORO(2,2'-BIPYRIDINE)PLATINUM(II) - ROLE OF INTERMOLECULAR STACKING INTERACTIONS

The structure of the red form of Pt(bpy)Cl-2 (bpy = 2,2'-bipyridine) h as been studied by variable-temperature X-ray crystallography. The sta ck of square-planar Pt(bpy)Cl-2 units in the linear-chain material con tracts with decreasing temperature; in the interval between 294 and 20 K, the platinum-platinum distance shortens from 3.449(1) to 3.370(2) Angstrom. Both absorption and emission spectra of the red compound dep end strikingly on temperature; as previously found for tetracyanoplati nate 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 line arly with the inverse cube of the metal-metal separation.