TEMPERATURE-DEPENDENT PHOTOLUMINESCENCE PROPERTIES OF TL[AG(CN)(2)] -FORMATION OF LUMINESCENT METAL-METAL-BONDED INORGANIC EXCIPLEXES IN THE SOLID-STATE

The photoluminescence behavior of single crystals of Tl[Ag(CN)(2)] has been studied as a. function of temperature. The 10 K spectra show a b road emission centered at about 420 nm and two excitation maxima at 30 1 and 314 nm. Exciting with each of these maxima gives a different tem perature dependence for the corresponding emission spectra. This resul t correlates with the crystal structure of the compound which indicate s the presence of two environments with Ag-Ag interactions. The fact t hat the emission band is largely red-shifted, broad, and structureless is consistent with exciplex emission. The results of extended Huckel and ab initio calculations indicate exciplex formation in the title co mpound. Our theoretical calculations show a deep potential well in the excited state with a Ag-Ag equilibrium distance of 2.45 Angstrom and a binding energy of 40.8 kcal/mol. The experimental and theoretical re sults in this study demonstrate the importance of excited-state Ag-Ag interactions leading to the formation of luminescent exciplexes in Tl[ Ag(CN)(2)]. To our knowledge, this is the first example of exciplex fo rmation between metal ions in the solid state for coordination compoun ds.