ANALYSIS OF THE INTERVALENCE BAND IN LUTETIUM BIS(PHTHALOCYANINE) - THE SYSTEM IS DELOCALIZED

The intervalence band-(IVB) of LuPc(2) has been measured over the temperature range 268-328 K in CDCl3 solution and at 11 K isolated in an Ar matrix. The IVB shows resolved structure and a pronounced temperature dependence in CDCl3 solution. The various properties of the IVB are accounted for quite well if it is assumed that the system involves two conformers in equilibrium with an associated Delta H-o value of about 1000 cm(-1) One conformer is assumed to have D-4d symmetry, and the other is assumed to be slightly distorted. Piepho's MO treatment of mixed-valence systems is generalized to the case of an unsymmetrical system. The parameters extracted from fits of the IVB clearly indicate that LuPc(2) is a delocalized system, i.e., ''Pc(1.5-)(Lu3+)Pc(1.5-)'', not ''Pc(2-)(Lu3+)Pc(. 1-), Pc(. 1-)(Lu3+)Pc(2-)''.