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 temp erature range 268-328 K in CDCl3 solution and at 11 K isolated in an A r matrix. The IVB shows resolved structure and a pronounced temperatur e 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 o ther is assumed to be slightly distorted. Piepho's MO treatment of mix ed-valence systems is generalized to the case of an unsymmetrical syst em. The parameters extracted from fits of the IVB clearly indicate tha t LuPc(2) is a delocalized system, i.e., ''Pc(1.5-)(Lu3+)Pc(1.5-)'', n ot ''Pc(2-)(Lu3+)Pc(. 1-), Pc(. 1-)(Lu3+)Pc(2-)''.