Concerning the Triplet Energies of Non-metallated Phthalocyanines and the Mechanism of Singlet Oxygen (1Dg) - sensitized Phthalocyanine Luminescence

D. M. Baigel, A. A. Gorman,* I. Hamblett and T. J. Hill

Department of Chemistry, University of Manchester, Manchester M13 9PL, U. K.

Abstract: Establishment of equilibria for triplet energy transfer between singlet oxygen (1Dg), and both 2,3,9,10,16,17, 23,24-octahexadecyl- phthalocyanine (OHPC) and tetra-t-butylphthalocyanine (TBPC)

(a) demonstrates that the identical triplet energies of these non-metallated phthalocyanines, 22.8 ± 0.2 kcal mol-1, are very significantly less than hitherto thought and (b) provides strong support for a mechanism of 1Dg - sensitized phthalocyanine luminescence which involves triplet energy transfer fom 1Dg to the phthalocyanine triplet, these two species being the electronically excited components of a triplet energy transfer equilibrium.