EPR and ENDOR Study of a series of free base porphycenes in the photoexcited triplet state

Porphycene is a structural isomer of porphyrin. The photoexcited triplet states of porphycene, 2,7,12,17-tetra-n-propylporphycene and 9,10,19,20-tetra-n-propylporphycene in disordered solid solution were studied by EPR and ENDOR. The ENDOR spectra yield the hyperfine tensor elementsA zz for each of the different groups of equivalent protons. The dipolar contribution toA zz is estimated and spin densities are derived from the isotropic contribution. They are compared with results of all-valence-electrons self-consistent field molecular orbital calculations (RHF-INDO/SP and RHF-INDO/S).