[Quenching of the luminescence of singlet molecular oxygen by complexes of porphyrins and highly-charged metal ions].

Quenching of singlet oxygen luminescence by the complexes of tetraphenylporphin with Fe3+, Mn3+, Sn4+, and Al3+, synthetic dimer of TTP (mu-oxo-bis-FeTPP) and by Fe3+-meso-porphyrin-IX-dimethylester has been investigated. Quenching obeys the Stern - Folmer equation. The rate constants of 1O2 quenching (Kq) by monomeric Fe-Porphyrins correspond to 1-1.5 X 10(9) M-1.s-1 and do not depend on axial ligands bound to the metal (Cl-, CH3COO-, CNS-, pyridine). Dimerization decreases Kq down to 4 X 10(7) M-1.s-1.Kq of the complexes with Mn, Sn, and Al are equal to 2.5X10(8), 2X10(6), 10(7) M-1.s-1 respectively. The data suggest that quenching by the monomeric Fe- and, probably, Mn-porphyrins is due to energy transfer from 1O2 to the eta-d levels of the quenchers.