Quenching of the luminescence of singlet molecular oxygen by phthalocyanines and naphthalocyanines

A. A. Krasnovsky Jr., M. A. J. Rodgers, M. G. Galperin, M. E. Kenney, E. A. Lukjanetz

Center for Photochemical Sciences, Bowling Green State University, Bowling Green, Ohio, USA; *Institute of Organic Intermediates and Dyes, Moscow, 103787; Chemistry Department, Case Western Reserve University, Cleveland, Ohio, USA

Abstract: Using the direct measurement of the photosensitized luminescence of singlet molecular oxygen (1O2) the rate constants (kq) have been determined for 102 quenching by the following phthalocyanines and naphthalocyanines in chloroform: tetra-(4-tret-butyl) phthalocyanine (I), octa-(3,6-butoxy)-phthalocyanine (II), tetra-(6-tret-butyl)-2,3-naph-thalocyanine (III), aluminium tetra-(1-tert-phenyl)-2,3-naphthalocyanine (IV), tri-(n-hexylsiloxy)-derivatives of silicon-(V), tin-(VI), aluminium-(VII) and gallium-(VIII) 2,3-naphthalocyanme. The following kq values were obtained (kq10-8, M-s-1): 2.9 (I), 59 (II), 100 (III), 20 (IV), 3.9 (V), 53 (VI), 33 (VII), 110 (VIII). The data suggest that quenching by (I) is mostly caused by the formation of charge transfer complexes in collisions between 1O2 and the quencher. The energy transfer from 1O2 to the low-lying triplet states of the quenchers strongly contributes into 1O25 quenching by (II)(VIII). It was concluded that phthalocyanines and naphthalocyanines might be efficient inhibitors of photodestructive processes in photochemical and photobiological systems.

1 Permanent address: Department of Biology, Moscow State University, Moscow, 119899, USSR.

Russian Journal of Bioorganic Chemistry 1990, 16 (10):1413-1418

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