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 (k_q) 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 k_q values were obtained (k_q·10^-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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