AZIDOPENTAAMMINE COBALT(III) COMPLEX - A SELECTIVE PHOTOOXIDANT OF ORTHO-PHENYLPHENOL IN AQUEOUS-SOLUTION

Excitation of azidopentaammine cobalt(III) ([Co(NH3)(5)N-3](2+)), in the presence of or?ho-phenylphenol (OPP) in neutral solution, leads to the disappearance of OPP and the formation of Co(II). The presence of OPP does not affect the initial quantum yields significantly. No oxygen effect is observed. Flash photolysis and electron spin resonance (ESR) spectroscopy provide evidence for the formation of azide (N-3(.)) and ortho-phenylphenoxyl (OPP.) radicals. Cobalt(II) plays the role of a stabilizer for OPP. radicals. At high conversion, a brown precipitate is formed. Various analytical results (high performance liquid chromatography (HPLC), nuclear magnetic resonance (NMR) spectroscopy, mass specrometry) show that the ''para-para'' and ''ortho-ortho'' dimers of OPP are the major photoproducts. Trimers and tetramers are also observed as minor photoproducts. There is no formation of quinone derivatives.