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 t he 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 oxyge n effect is observed. Flash photolysis and electron spin resonance (ES R) spectroscopy provide evidence for the formation of azide (N-3(.)) a nd ortho-phenylphenoxyl (OPP.) radicals. Cobalt(II) plays the role of a stabilizer for OPP. radicals. At high conversion, a brown precipitat e is formed. Various analytical results (high performance liquid chrom atography (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 obser ved as minor photoproducts. There is no formation of quinone derivativ es.