M. Sarakha et al., AZIDOPENTAAMMINE COBALT(III) COMPLEX - A SELECTIVE PHOTOOXIDANT OF ORTHO-PHENYLPHENOL IN AQUEOUS-SOLUTION, Journal of photochemistry and photobiology. A, Chemistry, 85(3), 1995, pp. 231-237
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.