An electron spin resonance study of organomercury radical complexes with ortho-quinones and vitamin C

Photochemical and thermal reactions of ortho-quinones and organomercury lead to the formation of a series of quinine-HgR * radical complexes. Hyperfine splittings due to 199 Hg isotope were resolved for the 3,5-di-t-butylbenzoquinone complexes. Photochemical reactions of vitamin C in ethanol with a number of mercuric salts produce a paramagnetic intermediate which is assigned to the ion-pair involving the ascorbate radical anion and the mercuric ion. In di-n-butyl mercury, photolysis of vitamin C leads to the formation of a radical complex similar to those of quinine-HgR * but with a much smaller hyperfine coupling constant for 199 Hg. A simple theoretical model using some MO calculations on the π system of these organometal-quinone radical complexes, which include the metal atom, was developed to account for the systematic experimental observations.