Mechanism of reaction of alkyl radicals with copper(II)(glycylglycylglycine) in aqueous solutions

The reactions of radical dotCH3 and radical dotCH2C(CH3)2OH with Cu(II)(GGG), GGG=glycylglycylglycine, in aqueous solutions were studied and compared with the analogous process for Cu(II)(glycine)2. The mechanism involves the following steps: Cu(II)L+radical dotR→LCu(III)R radical dotR+LCu(II)R→Cu(II)L+R2 LCu(III)R→(LCu(III)R′) The heterolysis of the Cu(III)CH3 bond for (Gly)2Cu(III)CH3 yields methane and Cu(III)(Gly)2 + whereas that for (GGG)Cu(III)CH3 yields Cu(I)(GGG) and methanol. The LCu(III)CH2C(CH3)2OH complexes decompose via LCu(III)CH2C(CH3)2OH→Cu(I)L+HOCH2C(CH3)2OH followed by Cu(I)L+LCu(III)CH2C(CH3)2OH→Cu(II)L+LCu(II)CH2C(CH3)2OH LCu(II)CH2C(CH3)2OH→Cu(II)L+CH2C(CH3)2+OH−. The complex (GGG)Cu(III)CH3 decomposes slowly, k=0.0035 s−1. Thus if analogous complexes are formed in biological systems they might react with other substrates present in the system yielding products which are deleterious to living species.