Stopped-flow kinetic studies of the reactions of [Fe2(BIPhMe)2(O2CH)4] (1a), where BIPhMe = 2,2‘-bis(1-methylimidazolyl)phenylmethoxymethane, and [Fe2(OH)(Me3TACN)2(OAc)2]+ (2a), where TACN = 1,4,7-trimethyl-1,4,7-triazacyclononane, with O2 are presented. In CHCl3, both reactions are first-order in [O2] and second-order in diiron(II) complex concentration. Mechanisms consistent with the kinetic data are proposed. The main feature of these schemes is a bimolecular pathway involving a tetranuclear (μ4-peroxo)diiron(II)diiron(III) species in the transition state. Evidence for carboxylate shifts in the oxidation mechanisms is presented, offering one possible way in which this class of structural equilibria might control the chemistry at related non-heme diiron centers in metalloproteins.

The excited state of the lf4,5,8-tetra-azaphenanthrene complex, [Ru(TAP)312+, which unlike [ R ~( p h e n ) ~] 2 + (phen = 1 ,lo-phenanthroline) or [Ru(bipy)#+ (bipy = 2,2'-bipyridyl) is strongly quenched upon binding to poly[d(G-C)], is found to be much more effective than either [Ru(phen)#+ or [ R ~( b i p y ) ~l z + in causing cleavage of the DNA backbone.

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