Ph.D. UCLA, 1950
Mechanisms of Oxidation
Our group has been interested in the mechanisms of oxidations for over three decades. During the '70s, we examined the role of radical species, both free and metal-bound, in reactions between metal centers. During the '80s and '90s, we examined transformations of nickel (IV), cobalt (I), chromium (V), and chromium (IV). Present interests center about (a) reductions with unipositive indium, unipositive gallium, and dipositive germanium, and (b) the reactions of peroxynitrite.
We have generated aqueous solutions of In(I), Ge(II), and Ga(I) having much greater concentrations of these reductants than previously recorded and having substantially improved stability. Such solutions reduce complexes of cobalt (III), ruthenium (III), and iridium (IV) at rates which are sensitive to the nature of the ligands bound to the oxidizing center. These s-donor reductants may react either by 1 e- or 2 e- paths. We seek to define the factors which favor reduction my separable single-electron steps, to learn which ligating units allow effective inner-sphere bridging, and to determine how the reactivity of these donors compares with those exhibited by other oxo-acceptor species.
Most recently, we have prepared aqueous solutions of unipositive cadmium and found it to be dimeric. The equilibrium constant for disproportionation of Cd(I) to Cd(II) and Cd metal is estimated as 55 at 297 K, and its formal oxidation potential is -0.45 V.
Reactions of Peroxynitrite
The peroxynitrite anion (O=N-O-O-), which is formed in biosystems by the coupling of nitric oxide and superoxide, is a powerful oxidant. Transformations with external reductants are complicated by the decomposition of peroxynitrite to nitrate, particularly at low pH values. Interest is centered on the action of transition metal catalysis in altering the rates and modifying the selectivities of reactions with both inorganic and organic substrates. Conversions of 1 e- and 2 e- reductants are considered. Problems associated with maintaining effective concentrations of catalytic metal centers in media having high enough pH to allow survival of peroxynitrite have been addressed. We seek to expand the store of fundamental knowledge of this biologically ubiquitous and unusually reactive peroxo species.
Scholarly, Creative & Professional Activities
- Yang, Z. Y. & Gould, E. S. Molybdenum and copper catalysis of reductions by titanium(II) and titanium(III). Dalton Transactions, 396-398 (2006).
- Mukherjee, R., Yang, Z. Y. & Gould, E. S. Reductions by titanium(II) as catalyzed by titanium(IV). Dalton Transactions, 772-774 (2006).
- Yang, Z. Y. & Gould, E. S. Reductions by aquatitanium(II). Dalton Transactions, 1781-1784 (2005).
- Yang, Z. Y. & Gould, E. S. Electron transfer. Part 158. Reactions of octacyanomolybdate(V) and octacyanotungstate(V) with s(2) metal-ion reducing centers. Dalton Transactions, 1858-1861 (2004).
- Yang, Z. Y. & Gould, E. S. Electron transfer. Part 159. Reactions of tris(oxalato)cobaltate(III) with two-electron reductants. Dalton Transactions, 3601-3603 (2004).
- Babich, O. A. & Gould, E. S. Electron transfer. 157. Reactions of hypervalent manganese species with s(2) metal-ion reductants. Inorganic Chemistry 43, 1779-1783 (2004).
- Yang, Z. Y. & Gould, E. S. Reactions of 1,4-benzoquinones with s(2) reducing centers. Dalton Transactions, 2219-2223 (2003).
- Yang, Z. Y. & Gould, E. S. Reactions of vanadium(IV) and (V) with s(2) metal-ion reducing centers. Dalton Transactions, 3963-3967 (2003).
- Yang, Z. Y. & Gould, E. S. Electron transfer. 154. Reaction of the nitrosodisulfonate anion radical with one- and multi-electron inorganic reductants. Research on Chemical Intermediates 29, 181-189 (2003).
- Babich, O. A. & Gould, E. S. Electron transfer. 153. Internal electron transfer to bound cobalt(III) induced by hydroxyl radical. Research on Chemical Intermediates 29, 343-348 (2003).