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Three phenols with pendant, hydrogen-bonded bases (HOAr-B) have been oxidized in MeCN with various one-electron oxidants. The bases are a primary amine (-CPh(2)NH(2)), an imidazole, and a pyridine. The product of chemical and quasi-reversible electrochemical oxidations in each case is the phenoxyl radical in which the phenolic proton has transferred to the base, (*)OAr-BH(+), a proton-coupled electron transfer (PCET) process. The redox potentials for these oxidations are lower than for other phenols, predominately from the driving force for proton movement. One-electron oxidation of the phenols occurs by a concerted proton-electron transfer (CPET) mechanism, based on thermochemical arguments, isotope effects, and DeltaDeltaG(++)/DeltaDeltaG degrees . The data rule out stepwise paths involving initial electron transfer to form the phenol radical cations [(*)(+)HOAr-B] or initial proton transfer to give the zwitterions [(-)OAr-BH(+)]. The rate constant for heterogeneous electron transfer from HOAr-NH(2) to a platinum electrode has been derived from electrochemical measurements. For oxidations of HOAr-NH(2), the dependence of the solution rate constants on driving force, on temperature, and on the nature of the oxidant, and the correspondence between the homogeneous and heterogeneous rate constants, are all consistent with the application of adiabatic Marcus theory. The CPET reorganization energies, lambda = 23-56 kcal mol(-)(1), are large in comparison with those for electron transfer reactions of aromatic compounds. The reactions are not highly non-adiabatic, based on minimum values of H(rp) derived from the temperature dependence of the rate constants. These are among the first detailed analyses of CPET reactions where the proton and electron move to different sites.

A series of copper(II) complexes with tripodal polypyridylmethylamine ligands, such as tris(2-pyridylmethyl)amine (tpa), ((6-methyl-2-pyridyl)methyl)bis(2-pyridylmethyl)amine (Me(1)tpa), bis((6-methyl-2-pyridyl)methyl)(2-pyridylmethyl)amine (Me(2)tpa), and tris((6-methyl-2-pyridyl)methyl)amine (Me(3)tpa), have been synthesized and characterized by X-ray crystallography. [Cu(H(2)O)(tpa)](ClO(4))(2) (1) crystallized in the monoclinic system, space group P2(1)/a, with a = 15.029(7) Å, b = 9.268(2) Å, c = 17.948(5) Å, beta = 113.80(3) degrees, and Z = 4 (R = 0.061, R(w) = 0.059). [CuCl(Me(1)tpa)]ClO(4) (2) crystallized in the triclinic system, space group P&onemacr;, with a = 13.617(4) Å, b = 14.532(4) Å, c = 12.357(4) Å, alpha = 106.01(3) degrees, beta = 111.96(2) degrees, gamma = 71.61(2) degrees, and Z = 4 (R = 0.054, R(w) = 0.037). [CuCl(Me(2)tpa)]ClO(4) (3) crystallized in the monoclinic system, space group P2(1)/n, with a = 19.650(4) Å, b = 13.528(4) Å, c = 8.55(1) Å, beta = 101.51(5) degrees, and Z = 4 (R = 0.071, R(w) = 0.050). [CuCl(Me(3)tpa)][CuCl(2)(Me(3)tpa)]ClO(4) (4) crystallized in the monoclinic system, space group P2(1)/a, with a = 15.698(6) Å, b = 14.687(7) Å, c = 19.475(4) Å, beta = 97.13(2) degrees, and Z = 4 (R = 0.054, R(w) = 0.038). All the Cu atoms of 1-4 have pentacoordinate geometries with three pyridyl and one tertiary amino nitrogen atoms, and a chloride or aqua oxygen atom. Nitrite ion coordinated to the Cu(II) center of Me(1)tpa, Me(2)tpa, and Me(3)tpa complexes with only oxygen atom to form nitrito adducts. The cyclic voltammograms of [Cu(H(2)O)(Me(n)()tpa)](2+) (n = 0, 1, 2, and 3) in the presence of NO(2)(-) in H(2)O (pH 7.0) revealed that the catalytic activity for the reduction of NO(2)(-) increases in the order Me(3)tpa << Me(2)tpa << Me(1)tpa < tpa complexes.

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A carbonyl ligand of [Ru(bpy)2(CO)2]( 6>2 (1) (bpy = 2,2,-bipyridine) or [Ru(bpy)(trpy)(CO)](PF6)2 (2) (trpy = 2,2':6',2"-terpyridine) is reversibly converted to hydroxycarbonyl and r;1-C02 moieties by treatment with OH-. 1 and 2 also react with NaBH4 to afford CH3OH via formyl and hydroxymethyl complexes, and the molecular structures of 2 and [Ru(bpy)2(CO)(CH2OH)]PFé (3) were determined by X-ray structure analysis. Crystal data: 2, C26H1 9NsOP2Fi2Ru, monoclinic, space group C2/c, a = 34.683

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Static polarizabilities and hyperpolarizabilities have been calculated for the furan homologues including furan (C 4 H 4 O), thiophene (C 4 H 4 S), selenophene (C 4 H 4 Se), and tellurophene (C 4 H 4 Te), at the Hartree-Fock and various correlation levels by ab initio molecular orbital methods. The influence of substitution with heavy atoms on the molecular properties of the homologues was examined theoretically. In the calculations for molecules with Se and Te atoms, the contribution of core electrons in the atoms was estimated using effective core potential (ECP) methods. With the calculation for the thiophene molecule, effectiveness of the use of the ECP method was examined, and the ECP method was found to give the (hyper)polarizability values similar to those obtained considering all electrons for the molecule. The calculated results show that substitution of the heteroatom with heavy atoms systematically increases the individual components of the polarizability, R, and second hyperpolarizability, γ. On the other hand, this does not give systematic variations on the first hyperpolarizability, β. The variation of these values depending on the homologues was examined in terms of the perturbation expansion formula and was explained by the energy levels of the electronic excited states in the valence states. The second hyperpolarizability values calculated, including electron correlation effect, are well correlated with the observed electronic components of nonlinear optical susceptibilities, χ (3) , obtained using optical Kerr effect experiments, which have been done in our laboratory. However, some discrepancy is observed between the theoretical and the experimental values for the homologues with heavier heteroatoms. Possible causes for the discrepancy are discussed in detail. † Part of the special issue "Electronic and Nonlinear Optical Materials: Theory and Modeling".

Copper-nitrito and -nitro isomers, [Cu(ONO)(tpa)]PF6 and [Cu(NO2)(tpa)]PF6 (tpa = tris[(2-pyridyl)methyl]amine) were isolated and the molecular structures were determined by X-ray analysis. [Cu(ONO)(tpa)]PF6 (C18H18N5O2PF6Cu) crystallizes in the monoclinic space group P21/a with a = 13.374(2), b = 14.033(2), c = 13.455(2) Å, β = 119.10(1)°, V = 2206.5(6) Å3, and Z = 4. [Cu(NO2)(tpa)]PF6 (C18H18N5O2PF6Cu) crystallizes in the orthorhombic space group I/ba2 with a = 16.718(3), b = 17.554(3), c = 14.785(3) Å, V = 4338(1) Å3, and Z = 8. Those nitrito- and nitro-complexes exist as an equilibrium mixture in solutions. Electrochemical reduction of NO2− in the presence of [Cu(H2O)(tpa)](ClO4)2 at −0.4 V in H2O (pH 7.0) catalytically produced N2O with concomitant evolution of a small amount of NO via the nitro and nitrito adducts.