Earlier Accounts have discussed the electrontransfer reduction of dioxygen (O 2 ), 1 the formation and reactivity of superoxide ion (O 2 •-), 2 and the nucleophilic character of hydroxide ion (HO -, Lewis base and one-electron reductant). 3 The first two describe the propensity of nucleophilic O 2 •-to disproportionate via Brønsted acids (HA, including H 2 O) to hydrogen peroxide (HOOH) and O 2 . The one-electron-reductant character of HOthat is discussed in the third led to the discovery of HO --induced reduction of (a) O 2 to O 2 •-, 4,5 (b) S 8 to S 3 •-, 6 anthraquinone (AQ) to AQ •-, 7 and (TPP)Fe III (py) 2 + (TTP ) tetraphenylporphyrin; py

Tridentate/tetradentate Schiff base ligands L(1) and L(2), derived from the condensation of o-vanillin or pyridine-2-aldehyde with N,N-dimethylethylenediammine, react with nickel acetate or perchlorate salt and azide, cyanate, or thiocyanate to give rise to a series of dinuclear complexes of formulas [Ni(L(1))(micro(1,1)-N(3))Ni(L(1))(N(3))(OH(2))].H(2)O (1), [[Ni(L(1))(micro(1,1)-NCS)Ni(L(1))(NCS)(OH(2))][Ni(L(1))(micro-CH(3)COO)Ni(L(1))( NCS) (OH(2))]] (2) [[2A][2B]], [Ni(L(1))(micro(1,1)-NCO)Ni(L(1))(NCO)(OH(2))].H(2)O (3), and [Ni(L(2)-OMe)(micro(1,1)-N(3))(N(3))](2) (4), where L(1) = Me(2)N(CH(2))(2)NCHC(6)H(3)(O(-))(OCH(3)) and L(2) = Me(2)N(CH(2))(2)NCHC(6)H(3)N. We have characterized these complexes by analytical, spectroscopic, and variable-temperature magnetic susceptibility measurements. The coordination geometry around all of the Ni(II) centers is a distorted octahedron with bridging azide, thiocyanate/acetate, or cyanate in a micro(1,1) mode and micro(2)-phenolate oxygen ion for 1-3, respectively, or with a double-bridging azide for 4. The magnetic properties of the complexes were studied by magnetic susceptibility (chi(M)) versus temperature measurements. The chi(M) nus T plot reveals that compounds 1 and 4 are strongly ferromagnetically coupled, 3 shows a weak ferromagnetic behavior, and 2 is very weakly antiferromagnetically coupled.

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