The high-spin dichloro Mn 2+ and Fe 2+ complexes of 4,11-dimethyl-1,4,8,11-tetraazabicyclo[6.6.2]hexadecane (1) and 4, 10-dimethyl-1,4,7,10-tetraazabicyclo[5.5.2]tetradecane (2) provide durable new compounds of these elements for important fundamental studies and applications. The compounds are especially noteable for their exceptional kinetic stabilities and redox activity. The X-ray crystal structures of all four complexes demonstrate that the ligands enforce a distorted octahedral geometry on the metals with two cis sites occupied by labile chloride ligands. Magnetic measurements reveal that all are high spin with typical magnetic moments. Cyclic voltammetry of the complexes shows reversible redox processes at +0.110 and +0.038 V (versus SHE) for the Fe 3+ /Fe 2+ couples of Fe(1)Cl 2 and Fe(2)Cl 2 , respectively, while the Mn 3+ /Mn 2+ and Mn 4+ /Mn 3+ couples were observed at +0.585 and +1.343 V, and +0.466 and +1.232 V for the complexes Mn(1)Cl 2 and Mn(2)Cl 2 , respectively. Mn 2+ (1) was found to react with H 2 O 2 and other oxidizing agents to produce the Mn 4+ (1) complex. The catalytic efficacy of Mn 4+ (1) in aqueous solution has been assessed in the epoxidation reaction of carbamazepine and hydrogen abstraction reaction with 1,4-cyclohexadiene. The complex has been found to be a selective catalyst, exhibiting moderate catalytic activity in oxygen transfer, but significantly more effective catalytic activity in hydrogen abstraction reactions.

A novel monomeric tetravalent manganese complex with the cross-bridged cyclam ligand 4,11-dimethyl-1,4,8,11-tetraazabicyclo[6.6.2]hexadecane (Me2EBC), [Mn(IV)(Me2EBC)(OH)2](PF6)2, was synthesized by oxidation of Mn(II)(Me2EBC)Cl2 with H2O2 in the presence of NH4PF6)in aqueous solution. The X-ray crystal structure determination of this manganese(IV) compound revealed that it contains two rare terminal hydroxo ligands. EPR studies in dry acetonitrile at 77 K show two broad resonances at g = 1.96 and 3.41, indicating that the manganese(IV) exists as a high-spin d3 species. Resonance Raman (rR) spectra of this manganese(IV) species reveal that the dihydroxy moiety, Mn(IV)(OH)2, is also the dominant species in aqueous solution (pH < 7). pH titration provides two pK(a) values, 6.86(4) and 10.0(1), associated with stepwise removal of the last two oxygen-bound protons from [Mn(IV)(Me2EBC)(OH)2](2+). The cyclic voltammetry of this manganese(IV) complex in dry acetonitrile at 298 K demonstrates two reversible redox processes at +0.756 and -0.696 V (versus SHE) for the Mn4+/Mn3+ and Mn3+/Mn2+ couples, respectively. This manganese(IV) complex is relatively stable in weak acidic aqueous solution but easily degrades in basic solution to manganese(III) derivatives with an 88 +/- 1% yield.

Background: Evaluate the potential role of p38 inhibitors for the treatment of osteoarthritis using an animal model of joint degeneration (iodoacetate-induced arthritis) and a pain model (Hargraeves assay).