Geometric and electronic structure of [{Cu(MeAN)}2(μ-η2:η2(O2(2-)))]2+ with an unusually long O-O bond: O-O bond weakening vs activation for reductive cleavage.

Certain side-on peroxo-dicopper(II) species with particularly low ν(O-O) (710-730 cm(-1)) have been found in equilibrium with their bis-μ-oxo-dicopper(III) isomer. An issue is whether such side-on peroxo bridges are further activated for O-O cleavage. In a previous study (Liang, H.

New dicarboxylic acid bipyridine ligand for ruthenium polypyridyl sensitization of TiO2.

An ambidentate dicarboxylic acid bipyridine ligand, (4,5-diazafluoren-9-ylidene) malonic acid (dfm), was synthesized for coordination to Ru(II) and mesoporous nanocrystalline (anatase) TiO(2) thin films. The dfm ligand provides a conjugated pathway from the pyridyl rings to the carbonyl carbons of the carboxylic acid groups. X-ray crystal structures of [Ru(bpy)(2)(dfm)]Cl(2) and the corresponding diethyl ester compound, [Ru(bpy)(2)(defm)](PF(6))(2), were obtained.

Influence of ion pairing on the oxidation of iodide by MLCT excited states.

The oxidation of iodide to diiodide, I(2)˙(-), by the metal-to-ligand charge-transfer (MLCT) excited state of [Ru(deeb)(3)](2+), where deeb is 4,4'-(CO(2)CH(2)CH(3))(2)-2,2'-bipyridine, was quantified in acetonitrile and dichloromethane solution at room temperature. The redox and excited state properties of [Ru(deeb)(3)](2+) were similar in the two solvents; however, the mechanisms for excited state quenching by iodide were found to differ significantly. In acetonitrile, reaction of [Ru(deeb)(3)](2+*) and iodide was dynamic (lifetime quenching) with kinetics that followed the Stern-Volmer model (K(D) = 1.

Sulfur donor atom effects on copper(I)/O(2) chemistry with thioanisole containing tetradentate N(3)S ligand leading to μ-1,2-peroxo-dicopper(II) species.

To better understand the effect of thioether coordination in copper-O(2) chemistry, the tetradentate N(3)S ligand L(ASM) (2-(methylthio)-N,N-bis((pyridin-2-yl)methyl)benzenamine) and related alkylether ligand L(EOE) (2-ethoxy-N,N-bis((pyridin-2-yl)methyl)ethanamine) have been studied. The corresponding copper(I) complexes, [(L(ASM))Cu(I)](+) (1a) and [(L(EOE))Cu(I)](+) (3a), were studied as were the related compound [(L(ESE))Cu(I)](+) (2a, L(ESE) = (2-ethylthio-N,N-bis((pyridin-2-yl)methyl)ethanamine). The X-ray structure of 1a and its solution conductivity reveal a monomeric molecular structure possessing thioether coordination which persists in solution.

Reaction of Ru(II) diazafluorenone compound with nanocrystalline TiO2 thin film.

The Ru(II) compounds [Ru(bpy)(2)(mcbH)](2+) and [Ru(bpy)(2)(dafo)](2+), bpy is 2,2'-bipyridine where mcbH is 3-(CO(2)H)-2,2'-bipyridine and dafo is 4,5-diazafluoren-9-one, were synthesized, characterized, and anchored to nanocrystalline mesoporous TiO(2) thin films for excited state and interfacial electron transfer studies. X-ray crystallographic studies of [Ru(bpy)(2)(mcbH)](PF(6))(Cl) revealed a long Ru-N distance to the unsubstituted pyridine ligand of mcbH. Reaction of [Ru(bpy)(2)(dafo)](2+) with TiO(2) thin films resulted in interfacial chemistry.

Thioether S-ligation in a side-on micro-eta2:eta2-peroxodicopperii complex.

[(ANS)Cu(I)(CH(3)CN)](+) reacts with O(2) giving [{(ANS)Cu(II)}(2)(micro-eta(2):eta(2)-O(2)(2-))](2+), nu(O-O) = 731 cm(-1), shown to possess S-thioether ligation, based on comparisons with analogues having all N-ligands or a -S(Ph) group. The finding is a rare occurrence and new for side-on O(2)(2-) binding.

Copper(I)/O2 chemistry with imidazole containing tripodal tetradentate ligands leading to mu-1,2-peroxo-dicopper(II) species.

Cuprous and cupric complexes with the new imidazolyl containing tripodal tetradentate ligands {L(MIm), (1H-imidazol-4-yl)-N,N-bis((pyridin-2-yl)methyl)methanamine, and L(EIm), 2-(1H-imidazol-4-yl)-N,N-bis((pyridin-2-yl)methyl)ethanamine}, have been investigated to probe differences in their chemistry, especially in copper(I)-dioxygen chemistry, compared to that already known for the pyridyl analogue TMPA, tris(2-pyridyl)methyl)amine. Infrared (IR) stretching frequencies obtained from carbon monoxide adducts of [(L(MIm))Cu(I)](+) (1a) and [(L(EIm))Cu(I)](+) (2a) show that the imidazolyl donor is stronger than its pyridyl analogue. Electrochemical data suggest differences in the binding constant of Cu(II) to L(EIm) compared to TMPA and L(MIm), reflecting geometric changes.

Noncentrosymmetry in new templated gallium fluorophosphates.

Two new noncentrosymmetric polar gallium fluorophosphates have been synthesized under mild hydrothermal conditions through the use of enantiomorphically pure sources of either R-2-methylpiperazine or S-2-methylpiperazine. A centrosymmetric analogue was also prepared using a racemic source of the amine. Novel [Ga(3)F(PO(4))(4)](n)(4n-) layers, constructed from [Ga(3)O(3)F(PO(4))(4)] building units, are observed in all three compounds.

A peroxynitrite complex of copper: formation from a copper-nitrosyl complex, transformation to nitrite and exogenous phenol oxidative coupling or nitration.

Reaction of nitrogen monoxide with a copper(I) complex possessing a tridentate alkylamine ligand gives a Cu(I)-(*NO) adduct, which when exposed to dioxygen generates a peroxynitrite (O=NOO(-))-Cu(II) species. This undergoes thermal transformation to produce a copper(II) nitrito (NO(2) (-)) complex and 0.5 mol equiv O(2).

Photodriven spin change of Fe(II) benzimidazole compounds anchored to nanocrystalline TiO(2) thin films.

Ferrous tris-chelate compounds based on 2-(2'-pyridyl)benzimidazole (pybzim) have been prepared and characterized for studies of spin equilibria in fluid solution and when anchored to the surface of mesoporous nanocrystalline (anatase) TiO(2) and colloidal ZrO(2) thin films. The solid state structure of Fe(pybzim)(3)(ClO(4))(2).CH(3)CN.

Synthetic approaches for noncentrosymmetric molybdates.

The use of second-order Jahn-Teller active Mo (VI) centers and chiral organic amines is discussed as an approach to crystallographic noncentrosymmetry. Several series of reactions, conducted under mild hydrothermal conditions, were designed to probe important reaction variables. Correlations between reagent and solvent concentrations and the molybdate structure were investigated using composition space analysis, which allows for the isolation of specific reaction variables.

Copper-hydroperoxo-mediated N-debenzylation chemistry mimicking aspects of copper monooxygenases.

A substantial oxidative N-debenzylation reaction along with PhCHO formation occurs from a hydroperoxo-copper(II) complex that has a dibenzylamino substrate (N(CH 2Ph) 2 appended as a substituent on one pyridyl group of its tripodal tetradentate TMPA (also TPA, (2-pyridylmethyl)amine)) ligand framework. During the course of the (L (N(CH 2 ) (Ph) 2 ))Cu (II)( (-)OOH) reactivity, the formation of a substrate and a (-)OOH-derived (an oxygen atom) alkoxo Cu (II)( (-)OR) complex occurs. The observation that the same Cu (II)( (-)OR) species occurs from Cu (Iota)/PhIO chemistry suggests the possibility that a copper-oxo (cupryl) reactive intermediate forms during the alkoxo species formation; new ESI-MS data provide further support for this high-valent intermediate.

Reaction of a copper-dioxygen complex with nitrogen monoxide (*NO) leads to a copper(II)-peroxynitrite species.

A discrete peroxynitrite-copper(II) complex, [(TMG3tren)CuII(-OONO)]+ (3), has been generated in solution (ESI-MS, m/z = 565.15; tetragonal EPR) by reacting *NO(g) with superoxo complex [(TMG3tren)CuII(O2*-)]+ (2). Complex 3 undergoes a thermal transformation to give CuII-nitrite complex [(TMG3tren)CuII(-ONO)]+ (4) (X-ray) along with ca.

Copper dioxygen adducts: formation of bis(mu-oxo)dicopper(III) versus (mu-1,2)Peroxodicopper(II) complexes with small changes in one pyridyl-ligand substituent.

The preference for the formation of a particular Cu 2O 2 isomer coming from (ligand)-Cu (I)/O 2 reactivity can be regulated with the steric demands of a TMPA (tris(2-pyridylmethyl)amine) derived ligand possessing 6-pyridyl substituents on one of the three donor groups of the tripodal tetradentate ligand. When this substituent is an -XHR group (X = N or C) the traditional Cu (I)/O 2 adduct forms a (mu-1,2)peroxodicopper(II) species ( A). However, when the substituent is the slightly bulkier XR 2 moiety {aryl or NR 2 (R not equal H)}, a bis(mu-oxo)dicopper(III) structure ( C) is favored.

Suggestion of an organometallic intermediate in an intramolecular dechlorination reaction involving copper(I) and a ArCH2Cl moiety.

A copper(I)-mediated reductive dechlorination reaction involving an "internal" chloromethylene substrate at the pyridyl 6-position of one TMPA arm (TMPA triple bond TPA triple bond tris(2-pyridylmethyl)amine) leads to a 1:1 ratio of the starting ligand 6ClCH2-TMPA and a new methyl-TMPA product, 6CH2H-TMPA. On the basis of observed product distributions and a kinetic study, a reaction mechanism involving intramolecular oxidative insertion of Cu(I) to the C-Cl substrate is suggested. The resulting organometallic intermediate is then protonated, leading to the observed products.

[Mo16O53F2]12-: a new polyoxofluoromolybdate anion.

Single crystals of a new beta-octamolybdate salt containing protonated 1,4-diazabicyclo[2.2.2]octane cations were prepared under mild hydrothermal conditions.

A low-spin alkylperoxo-iron(III) complex with weak Fe-O and O-O bonds: implications for the mechanism of superoxide reductase.

The synthesis of a mononuclear, five-coordinate ferrous complex [([15]aneN4)FeII(SPh)](BF4) (1) is reported. This complex is a new model of the reduced active site of the enzyme superoxide reductase (SOR), which is comprised of a [(NHis)4(Scys)FeII] center. Complex 1 reacts with alkylhydroperoxides (tBuOOH, cumenylOOH) at low temperature to give a metastable, dark red intermediate (2a: R = tBu; 2b: R = cumenyl) that has been characterized by UV-vis, EPR, and resonance Raman spectroscopy.

An isolable, nonreducible high-valent manganese(V) imido corrolazine complex.

The manganese(V) imido complex [(TBP8Cz)Mn(V)(NMes)] (2) was synthesized from the Mn(III) complex [(TBP8Cz)Mn(III)] (1) and thermolysis of mesityl azide. An X-ray structure of 2 reveals a short Mn-N distance [1.595(4) A], consistent with the Mn-N triple bond expected for a manganese(V) imido species.

Directed synthesis of noncentrosymmetric molybdates using composition space analysis.

A systematic investigation of the factors governing the reaction product composition, hydrogen bonding, and symmetry was conducted in the MoO3/3-aminoquinuclidine/H2O system. Composition space analysis was performed through 36 individual reactions under mild hydrothermal conditions using racemic 3-aminoquinuclidine. Single crystals of three new compounds, [C7H16N2][Mo3O10] x H2O, [C7H16N2]2[Mo8O26] x H2O, and [C7H16N2]2[Mo8O26] x 4 H2O, were grown.

Triiodide quenching of ruthenium MLCT excited state in solution and on TiO2 surfaces: an alternate pathway for charge recombination.

The excited states of [Ru(bpy)2(deeb)](PF6)2, where bpy is 2,2-bipyridine and deeb is 4,4'-(CO2CH2CH3)2-2,2'-bipyridine, were found to be efficiently quenched by triiodide (I3-) in acetonitrile and dichloromethane. In dichloromethane, I3- was found to quench the excited states by static and dynamic mechanisms; Stern-Volmer analysis of the time-resolved and steady-state photoluminescence data produced self-consistent estimates for the I3- + Ru(bpy)2(deeb)2+ <==> [Ru(II)(bpy)2(deeb)2+,(I3-)]+ equilibrium, K = 51,000 M(-1), and the bimolecular quenching rate constant, kq = 4.0 x 10(10) M(-1) s(-1).

Selective DNA strand scission with binuclear copper complexes: implications for an active Cu2-O2 species.

A homologous series of binuclear copper(II) complexes [Cu(II)(2)(Nn)(Y)(2)](2+) (1-3) (n = 3-5 and Y = (ClO(4))(-) or (NO(3))(-)) were studied to investigate the intermediate(s) responsible for selective DNA strand scission in the presence of MPA/O(2) (MPA = 3-mercaptopropanoic acid). While the N3 complex does not react, the N4 and N5 analogues show comparable activity with strand scission occurring at a single-strand/double-strand junction. Identical reactivity is also observed in the alternate presence of H(2)O(2).

Second generation, orally active, antimalarial, artemisinin-derived trioxane dimers with high stability, efficacy, and anticancer activity.

In only two steps and in 63% overall yield, naturally occurring 1,2,4-trioxane artemisinin (1) was converted into C-10-carba trioxane conjugated diene dimer 4. This new dimer was then transformed easily in one additional 4 + 2-cycloaddition step into phthalate dimer 5, and further modification led to bis-benzyl alcohol dimer 7 and its phosphorylated analogues 8 and 9. Bis-benzyl alcohol dimer 7 is the most antimalarially active in vitro, 10 times more potent than artemisinin (1).

Copper-dioxygen adducts and the side-on peroxo dicopper(II)/bis(mu-oxo) dicopper(III) equilibrium: Significant ligand electronic effects.

The variation of ligand para substituents on pyridyl donor groups of tridentate amine copper(I) complexes was carried out in order to probe electronic effects on the equilibrium between mu-eta2:eta2-(side-on)-peroxo [Cu(II)2(O2(2-))]2+ and bis(mu-oxo) [Cu(III)2(O(2-))2] species formed upon reaction with O2. [Cu(I)(R-PYAN)(MeCN)n]B(C6F5)4 (R-PYAN = N-[2-(4-R-pyridin-2-yl)-ethyl]-N,N',N'-trimethyl-propane-1,3-diamine, R = NMe2, OMe, H, and Cl) (1R) vary over a narrow range in their Cu(II)/Cu(I) redox potentials (E(1/2) vs Fe(cp)2(+/0) = -0.40 V for 1(NMe2), -0.

Structure activity relationships of 5-, 6-, and 7-methyl-substituted azepan-3-one cathepsin K inhibitors.

The syntheses, in vitro characterizations, and rat and monkey in vivo pharmacokinetic profiles of a series of 5-, 6-, and 7-methyl-substituted azepanone-based cathepsin K inhibitors are described. Depending on the particular regiochemical substitution and stereochemical configuration, methyl-substituted azepanones were identified that had widely varied cathepsin K inhibitory potency as well as pharmacokinetic properties compared to the 4S-parent azepanone analogue, 1 (human cathepsin K, K(i,app) = 0.16 nM, rat oral bioavailability = 42%, rat in vivo clearance = 49.