Pyrazine-Coordinated Dinuclear and Mononuclear Ruthenium Complexes Formed via the Conversion of the Triply Chlorido-Bridged Diruthenium(II) Complex.

The pyrazine-coordinated dinuclear and mononuclear ruthenium complexes were synthesized through the framework conversion reactions of the triply chlorido-bridged diruthenium(II) complex [{RuII,II(bbpma)}2(µ-Cl)3]+ (bbpma; benzylbis(2-pyridylmethyl)amine, [1]+) in the presence of pyrazine, which could function as the simple molecular multinucleation ligand of metal compounds. A reduction reaction of fac-[RuIIICl3(bbpma)] with zinc in the presence of hydrochloric acid afforded [1]+ in solution, and the following addition of pyrazine (1 equiv) in the solution led to the formation of a singly pyrazine (pz)-bridged diruthenium complex, [{RuII,II(µ-Cl2ZnCl2)(bbpma)}2(µ-pz)] ([2(II,II)(ZnCl2)2]). The stoichiometric two-electron oxidation of [2(II,II)(ZnCl2)2] was successfully proceeded, and a Ru(III)-Ru(III) species, [{RuIII,IIICl2(bbpma)}2(µ-pz)](PF6)2 ([III,III](PF6)2), was isolated. The reaction of [1]+ with excess amounts of pyrazine without hydrochloric acid afforded mononuclear Ru(III) and Ru(II) complexes containing one or two pyrazine, fac-[RuClm(pz)3-m(bbpma)]+ (m = 2; [3]+; m = 1; [4]+). The details of the electrochemical and spectroscopic properties of [1]+-[4]+ in organic and aqueous solutions were discussed.

Ru(IV)-Ru(IV) complexes having the doubly oxido-bridged core with a bridging carbonato or hydrogencarbonato ligand.

Ru(IV)-Ru(IV) complexes having the doubly oxido-bridged diamond core with a bridging carbonato or hydrogencarbonato ligand, [{RuIV(ebpma)}2(µ-O)2(µ-O2CO(H)m)]Xn (ebpma; ethylbis(2-pyridylmethyl)amine, m = 0; [IV,IV]X2 (X = PF6, ClO4), m = 1; [IV,IV_1H](ClO4)3), were isolated via the oxidation of the corresponding carbonato-bridged Ru(III)-Ru(IV) complex ([III,IV]+), and "[IV,IV](ClO4)2 and [IV,IV_1H](ClO4)3" were structurally characterized. The electrochemical and spectroscopic properties of [IV,IV]2+ and [IV,IV_1H]3+ were investigated both in organic solvents and aqueous solutions. The reactivity toward organic solvents having (a) methyl group(s) and reactions with organic substrates were studied as well. This should be the first time when systematic comparisons of the Ru(IV)-Ru(IV) species and corresponding Ru(III)-Ru(IV) complexes in the same tridentate ligand system were made.

Recognition of d-Glucose in Water with Excellent Sensitivity, Selectivity, and Chiral Selectivity Using γ-Cyclodextrin and Fluorescent Boronic Acid Inclusion Complexes Having a Pseudo-diboronic Acid Moiety.

Fluorescence recognition of d-glucose in water with excellent sensitivity, selectivity, and chiral selectivity is desired because d-glucose is an essential component in biological and pathological processes. We report an innovative approach that exploits the 1:2 stoichiometric inclusion complexes of γ-cyclodextrin (γ-CyD) with two molecules of fluorescent monoboronic acid-based receptors, which form a pseudo-diboronic acid moiety as the recognition site for d-glucose in water. Two monoboronic acids (1F and 2N) were easily synthesized without heating or column purification. The 1:2 stoichiometric inclusion complexes (1F/γ-CyD and 2N/γ-CyD) were prepared in a mixture of dimethyl sulfoxide/water (2/98 in v/v) by mixing γ-CyD and the corresponding monoboronic acids. Both 1F/γ-CyD and 2N/γ-CyD exhibited strong turn-on response to d-glucose with excellent selectivity over nine other saccharides in the water-rich solvent at pH 7.4 owing to the ditopic recognition of d-glucose by the pseudo-diboronic acid moieties. The limits of detection of 1F/γ-CyD and 2N/γ-CyD for d-glucose were 1.1 and 1.8 µM, respectively, indicating the remarkable sensitivity for the detection of d-glucose at µM levels. 1F/γ-CyD and 2N/γ-CyD also demonstrated chiral-selective recognition of d-glucose, which is apparent from the 2.0- and 6.3-fold enhancement of fluorescence by the addition of d-glucose relative to l-glucose addition, owing to the chiral pseudo-diboronic acid moieties produced by the chiral γ-CyD cavity. To the best of our knowledge, 2N/γ-CyD has the highest d/l selectivity among hitherto reported fluorescent diboronic acid-based receptors.

Synthesis of Carbonato- and Doubly Oxido-Bridged Diruthenium(III,IV) Complex and Reactions with Cations.

Doubly oxido-bridged transition metal moieties, {M2(µ-O)2}, play important roles as oxidation reaction centers in nature. This work features a diruthenium(III,IV) complex with a doubly oxido-bridged core {Ru2III,IV(µ-O)2}3+ with a carbonato bridged between the two ruthenium centers, M[{RuIII,IV(ebpma)}2(µ-O)2(µ-O2CO)]2(PF6)3 (M[1CO3]2(PF6)3; Carbonato complex, ebpma; ethylbis(2-pyridymethyl)amine), and explores the interactions of this complex with cations (H+ and M+). M[1CO3]2(PF6)3 was formed via reactions of a singly oxido-bridged complex, [{RuIII,IVCl2(ebpma)}2(µ-O)]PF6·(CH3)2CO, with M2CO3 (M = K, Na) or with CO2(g), adjusted to around pH 12 with NaOH(aq.), in a water-acetone mixed solvent. The Carbonato complex was isolated as a powder in the form of M[1CO3]2(PF6)3 (M = K, Na), because of the interactions between the carbonato moiety and K+ or Na+ in the solid structure. In acidic aqueous solutions, unexpectedly, the carbonato ligand remained bound to the doubly bridged core, {Ru2III,IV(µ-O)2}3+ or {Ru2III,IV(µ-O)(µ-OH)}4+, without decarboxylation even under pH 1.0. Two-step one-protonation/deprotonation occurred reversibly between pH 1.0 and 13.2 to the bridging oxido and carbonato ligands. The structures of the corresponding one- and two-protonated complexes ([1CO3H]2+ and [1CO32H]3+) were successfully characterized.

N-C bond formation between two anilines coordinated to a ruthenium center in cis-form affording a 3,5-cyclohexadiene-1,2-diimine moiety.

Ruthenium complexes containing two anilines or its derivatives, cis-[RuII(NH2C6H5)2(bpy)2]2+ ([1]2+) and cis-[RuII(NH2C6H4(4-CH3))2(bpy)2]2+ ([2]2+), were oxidized by four molar equivalents of (NH4)4[CeIV(SO4)4]·2H2O to give N 1-phenylcyclohexa-3,5-diene-1,2-diimineruthenium(ii) complexes, cis-[RuII(NHC6H4 NC6H5)(bpy)2]2+ ([4]2+) and cis-[RuII(NHC6H3(4-CH3)NC6H4(4-CH3))(bpy)2]2+ ([5]2+), respectively, through an N-C bond formation between two aniline ligands cis-coordinated to the ruthenium center.

Preparation and antioxidant study of silver nanoparticles of Microsorum pteropus methanol extract.

This study reports a preparation of silver nanoparticles (SNPs) using Microsorum pteropus methanol extract, as a new approach in the development of therapeutic strategies against diseases caused by oxidative stress, reactive oxygen, and nitrogen species. During the effort of extraction and isolation from M. pteropus, X-ray single-crystal structural analysis of sucrose was succeeded. 1,1-Diphenyl-2-picrylhydrazyl (DPPH) and hydrogen peroxide scavenging assay were used to confirm the antioxidant potential. Preparation of SNPs was confirmed by ultraviolet-visible (UV-Vis) spectra with peaks between 431 and 436 nm. Infrared (IR) analysis showed OH, NH functional groups of alcohol, phenol, amine, and aliphatic CH stretching vibrations of hydrocarbon chains of the synthesized nanoparticles. The antioxidant properties of the SNPs significantly showed DPPH reduction with an IC50 value of 47.0 µg/mL and hydrogen peroxide scavenging activity with an IC50 value of 35.8 µg/mL, and hence, indicating their capability to eliminate potentially damaging oxidants involved in oxidative stress and their related diseases.

Framework Conversion of Oxido-Bridged Dinuclear Ruthenium Complexes.

Syntheses, properties, and reactions of hydroxido- or oxido-bridged dinuclear ruthenium complexes bearing a tridentate auxiliary ligand, ethylbis(2-pyridylmethyl)amine (ebpma) or benzylbis(2-pyridylmethyl)amine (bbpma), have been investigated. Reduction reactions of a singly oxido-bridged diruthenium complex bearing ebpma, [{RuIII,IVCl2(ebpma)}2(µ-O)]+ ([2Cl]+), by zinc in acetonitrile afforded an acetonitrile-substituted singly oxido-bridged complex in the RuIII-RuIII isovalent state, [{RuIII,IIICl(NCCH3)(ebpma)}2(µ-O)]2+ ([2CH3CN]2+). Chlorido ligand abstraction reactions using silver salts have also been attempted. Through a reaction of [2Cl]+ with two equimolar amounts of AgNO3 in water-acetone, a singly oxido-bridged complex having an aqua and a hydroxido, [{RuIIICl(OH2)(ebpma)}(µ-O){RuIVCl(OH)(ebpma)}]2+ ([2H2O-OH]2+), was obtained. Reactions with four equimolar amounts of AgL (L = CH3COO- or NO3-) in water-acetone gave doubly oxido- and bidentate oxygen donor ligand-bridged diruthenium complexes of Ru(III)-Ru(IV), [{RuIII,IV(ebpma)}2(µ-O)2(µ-L)]2+ ([3L]2+; L = O2CCH3; [3CH3COO]2+, L = O2NO; [3NO3]2+). Reactions of [3L]2+ under acidic conditions afforded a corresponding one-protonated species having the {Ru2(µ-O)(µ-OH)} core. Reactivity and electronic structure of the oxido-bridged diruthenium complexes were studied by electrochemical, spectroscopic, and theoretical methods.

Nitrosylruthenium Complexes as Polymerization Catalysts for Acrylonitrile in DMF.

Nitrosylruthenium complexes bearing two 2,2'-bipyridine (bpy) or 2-pyridinecarboxylate (pyc) ligands, [Ru(NO)X(bpy)2 ]3+ (X=CH3 CN, CH2 =CHCN, H2 O, Cl, ONO2 ) and [Ru(NO)(OH2 )(pyc)2 ]+ , were used as catalysts for the polymerization of acrylonitrile in N,N-dimethylformamide (DMF) under air without initiators to obtain polyacrylonitrile (PAN) with a high molecular weight and a narrow molecular weight distribution.