Synthesis, X-ray crystal structure and catalytic activity of the manganese(II) complex [Mn(bdoa)(H2O)3](bdoaH2 =benzene-1,2-dioxyacetic acid)

Benzene-1,2-dioxyacetic acid (bdoaH2) reacts with Mn(CH3CO2)2·4H2O in an ethanol-water mixture to give the manganese(II) complex [Mn(bdoa)(H2O)3]. The X-ray crystal structure of the complex shows the metal to be pseudo seven-coordinate. The quadridentate bdoa2− dicar☐ylate ligand forms an essentially planar girdle around the metal, being strongly bondedtransoid by a car☐ylate oxygen atom from each of the two car☐ylate moieties (mean MnO 2.199A˚) and also weakly chelated by the two internal ether oxygen atoms (mean MnO 2.413A˚). The coordination sphere about the manganese is completed by three water molecules (mean MnO 2.146A˚) lying in a meridional plane orthogonal to that of the bdoa2− ligand. Magnetic, conductivity and voltammetry data for the complex are given, and its use as a catalyst for the disproportionisation of H2O2 is described.

Structures, reactivity, and catalytic activity of dithiolato-bridged heterobimetallic MRh (M = Pt, Pd) complexes

Heterobimetallic complexes [(P−P)Pt(μ-S−S)Rh(cod)]ClO4 (P−P = (PPh3)2, Ph2P(CH2)3PPh2 (dppp), and Ph2P(CH2)4PPh2 (dppb); S−S = -S(CH2)2S- (EDT), -S(CH2)3S- (PDT), -S(CH2)4S- (BDT), cod = 1,5-cyclooctadiene) reacted with CO to form the carbonyl complexes [(P−P)Pt(μ-S−S)Rh(CO)2]ClO4 and then with PR3 ligands to give [(P−P)Pt(μ-S−S)Rh(CO)(PR3)]ClO4. The binuclear framework of these cod complexes was maintained in the reactions reported. The cod complexes were tested as catalyst precursors in the hydroformylation of styrene. HPNMR in situ studies showed that mononuclear species formed under catalytic conditions.

Binuclear and polymeric manganese(II) salicylate complexes: synthesis, crystal structure and catalytic activity of [Mn2(Hsal)4(H2O)4] and [{Mn2(sal)2(Hsal)(H2O)-(H3O)(py)4•2py}n](H2sal = salicylic acid, py = pyridine)

The two air-stable manganese(II) salicylate complexes [Mn2(Hsal)4(H2O)4]1 and polymeric [{Mn2(sal)2(Hsal)(H2O)(H3O)(py)4·2py}n]2(H2sal = salicylic acid and py = pyridine) have been synthesised easily, and their crystal structures determined. Both contain unsymmetrically bridging salicylate ligands. In the presence of added pyridine 1 and 2 vigorously catalyse the disproportionation of H2O2.

Enhancing the catalytic repertoire of nucleic acids: a systematic study of linker length and rigidity

The incorporation of potentially catalytic groups in DNA is of interest for the in vitro selection of novel deoxyribozymes, A series of 10 C5-modified analogues of 2'-deoxyuridine triphosphate have been synthesised that possess side chains of differing flexibility and bearing a primary amino or imidazole functionality, For each series of nucleotide analogues differing degrees of flexibility of the C5 side chain was achieved through the use of alkynyl, alkenyl and alkyl moieties, The imidazole function was conjugated to these CS-amino-modified nucleotides using either imidazole 4-acetic acid or imidazole 4-acrylic acid (urocanic acid), The substrate properties of the nucleotides (fully replacing dTTP) with Taq polymerase during PCR have been investigated in order to evaluate their potential applications for in vitro selection experiments, 5-(3-Aminopropynyl)dUTP and 5-(E-3-aminopropenyl)dUTP and their imidazole 4-acetic acid- and urocanic acid-modified conjugates were found to be substrates, In contrast, C5-amino-modified dUTPs with alkane or Z-alkene linkers and their corresponding conjugates were not substrates, The incorporation of these analogues during PCR has been confirmed by inhibition of restriction enzyme digestion using XbaI and by mass spectrometry of the PCR products.

Synthesis, structural characterization and catalytic activity of a multifunctional enzyme mimetic oxoperoxovanadium(v) complex

The synthesis and structural characterization of a novel oxoperoxovanadium(v) complex [VO(O-2)(PAH)-(phen)] containing the ligands 2-phenylacetohydroxamic acid (PAHH) and 1,10-phenanthroline (phen) has been accomplished. The oxoperoxovanadium(v) complex was found to mimic both vanadate-dependent haloperoxidase (VHPO) activity as well as nuclease activity through effective interaction with DNA. The complex is the first example of a structurally characterized stable oxoperoxovanadium(v) complex with a coordinated bi-dentate hydroximate moiety (-CONHO-) from 2-phenylacetohydroximate (PAH). The oxoperoxovanadium(v) complex has been used as catalyst for the peroxidative bromination reaction of some unsaturated alcohols (e.g. 4-pentene-1-ol, 1-octene-3-ol and 9-decene-1-ol) in the presence of H2O2 and KBr. The catalytic products have been characterized by GC-MS analysis and spectrophotometric methods. The DNA binding of this complex has been established with CT DNA whereas the DNA cleavage was demonstrated with plasmid DNA. The interactions of the complex with DNA have been monitored by electronic absorption and fluorescence emission spectroscopy. Viscometric measurements suggest that the compound is a DNA intercalator. The nuclease activity of this complex was confirmed by gel electrophoresis studies.

Cis–trans isomerism in diphenoxido bridged dicopper complexes: role of crystallized water to stabilize the cis isomer, variation in magnetic properties and conversion of both into a trinuclear species

The trans-[Cu2L2Cl2] (1), and cis-[Cu2L2Cl2]·H2O (2) isomers of a diphenoxido bridged Cu2O2 core have been synthesized using a tridentate reduced Schiff base ligand 2-[(2-dimethylamino-ethylamino)-methyl]-phenol. The geometry around Cu(II) is intermediate between square pyramid and trigonal bipyramid (Addison parameter, tau = 0.463) in 1 but nearly square pyramidal (tau = 0.049) in 2. The chloride ions are coordinated to Cu(II) and are trans oriented in 1 but cis oriented in 2. Both isomers have been optimized using density functional theory (DFT) calculations and it is found that the trans isomer is 7.2 kcal mol(-1) more favorable than the cis isomer. However, the hydrogen bonding interaction of crystallized water molecule with chloride ions compensates for the energy difference and stabilizes the cis isomer. Both complexes have been converted to a very rare phenoxido-azido bridged trinuclear species, [Cu3L2(mu(1,1)-N-3)(2)(H2O)(2)(ClO4)(2)] (3) which has also been characterized structurally. All the complexes are antiferromagnetically coupled but the magnitude of the coupling constants are significantly different (J = -156.60, -652.31, and -31.54 cm(-1) for 1, 2, and 3 respectively). Density functional theory (DFT) calculations have also been performed to gain further insight into the qualitative theoretical interpretation on the overall magnetic behavior of the complexes.

A rare case of solution and solid state inter-conversion of two copper(II) dimers and a copper(II) chain

Three Cu(II)-azido complexes of formula [Cu2L2(N-3)(2)] (1), [Cu2L2(N-3)(2)]center dot H2O (2) and [CuL(N-3)](n) (3) have been synthesized using the same tridentate Schiff base ligand HL (2-[(3-methylaminopropylimino)-methyl]-phenol), the condensation product of N-methyl-1,3-propanediamine and salicyldehyde). Compounds 1 and 2 are basal-apical mu-1,1 double azido bridged dimers. The dimeric structure of 1 is centro-symmetric but that of 2 is non-centrommetric. Compound 3 is a mu-1,1 single azido bridged 1D chain. The three complexes interconvert in solution and can be obtained in pure form by carefully controlling the synthetic conditions. Compound 2 undergoes an irreversible transformation to 1 upon dehydration in the solid state. The magnetic properties of compounds 1 and 2 show the presence of weak antiferromagnetic exchange interactions mediated by the double 1,1-N-3 azido bridges (J = -2.59(4) and -0.10(1) cm-(1), respectively). The single 1,1-N-3 bridge in compound 3 mediates a negligible exchange interaction.

Peroxidative bromination and oxygenation of organic compounds: synthesis, X-ray crystal structure and catalytic implications of mononuclear and binuclear oxovanadium(V) complexes containing Schiffbase ligands

Treatment of of (R,R)-N,N-salicylidene cyclohexane 1,2-diamine(H(2)L(1)) in methanol with aqueous NH(4)VO(3) solution in perchloric acid medium affords the mononuclear oxovanadium(V) complex [VOL(1)(MeOH)]-ClO(4) (1) as deep blue solid while the treatment of same solution of (R,R)-N,N-salicylidene cyclohexane 1,2-diamine(H(2)L(1)) with aqueous solution of VOSO(4) leads to the formation of di-(mu-oxo) bridged vanadium(V) complex [VO(2)L(2)](2) (2) as green solid where HL(2) = (R,R)-N-salicylidene cyclohexane 1,2-diamine. The ligand HL(2) is generated in situ by the hydrolysis of one of the imine bonds of HL(1) ligand during the course of formation of complex [VO(2)L(2)](2) (2). Both the compounds have been characterized by single crystal X-ray diffraction as well as spectroscopic methods. Compounds 1 and 2 are to act as catalyst for the catalytic bromide oxidation and C-H bond oxidation in presence of hydrogen peroxide. The representative substrates 2,4-dimethoxy benzoic acid and para-hydroxy benzoic acids are brominated in presence of H(2)O(2) and KBr in acid medium using the above compounds as catalyst. The complexes are also used as catalyst for C-H bond activation of the representative hydrocarbons toluene, ethylbenzene and cyclohexane where hydrogen peroxide acts as terminal oxidant. The yield percentage and turnover number are also quite good for the above catalytic reaction. The oxidized products of hydrocarbons have been characterized by GC Analysis while the brominated products have been characterized by (1)H NMR spectroscopic studies.

Complexes of palladium using di-2-pyridyl ketone as ligand: synthesis, structure and, spectral and catalytic properties

During the reaction of di-2-pyridyl ketone (dpk) with Na(2)[PdCl(4)] in alcoholic media, the C=O fragment of dpk undergoes facile solvolysis and the transformed di-2-pyridyl ketone (dpk(ROH), R = Me or H) binds to palladium as NN-donor. When the reaction is carried out in refluxing methanol, a mono-complex of type [Pd(dpk(MeOH))Cl(2)] is obtained. A similar reaction in ethanol affords a bis-complex of type [Pd(dpk(ROH))(2)]Cl(2). Structure of both the complexes have been determined by X-ray crystallography. In acetonitrile solution the [pd(dpk(MeOH))Cl(2)] and [pd(dpk(ROH))(2)]Cl(2) complexes show intense absorptions in the visible and ultraviolet region, origin of which has been probed through uvr calculations. These two palladium complexes are found to be efficient catalysts for Suzuki cross-coupling reactions.

High yield production of a soluble bifidobacterial β-galactosidase (BbgIV) inE. coliDH5α with improved catalytic efficiency for the synthesis of prebiotic galactooligosaccharides

The bifidobacterial β-galactosidase (BbgIV) was produced in E. coli DH5α at 37 and 30 °C in a 5 L bioreactor under varied conditions of dissolved oxygen (dO2) and pH. The yield of soluble BbgIV was significantly (P < 0.05) increased once the dO2 dropped to 0–2% and remained at such low values during the exponential phase. Limited dO2 significantly (P < 0.05) increased the plasmid copy number and decreased the cells growth rate. Consequently, the BbgIV yield increased to its maximum (71–75 mg per g dry cell weight), which represented 20–25% of the total soluble proteins in the cells. In addition, the specific activity and catalytic efficiency of BbgIV were significantly (P < 0.05) enhanced under limited dO2 conditions. This was concomitant with a change in the enzyme secondary structure, suggesting a link between the enzyme structure and function. The knowledge generated from this work is very important for producing BbgIV as a biocatalyst for the development of a cost-effective process for the synthesis of prebiotic galactooligosaccharides from lactose.

Genetic evidence for a predominant role of PI3Kβ catalytic activity in ITAM- and integrin-mediated signaling in platelets.

Phosphatidylinositol 3-kinase (PI3K) isoforms PI3Kbeta and PI3Kgamma are implicated in platelet adhesion, activation, and aggregation, but their relative contribution is still unclear or controversial. Here, we report the first comparative functional analysis of platelets from mice expressing a catalytically inactive form of PI3Kbeta or PI3Kgamma. We demonstrate that both isoforms were similarly required for maximal activation of the small GTPase Rap1b and for complete platelet aggregation upon stimulation of G protein-coupled receptors for adenosine 5'-diphosphate (ADP) or U46619. Their contribution to these events, however, was largely redundant and dispensable. However, PI3Kbeta, but not PI3Kgamma, enzymatic activity was absolutely required for Akt phosphorylation, Rap1 activation, and platelet aggregation downstream of the immunoreceptor tyrosine-based activation motif (ITAM)-bearing receptor glycoprotein VI (GPVI). Moreover, PI3Kbeta was a major essential regulator of platelet adhesion to fibrinogen and of integrin alpha(IIb)beta(3)-mediated spreading. These results provide genetic evidence for a crucial and selective role of PI3Kbeta in signaling through GPVI and integrin alpha(IIb)beta(3).