New open-framework phosphate and phosphite compounds of gallium

Five new open-framework compounds of gallium have been synthesized by hydrothermal methods and their structures determined by single crystal X-ray diffraction studies. The compounds, C8N4H26]Ga6F4(PO4)(6)], I, C5N3H11]Ga3F2(PO4)(3)]center dot H2O, II, C6N3H19]Ga-4(C2O4)(PO4)(4)(H2PO4)]center dot 2H(2)O, III, Ga2F3(HPO4)(PO4)]center dot 2H(3)O, IV, and C3N2H5](2)Ga-4(H2O)(3)(HPO3)(7)], V, possess three-dimensional structures. All the compounds are formed by the connectivity between the Ga polyhedra and phosphite/phosphate units. The observation of SBU-6 (I and II) and spiro-5 (IV) secondary building units (SBUs) are noteworthy. The flexibility of the formation of gallium phosphate frameworks has been established by the isolation of two related structures (I and II) from the same SBU units but different organic amines. Some of the present structures have close resemblance to the gallium phosphate phases known earlier. The compounds have been characterized by CHN analysis, powder XRD, IR, and TGA. (C) 2011 Elsevier B. V. All rights reserved.

Photolysis of arene chromium tricarbonyl complexes in presence of amine-boranes: Observation of sigma-borane complexes in solution

Activation of the B-H sigma-bond of amine-boranes on the chromium(0) center of arene chromium tricarbonyl complexes (eta(6)-arene) Cr(CO)(3) (arene = fluorobenzene, 1a; benzene, 1b and mesitylene, 1c) has been studied. Photolysis of 1b in presence of ammonia-borane (H3N center dot BH3, AB) and tert-butylamine-borane ((BuH2N)-Bu-t center dot BH3, TBAB) resulted in H-2 evolution and precipitation of a BNHx polymer. On the other hand, photolysis in the presence of trimethylamine-borane (Me3N center dot BH3, TMAB) resulted in the formation of a sigma-borane complex (2) along with Cr(CO)(5)(eta(1)-HBH2 center dot NMe3) (3). The sigma-borane complexes (eta(6)-arene) Cr-( CO)(2)(eta(1)-HBH2 center dot NMe3) (arene = fluorobenzene, 2a; benzene, 2b and mesitylene, 2c) were characterized in solution by H-1, B-11, and C-13 NMR spectroscopy. Electron withdrawing substituents on the arene ring provide the more stable sigma-borane moiety in this series of complexes. (C) 2011 Elsevier B.V. All rights reserved.

Chelating and bridging bis(diphenylphosphino)aniline complexes of copper(I)

The ligand bis(diphenylphosphino)aniline (dppan) has been shown to be a versatile ligand sporting different coordination modes and geometries as dictated by copper(I) and the counter ion. The molecular structures of its Cu(I) complexes were characterized by X-ray crystallography. The ligand was found in a chelating mode and monomeric complexes were formed when the ligand to copper ratio was 2: 1 and the anion was non-coordinating. However, with thiocyanate as the counter anion, the ligand was found to adopt two different modes, with one ligand chelating and the other acting as a monodentate ligand. With CuX (X = Cl, Br), dppan formed a tetrameric complex when the ligand and metal were reacted in the ratio of 1:1. But reactions containing ligand and metal in the ratios of 1: 2 or 2: 1, resulted in the formation of a mixture of species in solution. Crystallization however, led to the isolation of the tetrameric complex. Variable temperature P-31{H-1} NMR spectra of the isolated tetramers did not show the presence of chelated structures in solution. Tetra-alkylammonium salts were added to solutions of various complexes of dppan and studied by P-31{H-1} NMR to probe the effect of anions on the stability of complexes in solution. The Cu-dppan complexes were robust and did not interconvert with other structures in solution unlike the bis(diphenylphosphino) isopropylamine complexes. (C) 2011 Elsevier B.V. All rights reserved.

Coordination driven self-assembly of metallamacrocycles using ambidentate linkers and self-selection of single linkage isomer

Nicotinate-N-oxide and isonicotinate-N-oxide have been employed to synthesize four heterometallic metallamacrocycles (dppf)(2)Pd-2(nicotinate-N-oxide)(2)](OTf)(2) (1), (dppf)(2)Pt-2(nicotinate-N-oxide)(2)](OTf)(2) (2), (dppf) 2Pd2(isonicotinate-N-oxide)(2)](OTf)(2) (3) and (dppf)(2)Pt-2(isonicotinate-N-oxide)(2)](OTf)(2) (4). The complexes represent the first examples of metallamacrocycles driven by solely Pd(II)/Pt(II)-O coordination using carboxylate-N-oxide donor. All the complexes 1-4 are characterized by IR, UV-Vis, multinuclear NMR spectroscopic and ESI-MS studies. The molecular structures of the complexes 1 and 3 are unambiguously determined by single crystal X-ray diffraction analysis. Despite the possibility of formation of several linkage isomers due to ambidentate nature of the donors, exclusive formation of 2 + 2] self-assembled single isomeric metallamacrocycle in each case is interesting observation. (C) 2011 Elsevier B.V. All rights reserved.

Metallo-beta-lactamase and phosphotriesterase activities of some zinc(II) complexes

Metallo-beta-lactamases (m beta l) and phosphotriesterase (PTE) are zinc(II) enzymes, which hydrolyze the beta-lactam antibiotics and toxic organophosphotriesters, respectively. In the present work, we have synthesized a few asymmetric phenolate-based ligands by sequential Mannich reaction and their corresponding zinc(II) complexes. These zinc(II) complexes were studied for their m beta l and PTE activities. It is shown that the zinc(II) complexes can hydrolyze oxacillin, the beta-lactam antibiotic, at much higher rates as compared to the hydrolysis of p-nitrophenyl diphenylphosphate (PNPDPP), the phosphotriester. Among the complexes studied, the binuclear asymmetric complex 1 having a water molecule coordinated to one of the zinc(II) ions exhibits much better mbl activity than the mononuclear complexes. However, the mononuclear zinc(II) complexes having labile chloride ions exhibit significant PTE activity, which can be ascribed to the replacement of chloride ions by hydroxide ions during hydrolysis reactions. (C) 2011 Elsevier B.V. All rights reserved.

Dicopper(II) complexes showing DNA hydrolase activity and monomeric adduct formation with bis(4-nitrophenyl)phosphate

Ferromagnetic dicopper(II) complexes [Cu(2)(mu-O(2)CCH(3))(mu-OH)(L)(2)(mu-L(1))](PF(6))(2), where L = 1,10-phenanthroline (phen), L(1) = H(2)O in 1 and L = dipyrido[3,2-d:2',3'-f]quinoxaline (dpq), L(1) = CH(3)CN in 2, are prepared and structurally characterized. Crystals of 1 and 2 belong to the monoclinic space group of P2(1)/n and P2(1)/m, respectively. The copper(II) centers display distorted square-pyramidal geometry having a phenanthroline base and two oxygen atoms of the bridging hydroxo and acetate group in the basal plane. The fifth coordination site has weak axially bound bridging solvent molecule H(2)O in 1 and CH(3)CN in 2. The Cu center dot center dot center dot Cu distances are 3.034 and 3.046 angstrom in 1 and 2, respectively. The complexes show efficient hydrolytic cleavage of supercoiled pUC19 DNA as evidenced from the mechanistic studies that include T4 DNA ligase experiments. The binuclear complexes form monomeric copper(II) adducts [Cu(L)(2)(BNPP)](PF(6)) (L = phen, 3; dpq, 4) with bis(4-nitrophenyl)phosphate (BNPP) as a model phosphodiester. The crystal structures of 3 and 4 reveal distorted trigonal bipyramidal geometry in which BNPP binds through the oxygen atom of the phosphate. The kinetic data of the DNA cleavage reactions of the binuclear complexes under pseudo- and true-Michaelis-Menten conditions indicate remarkable enhancement in the DNA hydrolysis rate in comparison to the control data. (C) 2011 Elsevier B.V. All rights reserved.

Synthesis, spectroscopic properties and biological evaluation of transition metal complexes of salicylhydrazone of anthranilhydrazide: X-ray crystal structure of copper complex

The transition metal complexes of salicylhydrazone of anthranilhydrazide (H2L) were synthesised. The structures of metal complexes were characterized by various spectroscopic [IR, NMR, UV-Vis, EPR], thermal and other physicochemical methods. The single-crystal X-ray diffraction study of [Cu(HL)Cl]center dot H2O reveal its orthorhombic system with space group P2(1)2(1)2 and Z=4. The copper center has a distorted square planar geometry with ONO and Cl as the donor atoms. The ligand and its metal chelates have been screened for their antimicrobial and anti-tubercular activities using serial dilution method. Metal complexes in general have exhibited better antibacterial and antifungal activity than the free ligand and in few cases better than the standard used. Among the bacterial strains used, the complexes are highly potent against Gram-positive strains compared to Gram-negative. Anti-tubercular activity exhibited by the Co(II) complex is comparable with the standard used. (C) 2011 Elsevier B. V. All rights reserved.

Loading of single-walled carbon nanotubes in cationic cholesterol suspensions significantly improves gene transfection efficiency in serum

We present here a series of cholesterol based cationic lipid suspensions that solubilize single-walled carbon nanotubes (SWCNT) efficiently in water. Each cationic lipid formulation was characterized in terms of their energy minimized molecular structures, bilayer widths of the aggregates based on X-ray diffraction. Then these aggregates were investigated pertaining to their DNA binding and release efficiency, effect of CNT inclusion on the stability of cationic cholesterol lipid-DNA complexes, Zeta potential values and changes in the chiro-optical property of DNA, effect on Raman spectral shift and changes in morphology by SEM and AFM. Each cationic lipid formulation was optimized for the amount of SWCNT solubilized in water, lipid-DNA ratio, amount of the plasmid DNA that can be transfected and the effect on the cellular toxicity. The resulting SWCNT-lipid formulations were then used for in vitro transfection of pEGFP-C3 in A549 (human alveolar basal epithelial) cells and HeLa (human cervical cancer) cells. Advantageously, the CNT-loaded formulations confer an excellent transfection efficiency even in high percentages of blood serum and showed significantly better gene transfer efficiency compared to one of the potent, well-known commercial transfection reagent, Lipofectamine2000.

Ferrocene-Conjugated Copper(II) Complexes of L-Methionine and Phenanthroline Bases: Synthesis, Structure, and Photocytotoxic Activity

Ferrocene-conjugated reduced Schiff base (Fc-metH) copper(II) complexes of L-methionine and phenanthroline bases, namely, Cu(Fc-met)(B)](NO3), where B is 1,10-phenanthroline (phen in 1), dipyrido3,2-d:2',3'-f]quinoxaline (dpq in 2), dipyrido3,2-a:2',3'-c]phenazine (dppz in 3), and 2-(naphthalen-1-yl)-1H-imidazo4,5-f]1,10]phenanthroline (nip in 4), were prepared and characterized and their photocytotoxicity studied (Fc = ferrocenyl moiety). Complexes Cu(Ph-met)(B)](NO3) of the reduced Schiff base from benzaldehyde and L-methionine (Ph-metH) and B (phen in 5, dppz in 6) were prepared and used as control species. Complexes 1 and 5 were structurally characterized by X-ray crystallography. Complex 1 as a discrete monomer has a CuN3OS core with the thiomethyl group as the axial ligand. Complex 5 has a polymeric structure with a CuN3O2 core in the solid state. Complexes 5 and 6 are formulated as Cu(Ph-met)(B)(H2O)] (NO3) in an aqueous phase based on the mass spectral data. Complexes 1-4 showed the Cu(II)-Cu(I) and Fc(+)-Fc redox couples at similar to 0.0 and similar to 0.5 V vs SCE, respectively, in DMF-0.1 M (Bu4N)-N-n](ClO4). A Cu(II)-based weak d-d band near 600 nm and a relatively strong ferrocenyl band at similar to 450 nm were observed in DMF-Tris-HCl buffer (1:4 v/v). The complexes bind to calf thymus DNA, exhibit moderate chemical nuclease activity forming (OH)-O-center dot radical species, and are efficient photocleavers of pUC19 DNA in visible light of 454, 568, and 647 rim, forming (OH)-O-center dot radical as the reactive oxygen species. They are cytotoxic in HeLa (human cervical cancer) and MCF-7 (human breast cancer) cells, showing an enhancement of cytotoxicity upon visible light irradiation. Significant change in the nuclear morphology of the HeLa cells was observed with 3 in visible light compared to the nonirradiated sample. Confocal imaging using 4 showed its nuclear localization within the HeLa cells.

Ag@AgI, Core@Shell Structure in Agarose Matrix as Hybrid: Synthesis, Characterization, and Antimicrobial Activity

A novel in situ core@shell structure consisting of nanoparticles of Ag (Ag Nps) and AgI in agarose matrix (Ag@ AgI/agarose) has been synthesized as a hybrid, in order to have an efficient antibacterial agent for repetitive usage with no toxicity. The synthesized core@shell structure is very well characterized by XRD, UV-visible, photoluminescence, and TEM. A detailed antibacterial studies including repetitive cycles are carried out on Gram-negative Escherichia coli (E. coli) and Gram-positive Staphylococcus aureus (S. aureus) bacteria in saline water, both in dark and on exposure to visible light. The hybrid could be recycled for the antibacterial activity and is nontoxic toward human cervical cancer cells (HeLa cells). The water insoluble Ag@AgI in agarose matrix forms a good coating on quartz, having good mechanical strength. EPR and TEM studies are carried out on the Ag@AgI/agarose and the bacteria, respectively, to elucidate a possible mechanism for killing of the bacteria.

Synthesis and spectral characterization of cyclotriphosphazene based 18-membered macrocycles

New 18-membered cyclotriphosphazene-containing macrocycles 7-10 were obtained by 1 + 1 condensation reaction of dispiro-N3P3(C12H8O2)(2)((N(Me)N=CH)(2) N4C20H26)] (2) with N,N'-dimethyl-ethylenediamine-1,4-diyldimethylenebis(4-methyl-2-formylph enol) (3), N,N'-dimethyl-ethylenediamine-1,4-diyldimethylenebis(4,5-dimethyl-2-form ylphenol) (4), N,N'-dimethyl-ethylenediamine-1,4-diyldimethylenebis(5-chloro-2-formylph enol) (5) and N,N'-dimethyl-ethylenediamine-1,4-diyldimethylenebis(5-bromo-2-formylphe nol) (6), respectively. (C) 2012 Elsevier B.V. All rights reserved.

An Antitubulin Agent BCFMT Inhibits Proliferation of Cancer Cells and Induces Cell Death by Inhibiting Microtubule Dynamics

Using cell based screening assay, we identified a novel anti-tubulin agent (Z)-5-((5-(4-bromo-3-chlorophenyl)furan-2-yl)methylene)-2-thioxothiazoli din-4-one (BCFMT) that inhibited proliferation of human cervical carcinoma (HeLa) (IC50, 7.2 +/- 1.8 mu M), human breast adenocarcinoma (MCF-7) (IC50, 10.0 +/- 0.5 mu M), highly metastatic breast adenocarcinoma (MDA-MB-231) (IC50, 6.0 +/- 1 mu M), cisplatin-resistant human ovarian carcinoma (A2780-cis) (IC50, 5.8 +/- 0.3 mu M) and multi-drug resistant mouse mammary tumor (EMT6/AR1) (IC50, 6.5 +/- 1 mu M) cells. Using several complimentary strategies, BCFMT was found to inhibit cancer cell proliferation at G2/M phase of the cell cycle apparently by targeting microtubules. In addition, BCFMT strongly suppressed the dynamics of individual microtubules in live MCF-7 cells. At its half maximal proliferation inhibitory concentration (10 mu M), BCFMT reduced the rates of growing and shortening phases of microtubules in MCF-7 cells by 37 and 40%, respectively. Further, it increased the time microtubules spent in the pause (neither growing nor shortening detectably) state by 135% and reduced the dynamicity (dimer exchange per unit time) of microtubules by 70%. In vitro, BCFMT bound to tubulin with a dissociation constant of 8.3 +/- 1.8 mu M, inhibited tubulin assembly and suppressed GTPase activity of microtubules. BCFMT competitively inhibited the binding of BODIPY FL-vinblastine to tubulin with an inhibitory concentration (K-i) of 5.2 +/- 1.5 mu M suggesting that it binds to tubulin at the vinblastine site. In cultured cells, BCFMT-treatment depolymerized interphase microtubules, perturbed the spindle organization and accumulated checkpoint proteins (BubR1 and Mad2) at the kinetochores. BCFMT-treated MCF-7 cells showed enhanced nuclear accumulation of p53 and its downstream p21, which consequently activated apoptosis in these cells. The results suggested that BCFMT inhibits proliferation of several types of cancer cells including drug resistance cells by suppressing microtubule dynamics and indicated that the compound may have chemotherapeutic potential.

Novel tetranuclear distorted open-cubane copper complex containing oximate bridges: Synthesis, crystal structure, DNA binding and cleavage activity

The synthesis, molecular structure, DNA binding and nuclease activity of Cu4O4 open-cubane tetranuclear copper(II) complex with 3-2-(ethyl amino)ethyl]imino]-2-butanoneoxime (HL) are reported for the first time. The neutral tetranuclear Cu4L4(ClO4)(4)] complex crystallizes in tetragonal space group P (4) over bar2(1)c with the unit cell parameters; a = 13.798(4) angstrom, b = 13.798(4) angstrom, c = 14.119(6) angstrom, V = 2688(16) angstrom(3), Z = 8, R = 0.0636. Symmetrically equivalent copper atoms exhibit a CuN3O3 elongated distorted octahedral coordination environment, with three nitrogen atoms of the L ligand and one oxime-oxygen atom of second L ligand at equatorial positions, one oxime-oxygen atom of the third L ligand and perchlorate oxygen at axial positions. The complex shows quasireversible cyclic voltammetric response at 0.805 V (Delta E-p = 277 mV) at 100 mV s (1) in DMF for the Cu(II)/Cu(I) redox couple. The binding study of the complex with calf-thymus DNA has been investigated using absorption spectrophotometry. The complex shows strong nuclease activity on stranded pBR 322 plasmid DNA in the presence of hydrogen peroxide and marginal nuclease activity in the presence of reducing agent (dithiothreitol). (C) 2012 Elsevier B. V. All rights reserved.

Naphthylhydrazone based selective and sensitive chemosensors for Cu2+ and their application in bioimaging

Two new hydroxynaphthyl-hydrazone based fluorogenic chemosensors R-1 and R-2 have been synthesized by Schiff base condensation of Tris(4-formylphenyl)amine with 1-hydroxynaphthalene-2-hydrazide and 1-hydroxynaphthalene-2-carbohydrazone, respectively. They are examined as highly selective and sensitive receptors for Cu2+ ions in aqueous medium. Electronic absorption as well as fluorescence titration studies of receptors R-1 and R-2 with different metal cations in H2O/CH3CN medium showed highly selective and very rapid (< 2 min) binding affinity towards Cu2+ ions even in the presence of other commonly coexisting metal ions such as Na+, K+, Mg2+, Ca2+, Mn2+, Fe2+, Co2+, Ni2+, Zn2+, Cd2+ and Hg2+. Quantification of the fluorescence titration analysis indicated that these newly synthesized receptors (R-1 and R-2) can indicate the presence of Cu2+ ions even at very low concentrations of 598 and 676 ppt, respectively. In addition, the propensity of these receptors as bio-imaging fluorescent probes to detect Cu2+ ions in human cervical HeLa cancer cell lines and their cytotoxicity against HeLa cells have been investigated.

Cellular uptake and remarkable photocytotoxicity of pyrenylter pyridine oxovanadium(IV) complexes of dipyridophenazine bases

Pyrenylterpyridine (pytpy) oxovanadium(IV) complexes VO(pytpy)(L)]Cl-2 (1-6) of the dipyridophenazine bases (L), viz., dipyrido-6,7,8,9-tetrahydrophenazine (dpqC in 1), dipyrido3,2-a:2',3'-c]phenazine-2-carboxylic acid (dppzc in 2), dipyrido3,2-a:2',3'-c]phenazine-11-sulfonic acid (dppzs in 3), 7-aminodipyrido3,2-a:2',3'-c]phenazine (dppza in 4), benzo-i]dipyrido3,2-a:2',3'-c]phenazine (dppn in 5) and dipyrido3,2-a:2',3'-c]phenazine (dppz in 6) were prepared, characterized and their DNA binding, photocleavage activity and photocytotoxicity studied. The complexes which showed a d-d band near 750 nm in DMF are efficient binders to calf thymus DNA (K-b: 3.2 x 10(5)-2.9 x 10(6) M-1). The complexes showed significant pUC19 DNA cleavage in near-IR light of 785 nm forming center dot OH radicals and photocytotoxicity in HeLa cells in visible light with the benzo-i] dipyrido3,2-a:2',3'-c]phenazine complex 5 showing a remarkably low IC50 value of 0.036 mu M. Flow-cytometric analysis shows a high sub-G1 phase cell cycle arrest in HeLa cells by the complexes on photo-irradiation. The photocytotoxicity correlates well with the hydrophobicity, photosensitizing ability and DNA binding propensity of the complexes. (C) 2012 Elsevier B.V. All rights reserved.