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1.  μ-Oxalato-bis­[(2,2′-bipyridyl)­copper(II)] bis(perchlorate) dimethyl­formamide disolvate monohydrate 
The title compound, [Cu2(C2O4)(C10H8N2)4](ClO4)2·2C3H7NO·H2O, contains doubly charged centrosymmetric dinuclear oxalato-bridged copper(II) complex cations, perchlorate anions, and DMF and water solvate mol­ecules. In the complex cation, the oxalate ligand is coordinated in a bis-bidentate bridging mode to the Cu atoms. Each Cu atom has a distorted tetra­gonal-bipyramidal environment, being coordinated by two N atoms of the two chelating bipy ligands and two O atoms of the doubly deprotonated oxalate anion. Pairs of perchlorate anions and water mol­ecules are linked into recta­ngles by O—H⋯O bonds in which the perchlorate O atoms act as acceptors and the water mol­ecules as donors. Methyl groups of the DMF solvent molecule are disordered over two sites with occupancies of 0.453 (7):0.547 (7), and the water molecule is half-occupied.
PMCID: PMC3008067  PMID: 21588513
Toxicology and applied pharmacology  2006;215(2):158-167.
Cutaneous drug reactions (CDRs) associated with sulfonamides are believed to be mediated through the formation of reactive metabolites that result in cellular toxicity and protein haptenation. We evaluated the bioactivation and toxicity of sulfamethoxazole (SMX) and dapsone (DDS) in normal human dermal fibroblasts (NHDF). Incubation of cells with DDS or its metabolite (D-NOH) resulted in protein haptenation readily detected by confocal microscopy and ELISA. While the metabolite of SMX (S-NOH) haptenated intracellular proteins, adducts were not evident in incubations with SMX. Cells expressed abundant N-acetyltransferase-1 (NAT1) mRNA and activity, but little NAT2 mRNA or activity. Neither NAT1 nor NAT2 protein were detectable. Incubation of NHDF with S-NOH or D-NOH increased reactive oxygen species formation and reduced glutathione content. NHDF were less susceptible to the cytotoxic effect of S-NOH and D-NOH than are keratinocytes. Our studies provide the novel observation that NHDF are able to acetylate both arylamine compounds and bioactivate the sulfone, DDS, giving rise to haptenated proteins. The reactive metabolites of SMX and DDS also provoke oxidative stress in these cells in a time- and concentration-dependent fashion. Further work is needed to determine the role of the observed toxicity in mediating CDRs observed with these agents.
PMCID: PMC1615915  PMID: 16603214
sulfonamides; cutaneous drug reactions; fibroblasts; protein haptenation; toxicity; N-acetyltransferase
3.  Bis[μ-N′-(adamantan-1-ylcarbon­yl)-2-oxidobenzohydrazidato(3−)]tetra­pyridine­trinickel(II) dimethyl­formamide monosolvate monohydrate 
In the title trinuclear NiII compound, [Ni3(C18H19N2O3)2(C5H5N)4]·C3H7NO·H2O, three NiII cations are bridged by two N′-(adamantan-1-ylcarbon­yl)-2-oxidobenzohydrazidate trianions. The central NiII cation has a distorted octa­hedral N4O2 coordination environment where a reverse torsion occurs between the two bridging ligands, whereas the two NiII cations on the sides each adopt an N2O2 square-planar coordination. Weak intra­molecular C—H⋯O and C—H⋯N inter­actions help to stabilize the mol­ecular structure. In the crystal, the lattice water mol­ecule links with the NiII complex and dimethyl­formamide solvent mol­ecule via O—H⋯O hydrogen bonding.
PMCID: PMC3344353  PMID: 22590119
Inorganic chemistry  2007;46(22):9192-9200.
The occurence of a heteroatom X (C, N, or O) in the MoFe7S9X core of the iron-molybdenum cofactor of nitrogenase has encouraged synthetic attempts to prepare high nuclearity M-Fe-S-X clusters containing such atoms. We have previously shown that reaction of the edge-bridged double cubane [(Tp)2Mo2Fe6S8(PEt3)4] (1) with nucleophiles HQ− affords the clusters [(Tp)2Mo2Fe6S8Q(QH)2]3− (Q = S, Se) in which HQ− is a terminal ligand and Q2− is a μ2-bridging atom in the core. Reactions with OH- used as such or oxygen nucleophiles generated in acetonitrile from (Bu3Sn)2O or Me3SnOH and fluoride were examined. Reaction of 1 with Et4NOH in acetonitrile/water generates [(Tp)2Mo2Fe6S9(OH)2]3− (3), isolated as [(Tp)2Mo2Fe6S9(OH)(OC(=NH)Me)(H2O)]3− and shown to have the [Mo2Fe6(μ2-S)2(μ3-S)6(μ6-S)] core topology very similar to the PN cluster of nitrogenase. The reaction system 1/Et4NOH in acetonitrile/methanol yields the PN-type cluster [(Tp)2Mo2Fe6S9(OMe)2(H2O)]3− (5). The system 1/Me3SnOH/F− affords the oxo-bridged double PN-type cluster {[(Tp)2Mo2Fe6S9(μ2-O)]2}5− (7), convertible to the oxidized cluster {[(Tp)2Mo2Fe6S9(μ2-O)]2}4− (6), which is prepared independently from [(Tp)2Mo2Fe6S9F2(H2O)]3−/(Bu3Sn)2O. In the preparations of 3–5 and 7, hydroxide liberates sulfide from 1 leading to the formation of PN-type clusters. Unlike reactions with HQ−, no oxygen atoms are integrated into the core structures of the products. However, the half-dimer composition [Mo2Fe6S9O] relates to the MoFe7S9 consitution of the putative native cluster with X = O. (Tp = hydrotris(pyrazolyl) borate(1-)).
PMCID: PMC2527064  PMID: 17892284
5.  Lignin-Derived Compounds as Efficient Laccase Mediators for Decolorization of Different Types of Recalcitrant Dyes 
Ten phenols were selected as natural laccase mediators after screening 44 different compounds with a recalcitrant dye (Reactive Black 5) as a substrate. Their performances were evaluated at different mediator/dye ratios and incubation times (up to 6 h) by the use of Pycnoporus cinnabarinus and Trametes villosa laccases and were compared with those of eight known synthetic mediators (including -NOH- compounds). Among the six types of dyes assayed, only Reactive Blue 38 (phthalocyanine) was resistant to laccase-mediator treatment under the conditions used. Acid Blue 74 (indigoid dye), Reactive Blue 19 (anthraquinoid dye), and Aniline Blue (triarylmethane-type dye) were partially decolorized by the laccases alone, although decolorization was much more efficient and rapid with mediators, whereas Reactive Black 5 (diazo dye) and Azure B (heterocyclic dye) could be decolorized only in the presence of mediators. The efficiency of each natural mediator depended on the type of dye to be treated but, with the only exception being Azure B (<50% decolorization), nearly complete decolorization (80 to 100%) was attained in all cases. Similar rates were attained with the best synthetic mediators, but the reactions were significantly slower. Phenolic aldehydes, ketones, acids, and esters related to the three lignin units were among the best mediators, including p-coumaric acid, vanillin, acetovanillone, methyl vanillate, and above all, syringaldehyde and acetosyringone. The last two compounds are especially promising as ecofriendly (and potentially cheap) mediators for industrial applications since they provided the highest decolorization rates in only 5 to 30 min, depending on the type of dye to be treated.
PMCID: PMC1082544  PMID: 15812000
6.  catena-Poly[[[aqua­chlorido­manganese(II)]-bis­[μ-1,1′-(oxydi-p-phenyl­ene)di-1H-imidazole-κ2 N 3:N 3′]] chloride dimethyl­formamide mono­solvate monohydrate] 
The title coordination polymer, {[MnCl(C18H14N4O)2(H2O)]Cl·C3H7NO·H2O}n, obtained by the solvothermal reaction of BIDPE and manganese(II) salt in H2O/DMF (DMF is dimethyl­formamide), is composed of a chain of [Mn2(BIDPE)2] [BIDPE is 1,1′-(oxydi-p-phenyl­ene)di-1H-imidazole] metallocyclic rings that exhibit inversion symmetry. The coordination about the Mn(II) ions is distorted octahedral with a MnClN4O coordination set. In the crystal, the polymeric chains are linked by O—H⋯Cl hydrogen bonds, forming a two-dimensional network parallel to (100). A number of C—H⋯Cl and C—H⋯O inter­actions are also present.
PMCID: PMC3051568  PMID: 21522845
7.  Safe and targeted anticancer therapy for ovarian cancer using a novel class of curcumin analogs 
A diagnosis of advanced ovarian cancer is the beginning of a long and arduous journey for a patient. Worldwide, approximately half of the individuals undergoing therapy for advanced cancer will succumb to the disease, or consequences of treatment. Well-known and widely-used chemotherapeutic agents such as cisplatin, paclitaxel, 5-fluorouracil, and doxorubicin are toxic to both cancer and non-cancerous cells, and have debilitating side effects Therefore, development of new targeted anticancer therapies that can selectively kill cancer cells while sparing the surrounding healthy tissues is essential to develop more effective therapies. We have developed a new class of synthetic curcumin analogs, diarylidenyl-piperidones (DAPs), which have higher anticancer activity and enhanced bio-absorption than curcumin. The DAP backbone structure exhibits cytotoxic (anticancer) activity, whereas the N-hydroxypyrroline (-NOH) moiety found on some variants functions as a cellular- or tissue-specific modulator (antioxidant) of cytotoxicity. The anticancer activity of the DAPs has been evaluated using a number of ovarian cancer cell lines, and the safety has been evaluated in a number of non-cancerous cell lines. Both variations of the DAP compounds showed similar levels of cell death in ovarian cancer cells, however the compounds with the -NOH modification were less toxic to non-cancerous cells. The selective cytotoxicity of the DAP–NOH compounds suggests that they will be useful as safe and effective anticancer agents. This article reviews some of the key findings of our work with the DAP compounds, and compares this to some of the targeted therapies currently used in ovarian cancer therapy.
PMCID: PMC3665575  PMID: 23663277
Ovarian cancer; Targeted therapy; STAT3; Curcumin analog; Curcumin
8.  Tris(1,10-phenanthroline-κ2 N,N′)nickel(II) hexa­oxido-μ-peroxido-disulfate­(VI) N,N-dimethyl­formamide disolvate monohydrate 
The asymmetric unit of the title complex, [Ni(C12H8N2)3]S2O8·2C3H7NO·H2O, consists of a complex [Ni(phen)3]2+ cation and one isolated pds anion, with two DMF mol­ecules and one water mol­ecule as solvates (where phen is 1,10-phenanthroline, pds is the hexa­oxido-μ-peroxoido-di­sulf­ate dianion and DMF is dimethyl­formamide). The [Ni(phen)3]2+ cation is regular, with an almost ideal NiII bond-valence sum of 2.07 v.u. The group, as well as the water solvent mol­ecule, are well behaved in terms of crystallographic order, but the remaining three mol­ecules in the structure display different kinds of disorder, viz. the two DMF mol­ecules mimic a twofold splitting and the pds anion has both S atoms clamped at well-determined positions but with a not-too-well-defined central part. These peculiar behaviours are a consequence of the hydrogen-bonding inter­actions: the outermost SO3 parts of the pds anion are heavily connected to the complex cations via C—H⋯O hydrogen bonding, generating an [Ni(phen)3]pds network and providing for the stability of the terminal pds sites. Also, the water solvent mol­ecule is strongly bound to the structure (being a donor of two strong bonds and an acceptor of one) and is accordingly perfectly ordered. The peroxide O atoms in the pds middle region, instead, appear as much less restrained into their sites, which may explain their tendency to disorder. The cation–anion network leaves large embedded holes, amounting to about 28% of the total crystal volume, which are occupied by the DMF mol­ecules. The latter are weakly inter­acting with the rest of the structure, which renders them much more labile and, accordingly, prone to disorder.
PMCID: PMC3588241  PMID: 23476355
9.  Bis[N′-(2-oxo-1H-indol-3-ylidene)furan-2-carbohydrazidato-κ3 O,N′,O′]manganese(II) N,N-dimethyl­formide monosolvate monohydrate 
In the title compound, [Mn(C13H8N3O3)2]·C3H7NO·H2O, the metal atom is O,N,O′-chelated by two deprotonated Schiff bases and exists in a distorted octa­hedral geometry. The N–H groups, the carbonyl group of the DMF mol­ecule and the uncoord­inated water mol­ecule engage in N—H⋯O and O—H⋯O hydrogen-bonding inter­actions, generating a hydrogen-bonded ribbon that propagates along [110].
PMCID: PMC3009305  PMID: 21588862
10.  Bis[N′-(2-oxo-1H-indol-3-ylidene)thiophene-2-carbohydrazidato-κ3 O,N′,O′]zinc(II) N,N-dimethyl­formide mono­solvate monohydrate 
The metal atom of the title compound, [Zn(C13H8N3O2S)2]·C3H7NO·H2O, is O,N,O′-chelated by two deprotonated Schiff bases and it exists in a distorted octa­hedral geometry. The N–H groups of the ligands, the carbonyl group of the DMF mol­ecule and uncoordinated water mol­ecule engage in N—H⋯O and O—H⋯O inter­actions, generating a hydrogen-bonded ribbon that propagates along [110]. One thienyl ring is disordered over two positions in a 1:1 ratio.
PMCID: PMC3009315  PMID: 21588861
11.  Preparation of aluminum(III) (bis(amido)pyridine)(thiolate) complexes: unexpected transmetalation mediated by LiAlH4 
Inorganica chimica acta  2012;382:19-26.
Treatment of an unsymmetrical bis(imino)pyridyl-thiolate zinc(II) complex [ZnII(LN3S)(OTf)] (1) with LiAlH4 results in the double reduction of the two imino groups in the ligand backbone, and at the same time causes a rare transmetalation reaction to occur. The products formed in this reaction are two novel aluminium(III) bis(amido)pyridyl-thiolate complexes [(R,S/S,R-[AlIII(LH2N3S)(THF)] (2a) and [(R,R/S,S-[AlIII(LH2N3S)(THF)] (2b), which are diastereomers of each other. These complexes have been characterized by single-crystal X-ray diffraction and 1H NMR spectroscopy. Single crystal X-ray structure analysis shows that the AlIII ion is bound in an almost idealized square pyramidal geometry in 2a, while being held in a more distorted square pyramidal geometry in 2b. The major difference between 2a and 2b arises in the orientation of the terminal methyl groups of the ligand backbone in relation to the AlIIIN3S plane. These two complexes are crystallized at different temperatures (room temperature vs −35 °C), allowing for their separate isolation. Structural analysis shows that these complexes are reduced by the formal addition of one hydride ion to each imino group, resulting in a deprotonated bis(amido)pyridyl-thiolate ligand. A detailed analysis of metrical parameters rules out the possibility of pure one- or two-electron reduction of the π-conjugated bis(imino)pyridine framework. 1H NMR spectra reveal a rich pattern in solution indicating that the solution state structures for 2a and 2b match those observed in the solid-state crystal structures, and reveal that both complexes are severely conformationally restricted. Direct organic synthetic methods failed to produce the reduced bis(amino)pyridyl-thiol ligand in pure form, but during the course of these efforts an unusual unsymmetrical aminopyridyl ketone, 1-(6-(1-(2,6-diisopropylphenylamino)ethyl)pyridin-2-yl)ethanone was synthesized in good yield and can be used as a possible precursor for further ligand development.
PMCID: PMC3278085  PMID: 22345823
aluminum; bis(imino)pyridine; transmetalation; zinc; ligand reduction; ligand design
12.  A Novel Helicase-Type Protein in the Nucleolus: Protein NOH61 
Molecular Biology of the Cell  2000;11(4):1153-1167.
We report the identification, cDNA cloning, and molecular characterization of a novel, constitutive nucleolar protein. The cDNA-deduced amino acid sequence of the human protein defines a polypeptide of a calculated mass of 61.5 kDa and an isoelectric point of 9.9. Inspection of the primary sequence disclosed that the protein is a member of the family of “DEAD-box” proteins, representing a subgroup of putative ATP-dependent RNA helicases. ATPase activity of the recombinant protein is evident and stimulated by a variety of polynucleotides tested. Immunolocalization studies revealed that protein NOH61 (nucleolar helicase of 61 kDa) is highly conserved during evolution and shows a strong accumulation in nucleoli. Biochemical experiments have shown that protein NOH61 synthesized in vitro sediments with ∼11.5 S, i.e., apparently as homo-oligomeric structures. By contrast, sucrose gradient centrifugation analysis of cellular extracts obtained with buffers of elevated ionic strength (600 mM NaCl) revealed that the solubilized native protein sediments with ∼4 S, suggestive of the monomeric form. Interestingly, protein NOH61 has also been identified as a specific constituent of free nucleoplasmic 65S preribosomal particles but is absent from cytoplasmic ribosomes. Treatment of cultured cells with 1) the transcription inhibitor actinomycin D and 2) RNase A results in a complete dissociation of NOH61 from nucleolar structures. The specific intracellular localization and its striking sequence homology to other known RNA helicases lead to the hypothesis that protein NOH61 might be involved in ribosome synthesis, most likely during the assembly process of the large (60S) ribosomal subunit.
PMCID: PMC14838  PMID: 10749921
13.  Synthesis, Characterization, and Interaction with Biomolecules of Platinum(II) Complexes with Shikimic Acid-Based Ligands 
Starting from the active ingredient shikimic acid (SA) of traditional Chinese medicine and NH2(CH2)nOH, (n = 2–6), we have synthesized a series of new water-soluble Pt(II) complexes PtLa–eCl2, where La–e are chelating diamine ligands with carbon chain covalently attached to SA (La–e = SA-NH(CH2)nNHCH2CH2NH2; La, n = 2; Lb, n = 3; Lc, n = 4; Ld, n = 5; Le, n = 6). The results of the elemental analysis, LC-MS, capillary electrophoresis, and 1H, 13C NMR indicated that there was only one product (isomer) formed under the present experimental conditions, in which the coordinate mode of PtLa–eCl2 was two-amine bidentate. Their in vitro cytotoxic activities were evaluated by MTT method, where these compounds only exhibited low cytotoxicity towards BEL7404, which should correlate their low lipophilicity. The interactions of the five Pt(II) complexes with DNA were investigated by agarose gel electrophoresis, which suggests that the Pt(II) complexes could induce DNA alteration. We also studied the interactions of the Pt(II) complexes with 5′-GMP with ESI-MS and 1H NMR and found that PtLbCl2, PtLcCl2, and PtLdCl2 could react with 5′-GMP to form mono-GMP and bis-GMP adducts. Furthermore, the cell-cycle analysis revealed that PtLbCl2, PtLcCl2 cause cell G2-phase arrest after incubation for 72 h. Overall, these water-soluble Pt(II) complexes interact with DNA mainly through covalent binding, which blocks the DNA synthesis and replication and thus induces cytotoxicity that weakens as the length of carbon chain increases.
PMCID: PMC3603162  PMID: 23533373
14.  Kidney dendritic cell activation is required for progression of renal disease in a mouse model of glomerular injury 
The Journal of Clinical Investigation  2009;119(5):1286-1297.
The progression of kidney disease to renal failure correlates with infiltration of mononuclear immune cells into the tubulointerstitium. These infiltrates contain macrophages, DCs, and T cells, but the role of each cell type in disease progression is unclear. To investigate the underlying immune mechanisms, we generated transgenic mice that selectively expressed the model antigens ovalbumin and hen egg lysozyme in glomerular podocytes (NOH mice). Coinjection of ovalbumin-specific transgenic CD8+ CTLs and CD4+ Th cells into NOH mice resulted in periglomerular mononuclear infiltrates and inflammation of parietal epithelial cells, similar to lesions frequently observed in human chronic glomerulonephritis. Repetitive T cell injections aggravated infiltration and caused progression to structural and functional kidney damage after 4 weeks. Mechanistic analysis revealed that DCs in renal lymph nodes constitutively cross-presented ovalbumin and activated CTLs. These CTLs released further ovalbumin for CTL activation in the lymph nodes and for simultaneous presentation to Th cells by distinct DC subsets residing in the kidney tubulointerstitium. Crosstalk between tubulointerstitial DCs and Th cells resulted in intrarenal cytokine and chemokine production and in recruitment of more CTLs, monocyte-derived DCs, and macrophages. The importance of DCs was established by the fact that DC depletion rapidly resolved established kidney immunopathology. These findings demonstrate that glomerular antigen–specific CTLs and Th cells can jointly induce renal immunopathology and identify kidney DCs as a mechanistic link between glomerular injury and the progression of kidney disease.
PMCID: PMC2673875  PMID: 19381017
15.  Synthesis, Crystal Structures, and DNA Binding Properties of Zinc(II) Complexes with 3-Pyridine Aldoxime 
The employment of 3-pyridine aldoxime, (3-py)CHNOH, in ZnII chemistry has afforded two novel compounds: [Zn(acac)2{(3-py)CHNOH}]·H2O (1·H2O) [where acac− is the pentane-2,4-dionato(-1) ion] and [Zn2(O2CMe)4{(3-py)CHNOH}2] (2). Complex 1·H2O crystallizes in the monoclinic space group P21/n. The ZnII ion is five-coordinated, surrounded by four oxygen atoms of two acac− moieties and by the pyridyl nitrogen atom of the (3-py)CHNOH ligand. Molecules of 1 interact with the water lattice molecules forming a 2D hydrogen-bonding network. Complex 2 crystallizes in the triclinic P-1 space group and displays a dinuclear paddle-wheel structure. Each ZnII exhibits a perfect square pyramidal geometry, with four carboxylate oxygen atoms at the basal plane and the pyridyl nitrogen of one monodentate (3-py)CHNOH ligand at the apex. DNA mobility shift assays were performed for the determination of the in vitro effect of both complexes on the integrity and the electrophoretic mobility of pDNA.
PMCID: PMC2971566  PMID: 21076521
16.  Safe and targeted anticancer efficacy of a novel class of antioxidant-conjugated difluoro-diarylidenylpiperidones: Differential cytotoxicity in healthy and cancer cells 
Free radical biology & medicine  2010;48(9):1228-1235.
The development of smart anti-cancer drugs that can selectively kill cancer cells while sparing the surrounding healthy tissues/cells unharmed is of paramount importance for safe and effective cancer therapy. We report a novel class of bifunctional compounds based on diarylidenylpiperidone (DAP) conjugated with an N-hydroxypyrroline (NOH, a nitroxide precursor) group. We hypothesized that the DAP would have cytotoxic (anti-cancer) activity, while the NOH moiety would function as a tissue-specific modulator (anti-oxidant) of cytotoxicity. The study used four DAPs, namely H-4073 and H-4318 without NOH and HO-3867 and HO-4200 with NOH substitution. The goal of the study was to evaluate the ‘proof-of-concept’ anticancer-versus-antioxidant efficacy of the DAPs using a number of cancerous (breast, colon, head and neck, liver, lung, ovarian, and prostate cancer) and noncancerous (smooth muscle, aortic endothelial, and ovarian surface epithelial cells) human cell lines. Cytotoxicity was determined using an MTT-based cell viability assay. All four compounds induced significant loss of cell viability in cancer cells, while HO-3867 and HO-4200 showed significantly less cytotoxicity in noncancerous cells. EPR measurements showed a metabolic conversion of the N-hydroxylamine function to nitroxide with significantly higher levels of the metabolite and superoxide radical-scavenging (antioxidant) activity in noncancerous cells when compared to cancer cells. Western-blot analysis showed that the DAP-induced growth arrest and apoptosis in cancer cells were mediated by inhibition of STAT3 phosphorylation at Tyr705 and Ser727 residues and induction of apoptotic markers of cleaved caspase-3 and PARP. The results suggest that the antioxidant-conjugated DAPs will be useful as a safe and effective anticancer agent for cancer therapy.
PMCID: PMC2847669  PMID: 20156552
human cancer cell line; ovarian cancer; diarylidenylpiperidone; STAT3; curcumin; nitroxide
17.  Toward Functional Carboxylate-Bridged Diiron Protein Mimics: Achieving Structural Stability and Conformational Flexibility Using a Macrocylic Ligand Framework 
Journal of the American Chemical Society  2011;133(27):10568-10581.
A dinucleating macrocycle, H2PIM, containing phenoxylimine metal-binding units has been prepared. Reaction of H2PIM with [Fe2(Mes)4] (Mes = 2,4,6-trimethylphenyl) and sterically hindered carboxylic acids, Ph3CCO2H or ArTolCO2H (2,6-bis(p-tolyl)benzoic acid), afforded complexes [Fe2(PIM)(Ph3CCO2)2] (1) and [Fe2(PIM)(ArTolCO2)2] (2), respectively. X-ray diffraction studies revealed that these diiron(II) complexes closely mimic the active site structures of the hydroxylase components of bacterial multi-component monooxygenases (BMMs), particularly the syn disposition of the nitrogen donor atoms and the bridging μ-η1η2 and μ-η1η1 modes of the carboxylate ligands at the diiron(II) centers. Cyclic voltammograms of 1 and 2 displayed quasi-reversible redox couples at +16 and +108 mV vs. ferrocene/ferrocenium, respectively. Treatment of 2 with silver perchlorate afforded a silver(I)/iron(III) heterodimetallic complex, [Fe2(μ-OH)2(ClO4)2(PIM)(ArTolCO2)Ag] (3), which was structurally and spectroscopically characterized. Complexes 1 and 2 both react rapidly with dioxygen. Oxygenation of 1 afforded a (μ-hydroxo)diiron(III) complex [Fe2(μ-OH)(PIM)(Ph3CCO2)3] (4), a hexa(μ-hydroxo)tetrairon(III) complex [Fe4(μ-OH)6(PIM)2(Ph3CCO2)2] (5), and an unidentified iron(III) species. Oxygenation of 2 exclusively formed di(carboxylato)diiron(III) compounds, a testimony to the role of the macrocylic ligand in preserving the dinuclear iron center under oxidizing conditions. X-ray crystallographic and 57Fe Mössbauer spectroscopic investigations indicated that 2 reacts with dioxygen to give a mixture of (μ-oxo)diiron(III) [Fe2(μ-O)(PIM)(ArTolCO2)2] (6) and di(μ-hydroxo)diiron(III) [Fe2(μ-OH)2(PIM)(ArTolCO2)2] (7) units in the same crystal lattice. Compounds 6 and 7 spontaneously convert to a tetrairon(III) complex, [Fe4(μ-OH)6(PIM)2(ArTolCO2)2] (8), when treated with excess H2O.
PMCID: PMC3149837  PMID: 21682286
18.  Benzannulated Tris(2-mercapto-1-imidazolyl)hydroborato Ligands: Tetradentate κ4–S3H Binding and Access to Monomeric Monovalent Thallium in an [S3] Coordination Environment 
The benzannulated tris(mercaptoimidazolyl)borohydride sodium complex, [TmButBenz]Na, has been synthesized via the reaction of NaBH4 with 1-tert-butyl-1,3-dihydro-2H-benzimidazole-2-thione, while [TmMeBenz]K has been synthesized via the reaction of KBH4 with 1-methyl-1,3-dihydro-2H-benzimidazole-2-thione. The molecular structures of the solvated adducts, {[TmButBenz]Na(THF)}2(μ-THF)2 and [TmMeBenz]K(OCMe2)3, have been determined by X-ray diffraction, which demonstrates that the [TmR] ligands in these complexes adopt different coordination modes to that in {[TmMeBenz]Na}2(μ-THF)3. Specifically, while the [TmMeBenz] ligand of the sodium complex {[TmMeBenz]Na}2(μ-THF)3 adopts a κ3-S3 coordination mode, the potassium complex [TmMeBenz]K(OCMe2)3 adopts a most uncommon inverted κ4-S3H coordination mode in which the potassium binds to all three sulfur donors and the hydrogen of the B–H group in a linear K•••H–B manner. Furthermore, the [TmButBenz] ligand of {[TmButBenz]Na(THF)}2(μ-THF)2 adopts a κ3-S2H coordination mode, thereby demonstrating the flexibility of this ligand system. The monovalent thallium compounds, [TmMeBenz]Tl and [TmButBenz]Tl, have been obtained via the corresponding reactions of [TmMeBenz]Na and [TmButBenz]Na with TlOAc. X-ray diffraction demonstrates that the three sulfur donors of the [TmRBenz] ligands of both [TmMeBenz]Tl and [TmButBenz]Tl chelate to thallium. This coordination mode is in marked contrast to that in other [TmR]Tl compounds, which exist as dinuclear molecules wherein two of the sulfur donors coordinate to different thallium centers. As such, this observation provides further evidence that benzannulation promotes κ3-S3 coordination in this system.
PMCID: PMC3912732  PMID: 24201311
19.  Tetra­kis(8-quinolinolato-κ2 N,O)hafnium(IV) dimethyl­formamide solvate monohydrate 
In the title compound, [Hf(C9H6NO)]·C3H7NO·H2O, the hafnium(IV) atom is coordinated by four 8-quinolinolate (Ox) ligands, forming a slightly distorted square-anti­prismatic coordination polyhedron. The crystal packing is controlled by O—H⋯O and C—H⋯O hydrogen-bonding inter­actions and π–π inter­actions between quinoline ligands of neighbouring mol­ecules. The inter­planar distances vary between 3.150 (1) and 3.251 (2) Å, while centroid–centroid distances vary from 3.589 (1) to 4.1531 (1) Å.
PMCID: PMC2979151  PMID: 21579072
20.  Bis[4-hy­droxy-3,5-dimeth­oxy­benzalde­hyde (2,4-dinitro­phen­yl)hydrazone] N,N-dimethyl­formamide disolvate monohydrate 
In the title compound, 2C15H14N4O7·2C3H7NO·H2O, the hydrazone mol­ecules are roughly planar, with the two benzene rings twisted slightly relative to each other by dihedral angle of 6.04 (11) and 7.75 (11)° in the two mol­ecules. The water mol­ecule is linked to the Schiff base mol­ecule by an O—H⋯O hydrogen bond. Intra­molecular N—H⋯O hydrogen bonds occur. In the crystal, mol­ecules are linked by inter­molecular N—H⋯O and O—H⋯O hydrogen bonds.
PMCID: PMC2983379  PMID: 21587615
21.  Pyruvic Oxime Nitrification and Copper and Nickel Resistance by a Cupriavidus pauculus, an Active Heterotrophic Nitrifier-Denitrifier 
The Scientific World Journal  2014;2014:901702.
Heterotrophic nitrifiers synthesize nitrogenous gasses when nitrifying ammonium ion. A Cupriavidus pauculus, previously thought an Alcaligenes sp. and noted as an active heterotrophic nitrifier-denitrifier, was examined for its ability to produce nitrogen gas (N2) and nitrous oxide (N2O) while heterotrophically nitrifying the organic substrate pyruvic oxime [CH3–C(NOH)–COOH]. Neither N2 nor N2O were produced. Nucleotide and phylogenetic analyses indicated that the organism is a member of a genus (Cupriavidus) known for its resistance to metals and its metabolism of xenobiotics. The microbe (a Cupriavidus pauculus designated as C. pauculus strain UM1) was examined for its ability to perform heterotrophic nitrification in the presence of Cu2+ and Ni2+ and to metabolize the xenobiotic phenol. The bacterium heterotrophically nitrified well when either 1 mM Cu2+ or 0.5 mM Ni2+ was present in either enriched or minimal medium. The organism also used phenol as a sole carbon source in either the presence or absence of 1 mM Cu2+ or 0.5 mM Ni2+. The ability of this isolate to perform a number of different metabolisms, its noteworthy resistance to copper and nickel, and its potential use as a bioremediation agent are discussed.
PMCID: PMC4279423  PMID: 25580463
22.  Discrete and Polymeric, Mono- and Dinuclear Silver Complexes of a Macrocyclic Tetraoxime Ligand with AgI–AgI Interactions 
Sensors (Basel, Switzerland)  2013;13(5):5671-5685.
Macrocyclic compounds that can bind cationic species efficiently and selectively with their cyclic cavities have great potential as excellent chemosensors for metal ions. Recently, we have developed a tetraoxime-type tetraazamacrocyclic ligand 1 formed through a facile one-pot cyclization reaction. Aiming to explore and bring out the potential of the tetraoxime macrocycle 1 as a chelating sensor, we report herein the preparation of several kinds of silver complexes of 1 and their unique coordination structures determined by single-crystal X-ray diffraction analyses. As a result, the formation of two kinds of discrete structures, monomeric complexes [Ag(1)X] (X = counter anions) and a dimeric complex [Ag2(1)2]X2, and two kinds of polymeric structures from a mononuclear complex, [Ag(1)]nXn, and from a dinuclear complex, [Ag2(1)X2]n, was demonstrated. In the resulting complexes, the structurally flexible macrocyclic ligand 1 was found to provide several different coordination modes. Notably, in some silver complexes of 1, AgI–AgI interactions were observed with different AgI–AgI distances which depend on the kind of counter anions and the chemical composition.
PMCID: PMC3690021  PMID: 23645105
silver; macrocycle; oxime; crystal; metal-metal interaction
23.  Synthesis, characterization and X-ray structural studies of four copper (II) complexes containing dinuclear paddle wheel structures 
Various dinuclear copper (II) complexes with octahedral geometry have been reported. The majority of these complexes contain N containing aromatic rings as axial ligands. There are also a few cases where the solvent used in the reaction occupies the axial position of the dinuclear copper (II) complex. This may occur by planned synthesis or some times by serendipity. Here we report some four copper (II) complexes containing solvent and or N containing heterocyclic ring as the axial ligand.
Four compounds, each containing dinuclear Copper (II) units (with the most robust, frequently occurring paddle wheel structures) were synthesized and characterised by single crystal X-ray diffraction and by IR spectroscopy. The compounds 1 & 2 have the general formula Cu2(RCOO) 4(L)2 [(for (1) RCOO= 4-Chloro Benzoate, L= Isopropanol; for 2 RCOO= Benzoate, L= 2-Amino-4,6-dimethyl pyrimidine )] while 3 & 4 have the general formula, Cu2(RCOO) 4(S)2 Cu2(RCOO) 4(L)2 [RCOO=5-Chloro-thiophene-2-carboxylate L= 2-Amino-4,6-dimethyl pyrimidine, for 3 S= ethanol; for 4 S= methanol ]. A wide range of hydrogen bonds (of the O-H…O, N-H…O and N-H…N type) and π-π stacking interactions are present in the crystal structures.
All compounds contain the dinuclear units, in which two Cu (II) ions are bridged by four syn, syn-η1:η1:μ carboxylates, showing a paddle-wheel cage type with a distorted octahedral geometry. The compounds 1 &2 contain a single dimeric unit while 3 &4 contain two dimeric units. The structures 3 and 4 are very interesting co-crystals of two paddle wheel molecules. Also it is interesting to note that the compounds 3 &4 are isostructural with similar cell parameters. Both the compounds 3 &4 differ in the solvent molecule coordinated to copper in one of the dimeric units. In all the four compounds, each of the copper dimers has an inversion centre. Every copper has a distorted octahedral centre, formed by four oxygen atoms (from different carboxylate) in the equatorial sites. The two axial positions are occupied by copper and the corresponding ligand.
PMCID: PMC3616956  PMID: 23433679
Paddle wheel structures; Cu (II) complexes; Supramolecular architectures; Carboxylates; Crystal structure
24.  Synthesis, characterization and crystal structure of a dinuclear iron nitrosyl complex with 2-mercapto-1-[2-(4-pyridyl)-ethyl]-benzimidazolyl 
Journal of molecular structure  2009;923(1-3):110-113.
A new dinuclear iron nitrosyl complex [Fe2(C14H12N3S)2(NO)4] (1) (C14H12N3S = 2-mercapto-1-[2-(4-pyridyl)-ethyl]-benzimidazolyl) has been obtained by the reaction of Fe(NO)2(CO)2 with 2-mercapto-1-[2-(4-pyridyl)-ethyl]-benzimidazole in CH3OH under moderate condition. Complex 1 was characterized by IR, UV-vis, electrochemistry and single crystal X-ray diffraction. IR spectrum displays two strong characteristic NO stretching frequencies (νNO) in solution and in solid state. Cyclic voltammetry shows one irreversible, two quasi-reversible and two reversible one-electron reductions and irreversible oxidizations. This result is consistent with the fact that complex 1 is very unstable and ready to lose NO in the air. As showing in the single crystal X-ray diffraction, complex 1 forms a “chair-shape” structure by the connections of two iron centers and S-C-N frames of benzimidazole. The dihedral angle of benzimidazole ring and 2Fe-2S plane is 73.6°. The crystal data are the following: 1, monoclinic, space group P2(1)/c, a = 10.43940(10) Å, b = 16.0900(2) Å, c = 10.13240(10) Å, α = 90°, β = 111.0940(10) °, γ = 90°, V = 1587.89(3) Å3, Z = 4.
PMCID: PMC2905046  PMID: 20640187
2-mercapto-1-[2-(4-pyridyl)-ethyl]-benzimidazole; dinuclear iron nitrosyl complex; infrared spectrum; electrochemistry; crystal structure
25.  Strain-Promoted Alkyne-Azide Cycloadditions (SPAAC) Reveal New Features of Glycoconjugate Biosynthesis 
We have shown that 4-Dibenzocyclooctynol (DIBO), which can easily be obtained by a streamlined synthetic approach, reacts exceptionally fast in the absence of a CuI catalyst with azido-containing compounds to give stable triazoles. Chemical modifications of DIBO, such as oxidation of the alcohol to a ketone, increased the rate of strain promoted azide-alkyne cycloadditions (SPAAC). Installment of a ketone or oxime in the cyclooctyne ring resulted in fluorescent active compounds whereas this property was absent in the corresponding cycloaddition adducts, thereby providing the first example of a metal-free alkyne-azide fluoro-switch click reaction. The alcohol or ketone functions of the cyclooctynes offer a chemical handle to install a variety of different tags, thereby facilitating biological studies. It was found that DIBO modified with biotin combined with metabolic labeling with an azido-containing monosaccharide can determine relative quantities of sialic acid of living cells that have defects in glycosylation (Lec CHO cells). A combined use of metabolic labeling/SPAAC and lectin staining of cells that have defects in the Conserved Oligomeric Golgi (COG) complex revealed that such defects have a greater impact on O-glycan sialylation than galactosylation, whereas sialylation and galactosylation of N-glycans was similarly impacted. These results highlight that the fidelity of Golgi trafficking is a critical parameter for the types of oligosaccharides that are being biosynthesized by a cell. Furthermore, by modulating the quantity of biosynthesized sugar nucleotide, cells may have a means to selectively alter specific glycan structures of glycoproteins.
PMCID: PMC3151320  PMID: 21661087
carbohydrates; glycoconjugates; click chemistry; azide; bioorthogonal

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