Showing papers in "Journal of Coordination Chemistry in 2016"

An unexpected dinuclear Cu(II) complex with a bis(Salamo) chelating ligand: synthesis, crystal structure, and photophysical properties

Abstract: An unexpected dinuclear Cu(II) complex, [Cu2(L2)2], has been synthesized via complexation of Cu(II) acetate monohydrate with a bis(Salamo) ligand H2L1. Catalysis of Cu(II) ions results in unexpected cleavage of two N–O bonds in H2L1, giving a dialkoxo-bridged dinuclear Cu(II) complex. Each Cu(II) complex possesses a Cu–O–Cu–O four-membered ring instead of the usual bis(Salamo) [Cu2L1] complex with H2L1. The H2L1 molecule is stabilized by intramolecular O1–H1⋯N1 hydrogen bonds and π⋯π stacking interactions linking adjacent molecules into a 1-D infinite zigzag chain. In the structure of the Cu(II) complex, intermolecular hydrogen bonds have stabilized the Cu(II) complex to form a self-assembling infinite 1-D linear chain. Furthermore, the H2L1 ligand shows intense photoluminescence with two emissions at ca. 370 and 464 nm upon excitation at 310 nm. The Cu(II) complex shows photoluminescence with maximum emission at ca. 423 nm upon excitation at 370 nm.

Mononuclear, homo- and hetero-binuclear complexes of 1-(5-(1-(2-aminophenylimino)ethyl)-2,4-dihydroxyphenyl)ethanone: synthesis, magnetic, spectral, antimicrobial, antioxidant, and antitumor studies

Abstract: A new Schiff base, H2L, was prepared by condensation of 4,6-diacetylresorcinol with o-phenylenediamine in molar ratio 1 : 1. The ligand reacted with copper(II), nickel(II), cobalt(II), iron(III), zinc(II), oxovanadium(IV), and dioxouranium(VI) ions in the absence and presence of LiOH to yield mononuclear and homobinuclear complexes. The mononuclear dioxouranium(VI) complex [(HL)-(UO2)(OAc)(H2O)]·5H2O was used to synthesize heterobinuclear complexes. The ligand and its metal complexes were characterized by elemental analyses, IR, 1H-, and 13C-NMR, electronic, ESR and mass spectra, conductivity, and magnetic susceptibility measurements as well as thermal analysis. In the absence of LiOH, mononuclear complexes (1, 4, and 9) were obtained; in the presence of LiOH, binuclear complexes (3, 5, 7, and 10) as well as mononuclear complexes (2, 6, and 8) were obtained. In the mononuclear complexes, the coordinating sites are the phenolic oxygen, azomethine nitrogen, and amino nitrogen. In addition to these c...

Salamo-type trinuclear and tetranuclear cobalt(II) complexes based on a new asymmetry Salamo-type ligand: syntheses, crystal structures, and fluorescence properties

Abstract: Two multinuclear Co(II) complexes, [{Co(L)(i-PrOH)}2Co(H2O)]∙2CH3CN (1) and [{Co(L)(μ-OAc)Co(MeOH)2}2]∙2CH3COCH3 (2), have been synthesized with a new asymmetric Salamo-type ligand (H3L = 6-hydroxy-6′-ethoxy-2,2′-[ethylenediyldioxybis(nitrilomethylidyne)]diphenol). The Co(II) complexes were obtained by different solvents, and the structures are completely different. In the Co(II) complex 1, the ratio of the ligand H3L to Co(II) atom is 2 : 3 and the Co(II) ions are all five-coordinate with trigonal bipyramidal geometries. In the Co(II) complex 2, the ratio of the ligand H3L to Co(II) atom is 2 : 4. Two central Co(II) ions are six coordinate with distorted octahedral geometries and two terminal Co(II) ions are five coordinate with distorted trigonal bipyramidal geometries. Self-assembling of an infinite 1-D supramolecular chain is formed by C–H⋯π interactions in 1. Interestingly, an infinite 2-D-layer plane structure is formed by the self-assembling array of 2 linked by C–H⋯π interactions. 1 and ...

Zinc and cobalt complexes with (2-carboxyphenoxy) acetic acid ligand: syntheses, structures, fluorescent and magnetic properties

Abstract: Four binary compounds, [Zn(cpa)(H2O)3] (1), [Co(cpa)(H2O)3] (2), [Zn(cpa)(H2O)]n, (3) and [Co(cpa)(H2O)]n (4) (H2cpa = (2-carboxyphenoxy)acetic acid), have been synthesized and structurally characterized. In mononuclear 1 or 2, the metal ion (ZnII for 1 and CoII for 2) is surrounded by three water molecules and one tridentate chelate cpa2− in a distorted octahedral geometry, while in 3 or 4, the central metal ion (ZnII for 3 and CoII for 4) is located in a deformed square–pyramid formed by one water and two cpa2−. Each cpa2− is chelate bridging μ2 coordination and forms a 1-D zigzag chain structure 2 or 3. The different synthesis conditions for 1–4 have been carefully discussed. The solid-state fluorescence measurements for 1 and 3 together with magnetic properties for 4 also have been investigated.

Review: Graphene-supported coordination complexes and organometallics: properties and applications

Abstract: Recent advances in the functionalization of graphene (G) and graphene oxide (GO) using classical coordination complexes, as well as σ- and π-organometallic compounds as precursors, are discussed. Graphene can form hybrids via covalent or non-covalent interactions with metal complexes of carboxylates, amines, polypyridine compounds, a host of N,O-containing ligands, porphyrins, phthalocyanines, carbonyls, cyclopentadienyls, pyrene-containing moieties, and other aromatic structures. The hybrid constructs are interesting for applications in catalysis, energy storage, and corrosion inhibition and present interesting possibilities of modulating the electronic structure of graphene.

Synthesis, characterization and antimicrobial activity of zinc(II) ibuprofen complexes with nitrogen-based ligands

Abstract: Metal carboxylate complexes possess different carboxylate coordination modes, e.g. monodentate, bidentate, and bridging bidentate. Five Zn(II) complexes were prepared and characterized in order to examine their coordination modes in addition to their biological activity. The syntheses were started by preparation of [Zn(ibup)2(H2O)2] (1). Then, different nitrogen-donor ligands reacted with 1 to produce [Zn(ibup)2(2-ampy)2] (2), [Zn(ibup)(2-ammethylpy)] (3), [Zn(ibup)(2,2′-bipy)] (4), and [Zn2(ibup)4(2-methylampy)2] (5) (ibup = ibuprofen, 2-ampy = 2-aminopyridine, 2-ammethylpy = 2-aminomethylpyridine, 2,2′-bipy = 2,2′-bipyridine, 2-methylampy = 2-(methylamino)pyridine). IR, 1H NMR, 13C{1H}-NMR and UV–vis spectroscopies were used for characterization. The crystal structures of 2 and 5 were determined by single-crystal X-ray diffraction. Investigation of in vitro antibacterial activities for the complexes against Gram-positive (Micrococcus luteus, Staphylococcus aureus and Bacillus subtilis) and Gram-...

Evaluating silicene as a potential cathode host to immobilize polysulfides in lithium–sulfur batteries

Abstract: The internal shuttle effect caused by polysulfides dissolution and migration negatively impacts lithium–sulfur battery performance. In this work, a mesoscale simulation strategy, which involves atomistic calculation and coarse-grained molecular modeling, is employed to evaluate silicene as a potential cathode host material to immobilize polysulfides. Adsorption energies of insoluble polysulfides (Li2Sx with x = 1, 2) and soluble polysulfide Li2S4 on pristine and doped silicene sheets are calculated. Results show that the adsorption is thermodynamically favorable and N-doped silicene is helpful in trapping intermediate discharge products, Li2S2 and Li2S4. The dissociation and reduction of long-chain polysulfides to short-chain polysulfides are observed. Electronic structure analysis shows that Li2Sx molecules interact with silicene via strong chemical bonds. The atomistic structure evolution of Li2S layer formation on silicene is also investigated in this study. It is found that Li2S (110) layer ...

CO-releasing properties and anticancer activities of manganese complexes with imidazole/benzimidazole ligands

Abstract: Carbon monoxide (CO) is an important signaling molecule which plays significant roles in the pathogenesis of cancer. CO is produced by enzymatic degradation of heme in mammals. Heme oxygenase 1 (HO-1) catalyzes the breakdown of heme into CO, ferrous iron, and biliverdin. CO induces HO-1 and inhibits cell proliferation. Cancer cells exposed to several stress factors (hypoxia, reactive oxygen species, cis-platin, and oxidative stress), and HO-1 displays cytoprotective role against oxidative stress and inhibits apoptosis, metastases, angiogenesis, and cell proliferation processes. Therefore, metal containing CO-releasing molecules (CORMs) have been designed as an effective cancer treatment strategy. CORMs are responsible for releasing controlled amounts of CO to cells and tissues. Thus, we synthesized [Mn(CO)3(bpy)L]X manganese containing CORMs [bpy = 2,2′-bipyridine, X = hexafluorophosphate (PF6), trifluoromethanesulfonate (OTf), L = imidazole, methylimidazole, benzimidazole, N-benzylbenzimidazole, ...

A new member of the cationic dinitrosyl iron complexes family incorporating N-ethylthiourea is effective against human HeLa and MCF-7 tumor cell lines

Abstract: A new analog of the active site of mononuclear dinitrosyl [1Fe–2S] proteins, [C3N2H8SFe(NO)2Cl][Fe(NO)2(C3N2H8S)2]+Cl− (I), has been synthesized by reacting NO with an aqueous mixture of iron(II) sulfate and N-ethylthiourea in acidic medium. The structure and properties of the complex were studied by X-ray diffraction, IR, Mossbauer, and EPR spectroscopy, in addition to quantum chemical calculations. Complex I spontaneously generates NO in protic media. The cytotoxicity of I was investigated against human cervical carcinoma (HeLa), breast cancer (MCF7), and non-immortalized (FetMCS) cell lines. The cytotoxicity of I against HeLa is similar to that of anticancer agents currently used clinically (platinum complexes), but I is 10 times less toxic in normal cells. The cytotoxicity of MCF7 cells to I is low.

Syntheses, characterization, and antimicrobial properties of nickel(II) dithiocarbamate complexes containing NiS4 and NiS2PN moieties

Abstract: Three Ni(II) dithiocarbamate complexes, [Ni(buphdtc)2] (1), [Ni(buphdtc)(PPh3)(NCS)] (2) and [Ni(buphdtc)(PPh3)(NC)] (3) (where bu = butyl and ph = phenyl), were synthesized and characterized by elemental analysis, UVvis, and FTIR spectroscopies. Complexes 1 and 2 were further characterized by single-crystal X-ray structural analysis. The single-crystal X-ray structural analysis indicates a slightly distorted square planar geometry. In 2 and 3, the influences of the auxiliary ligands (PPh3, NCS, and NC) on their steric and electronic properties were observed. Thermal studies of the complexes showed decomposition starting at 250–300 °C, leading to formation of nickel sulfide phases around 400 °C. The complexes were screened against some bacteria strains, Staphylococcus aureus, Streptococcus pneumoniae, Bacillus subtilis, Escherichia coli, Klebsiella oxytoca and Pseudomonas aeruginosa, and two fungi species, Aspergillus niger and Fusarium oxysporum. The complexes showed moderate-to-strong antimicrob...

Hetero-trinuclear Zn(II)-M(II) (M = Sr, Ba) complexes based on a mononuclear Zn(II) complex metallohost: syntheses, structures and fluorescence properties

Abstract: A new mononuclear Zn(II) complex, [ZnL(HOAc)] (1) (H2L = 6,6′-diethoxy-2,2′-[1,2-ethylenedioxybis(nitrilomethylidyne)]diphenol), was synthesized by reaction of H2L and Zn(II) acetate under solvothermal conditions. Complex 1 acts as a metallohost possessing a pentadentate O5 donor. Complex 1 molecules bonded to one Sr(II) or Ba(II) form two new hetero-trinuclear complexes, [(ZnL)2M(OAc)2] (M = Sr (2), Ba (3)). In 2 and 3, Zn(II) ions are 5-coordinate, but the Sr(II) or Ba(II) ion is 10-coordinate by four μ-phenolic oxygens from two L2− units, four oxygens from four ethoxy groups and two oxygens from two μ-acetato ligands. Furthermore, 1–3 exhibit blue emissions with the maximum emission wavelengths λmax = 477, 500, and 471 nm when excited at 360 nm.

Affinity of a new copper(II) complex to DNA/BSA and antioxidant/radical scavenging activities: crystal structure of [Cu(4,7-diphenyl-1,10-phenanthroline)(leucine)(NO3)(H2O)]

Abstract: A new copper(II) complex, [Cu(Bphen)(Leu)(NO3)(H2O)] (Bphen = 4,7-diphenyl-1,10-phenanthroline, leu = L-leucine), has been synthesized and characterized by IR spectroscopy, CHN analysis, and single-crystal X-ray diffraction techniques. The CT-DNA binding properties of the complex have been investigated by both absorption and emission spectroscopy. The binding parameters for the fluorescence Scatchard plot were also determined. Further, the interaction of the complex with bovine serum albumin (BSA) has been investigated using absorption and emission spectroscopy. The thermodynamic parameters, free energy change (ΔG), enthalpy change (ΔH), and entropy change (ΔS), were calculated by the van’t Hoff equation and discussed. The distance between BSA and the complex has been obtained according to fluorescence resonance energy transfer. Conformational changes of BSA have been observed from synchronous fluorescence. Antioxidant and radical scavenging activities of the complex were determined by various in ...

Synthesis, crystal structure and DFT calculations of octahedral nickel(II) complexes derived from N′-[(E)-phenyl(pyridin-2-yl)methylidene]benzohydrazide

Abstract: The two new nickel(II) complexes, [Ni(HL)(L)](NO3)∙H2O (1) and [Ni(L)2] (2) (where HL/L = N′-[(E)-phenyl(pyridin-2-yl)methylidene]benzohydrazide), have been synthesized and characterized by elemental analysis, spectroscopic, magnetic susceptibility, and cyclic voltammetric measurements. Single-crystal X-ray analysis of [Ni(HL)(L)](NO3)∙H2O (1) and [Ni(L)2] (2) has revealed the presence of a distorted octahedral geometry around nickel(II). The X-ray and spectral characterizations have confirmed the existence of the keto-enol form of the ligands in the complexes. The electronic structures and spectral properties of the ligands and the complexes have been explained by DFT and TDDFT calculations. Superoxide dismutase activity of these complexes has also been measured.

Preparation, structure and photocatalysis of metal-organic frameworks derived from aromatic carboxylate and imidazole-based ligands

Abstract: Three 3-D metal-organic frameworks (MOFs), [Cd(NDC)(biim-4)]·0.5H2O (1), [Cd2(TDC)2(biim-4)2(H2O)2] (2) and [Zn2(biim-4)2(TDC)2]·2.5H2O (3) (biim-4 = 1,4-bis(1-imidazolyl) butyric alkyl; H2NDC = 1,4-naphthalene dicarboxylic acid; H2TDC = thiophene-2,5-dicarboxylic acid), have been synthesized under hydrothermal conditions and structurally characterized by single X-ray diffraction. The three MOFs have high photocatalytic degradation effects on methyl orange under UV irradiation. Through electronic structure analysis combined with time-dependent density functional theory calculations, catalytic performances of these materials are correlated with the molecular composition and the optoelectronic properties of the samples.

Synthesis, characterization, and cytotoxic and antimicrobial activities of ruthenium(II) arene complexes with N,N-bidentate ligands

Abstract: Three new complexes, [(η6-C6H6)RuCl(C5H4N-2-CH=N-Ar)]PF6 (Ar = phenylmethylene (1), (4-methoxyphenyl)methylene (2), and phenylhydrazone (3)), were prepared by reacting [(η6-C6H6)Ru(μ-Cl)Cl]2 with N,N′-bidentate ligands in a 1 : 2 ratio. Full characterization of the complexes was accomplished using 1H and 13C NMR, elemental and thermal analyses, UV–vis and IR spectroscopy and single crystal X-ray structures. Single crystal structures confirmed a pseudo-octahedral three-legged, piano-stool geometry around Ru(II), with the ligand coordinated to the ruthenium(II) through two N atoms. The cytotoxicity of the mononuclear complexes was established against three human cancer cell lines and selectivity was also tested against non-cancerous human epithelial kidney (HEK 293) cells. The compounds were selective toward the tumor cells in contrast to the known anti-cancer drug 5-fluoro uracil which was not selective between the tumor cells and non-tumor cells. All the compounds showed moderate activity against ...

Synthesis, crystal structures, antioxidant activities, and DNA-binding studies of two silver(I) complexes with 1,3-bis(1-ethylbenzimidazol-2-yl)-2-thiapropane, and α,β-unsaturated carboxylates

Abstract: Two new ternary complexes of silver(I) with 1,3-bis(1-ethylbenzimidazol-2-yl)-2-thiapropane (bebt) and two ·α,β-unsaturated carboxylates, [Ag(bebt)(crotonate)] (1) and [Ag(bebt)2](o-coumarate)·CH3CN·2C2H5OH (2), have been synthesized, and characterized by physicochemical and spectroscopic methods. Single-crystal X-ray diffraction revealed that the coordination environment of 1 can be described as trigonal planar, while 2 has a distorted tetrahedral geometry. Experimental studies of the DNA-binding properties indicated that the free ligand and both complexes bind to DNA via intercalation, and the order of the binding affinity is 1 > bebt > 2. Antioxidant activity experiments show that 2 possesses significant antioxidant activity against hydroxyl radicals, with more efficient hydroxy radical scavenging compared with mannitol and vitamin C.

Synthesis, structure and spectroscopic studies on DNA binding, BSA interaction of a nickel(II) complex containing l–methionine Schiff base and 1,10-phenanthroline

Abstract: A new nickel(II) complex, [Ni(o-van-L-met)(phen)(CH3OH)] (o-van-L-met = Schiff base derived from o-vanillin and l-methionine, phen = 1,10–phenanthroline), has been synthesized and characterized by elemental analyses, IR spectra, and single-crystal X-ray diffraction. The crystal structure shows nickel is six-coordinate in a distorted octahedral geometry. In this crystal, molecules form a 2-D plane structure via hydrogen bonds and π–π interactions. The interaction of the complex with calf thymus DNA (CT-DNA) was investigated by absorption, fluorescence, circular dichroism (CD), spectroscopies, and viscosity measurement. The complex binds to CT-DNA in an intercalative mode with a binding constant of (4.7 ± 0.5) × 104 M−1. The interaction of the complex with bovine serum albumin (BSA) was also studied by the multispectroscopic methods. Results illustrated that the nickel(II) complex can effectively quench the intrinsic fluorescence of BSA via a static quenching mechanism and cause conformational chang...

Synthesis, structural characterization, in vitro cytotoxicities, and BSA interaction of di-organotin(IV) complexes derived from salicylaldehyde nicotinoyl hydrazone

Abstract: Two organotin(IV) compounds were synthesized from salicylaldehyde nicotinoyl hydrazone and the corresponding dialkyltin(IV) precursor. Their structures were determined by IR, elemental analysis, NMR, and single crystal X-ray diffraction analysis. Compound 1 exhibits a distorted trigonal bipyramidal geometry around tin, which is coordinated to the Schiff-base ligand in an enolic tridentate fashion. For 2, structural analysis reveals that it is a centro-symmetric trimer, in which the central Sn adopts a six-coordinate octahedral geometry and the other two Sn ions adopt five-coordinate trigonal bipyramidal geometry. In vitro cytotoxicities of the compounds against three human cisplatin-resistant tumor cell lines (A549, HeLa, and MCF-7) were assessed by MTT assay. Further, the interaction of 1 and 2 with bovine serum albumin (BSA) has been explored by the titration method with fluorescence quenching spectra and synchronous fluorescence spectra. Studies reveal that di-n-butyltin(IV) complex 1 with signi...

Coordination compounds based on CAPh type ligand: synthesis, structural characteristics and luminescence properties of tetrakis-complexes CsLnL4 with dimethylbenzoylamidophosphate

Abstract: Searching for prospective luminescent materials, the series of new lanthanide coordination compounds CsLnL4 (Ln = La, Pr, Nd, Sm – Er, and Yb; L− = {C6H5CONPO(OCH3)2}-) was synthesized. X-ray diffraction studies of CsNdL4 and CsYbL4 have been performed establishing polymeric structures of the tetrakis-complexes built from [LnL4]− anions and cesium cations functioning as linkers. The IR, absorption, emission, excitation spectra, and decay time measurements at 298 and 77 K, as well as thermal gravimetric analyses, were used to characterize the complexes.

Synthesis, spectral, DFT, and antimicrobial studies of tin(II) and lead(II) complexes with semicarbazone and thiosemicarbazones derived from (2-hydroxyphenyl)(pyrrolidin-1-yl)methanone

Abstract: A new series of metal complexes [M(L)2] (where M = Sn(II), Pb(II), and HL = semicarbazone, thiosemicarbazone or phenylthiosemicarbazone) have been prepared and characterized by elemental analysis, conductance measurements, molecular weight determinations, UV–visible, infrared, and nuclear magnetic resonance (1H-, 13C-, and 119Sn-NMR) spectral studies. Elemental analysis of the metal complexes suggested 1 : 2 (metal–ligand) stoichiometry. Infrared spectra of the complexes agree with coordination to the metal through the nitrogen of the azomethine (>C=N−) and the oxygen/sulfur of the ketonic/thiolic group. Electronic spectra suggest a distorted tetrahedral geometry for all Schiff base complexes. The bond lengths, bond angles, highest occupied molecular orbital, lowest unoccupied molecular orbital, Mulliken atomic charges, and the lowest energy model structure of the complexes have been determined with DFT calculations. Representative Schiff base and its metal chelates have been screened for their in...

Synthesis, crystal structures, and DNA-binding studies of two silver(I) complexes with 1,3-bis(1-ethylbenzimidazol-2-yl)-2-thiapropane

Abstract: Two new silver(I) complexes, [Ag(bebt)(methacrylate)] (1) and [Ag2(bebt)2](pic)2 (2) (bebt = 1,3-bis(1-ethylbenzimidazol-2-yl)-2-thiapropane, pic = picrate), have been synthesized and characterized by physico-chemical and spectroscopic methods. Single-crystal X-ray diffraction revealed that the structure of 1 was four-coordinate in a distorted tetrahedral geometry, while in 2, it may be described as a 2 + 1 coordinated silver(I) compound with a nearly linear N–Ag–N backbone and a weak Ag–S interaction. Two ligands are arranged in a face-to-face syn conformation to coordinate to two Ag(I) ions from opposite directions in 2, generating a U-type double layer structure around the metal ions. Experimental studies of the DNA-binding properties indicated that free bebt and both complexes bind to DNA via intercalation, and the order of the binding affinity is 2 > 1 > bebt.

Photo-responsive azo MOF exhibiting high selectivity for CO2 and xylene isomers

Abstract: A combination of azo and acylamide ligands is used in the preparation of metal–organic frameworks. Light response research reveals that under UV–vis irradiation, the CO2 adsorption of 1 declines as much as 21.4%. 1 exhibits excellent CO2 adsorption selectivity over CH4, O2, CO, and N2 gasses with IAST selectivity of 21–580 at 293 K. This MOF also has promising potential in separation of xylene isomers in the liquid phase with the adsorption of p-xylene of 265.15, o-xylene of 101.25 and m-xylene of 0 mg g−1, respectively.

Synthesis, characterization, and catalytic activity of supported molybdenum Schiff base complex as a magnetically recoverable nanocatalyst in epoxidation reaction

Abstract: A heterogeneous nanocatalyst was prepared via covalent anchoring of dioxomolybdenum(VI) Schiff base complex on core–shell structured Fe3O4@SiO2. The properties and the nature of the surface-fixed complex have been identified by a series of characterization techniques such as SEM, EDX, XRD, TGA, FT-IR, and VSM. The synthesized hybrid material was an efficient nanocatalyst for selective oxidation of olefins to corresponding epoxides with t-BuOOH in high yields and selectivity. The catalyst could be conveniently recovered by applying an external magnetic field and reused several times without significant loss of efficiency.

Synthesis and characterization of diiron ethanedithiolate complexes with monosubstituted phosphine ligands

Abstract: Reactions of (μ-edt)Fe2(CO)6 (edt = SCH2CH2S) (1) with the monophosphine ligands Ph2PCH2Ph, Ph2PC6H11, Ph2PCH2CH2CH3, or P(2-C4H3O)3 in the presence of Me3NO∙2H2O afforded (μ-edt)Fe2(CO)5L [L = Ph2PCH2Ph, 2; Ph2PC6H11, 3; Ph2PCH2CH2CH3, 4; P(2-C4H3O)3, 5] in 70–88% yields. Complexes 2–5 were characterized by spectroscopy and single crystal X-ray diffraction analysis. The phosphorus of 2–5 is in an apical position of the distorted octahedral geometry of iron.

New copper(II) complexes including pyridine-2,5-dicarboxylic acid: synthesis, spectroscopic, thermal properties, crystal structure and how these complexes interact with purified PON 1 enzyme

Abstract: We report the synthesis of two square-pyramidal copper(II) complexes, [Cu(2,5-pydc)(2-aepy)(H2O)]·H2O, 1, and [Cu(2,5-pydc)(2-ampy)(H2O)]·H2O, 2 (2-aepy = 2-(aminoethyl)pyridine, 2-ampy = 2-(aminomethyl)pyridine, 2,5-pydc = pyridine-2,5-dicarboxylic acid or isocinchomeronic acid). The synthesized complexes have been characterized by X-ray diffraction, FT-IR, elemental, and thermal analysis techniques. The crystal structure of 1 was established by X-ray analysis. Powder X-ray diffraction analysis showed that the complexes are pure. The inhibition of human serum paraoxonase 1 (PON 1, EC 3.1.8.1) enzyme with these complexes were investigated. We used diethyl 4-nitrophenyl phosphate as a substrate to measure the paraoxonase activity of PON 1 enzyme spectrophotometrically. Complexes 1 and 2 decreased the in vitro PON 1 activity with different inhibition mechanisms. Complexes 1 and 2 inhibited paraoxonase activity of this enzyme as competitively and noncompetitively, respectively.

Thiophene-Based Fluorescent Mercury-Sensors

Abstract: Coordination chemistry of thiophene rings is poorly understood, despite their common use in organic electronic materials. The absorption and emission responses to transition metal ions of three thiophene-based ligands containing pyridine chelating groups are examined. These ligands, 2-(2′-thienyl)-pyridine (L1), 2,5-bis(2-pyridyl)thiophene (L2), and 2,6-bis(2-thienyl)pyridine (L3), show a ratiometric fluorescence response in the presence of Hg(ClO4)2 with reasonable selectivity against many transition metal ions in acetonitrile. 1H NMR data support S,N chelation of L1 and L2 to the Hg(II) center, while L3 coordinates through cyclometalation via one carbon of thiophene. DFT calculations suggest thiophene coordinates to Hg(II) in a bent geometry. Our results indicate that thiophene could offer selectivity for Hg(II) towards the design of fluorescent sensors.

Syntheses, crystal structures, and DNA-binding properties of two nickel(II) complexes with 1,3-bis(benzimidazol-2-yl)-2-oxapropane derivatives

Abstract: [Ni(obb)(DMF)2(H2O)]·(Pic)2·05DMF (1) and [Ni(Etobb)2]·(Pic)2·2DMF (2) (obb = 1,3-bis(benzimidazol-2-yl)-2-oxapropane, Etobb = 1,3-bis(1-ethylbenzimidazol-2-yl)-2-oxapropane, Pic = picrate) have been synthesized and characterized by physicochemical and spectroscopic methods The structures of both complexes have been determined by X-ray single-crystal diffraction The coordination geometries of 1 and 2 can be described as distorted octahedra The interaction of the nickel(II) complexes with calf thymus DNA was investigated by electronic absorption, fluorescence spectroscopy, and viscosity measurements The experimental results suggest that 1 and 2 bind to DNA in an intercalation mode, and their binding affinity for DNA follows the order 1 > 2 DNA-binding behaviors can be attributed to the large coplanar aromatic rings in the V-shaped ligand and steric hindrance

Synthesis, characterization and antimicrobial activity of a bidentate NS Schiff base of S-benzyl dithiocarbazate and its divalent complexes

Abstract: The reaction of S-benzyl dithiocarbazate (SBDTC) with 2,4,5-trimethoxybenzaldehyde afforded a bidentate NS Schiff base 1 (benzyl-3-N-(2,4,5-trimethoxyphenylmethylenehydrazine carbodithioate), which on further reaction with M(II) (where M(II) = nickel(II), zinc(II), palladium(II) and copper(II)) in ethanol under reflux yielded bis-chelated inner complexes [ML2] 2–5 with deprotonated L. The ligand and its complexes were characterized by physicochemical techniques, viz., molar conductance, magnetic susceptibility measurement, IR, NMR, UV–Vis and mass spectroscopic techniques. The crystal structures of 1 and 5 were also determined by single-crystal X-ray crystallography. The crystal structure analysis showed that the ligand exists in its thione tautomeric form. In the complexes, each of the two deprotonated ligands chelated the metal ions through the β-nitrogen and the thione sulfur forming five-membered rings. The copper(II) complex (5) exhibited a square-planar geometry, where the two N2S2 chromopho...

Synthesis, structure and methyl methacrylate polymerization of cobalt(II), zinc(II) and cadmium(II) complexes with N,N′,N-bidentate versus N,N′,N-tridentate N,N′,N-bis((1H-pyrazol-1-yl)methyl)amines

Abstract: Mononuclear Co(II), Zn(II) and Cd(II) complexes derived from bidentate or tridentate N,N′,N-bis((1H-pyrazol-1-yl)methyl)amines (Ln = LA, LB), where LA is N,N-bis((1H-pyrazol-1-yl)methyl)-3-methoxypropan-1-amine and LB is 3-methoxy-N,N-bis((3,5-dimethyl-1H-pyrazol-1-yl)methyl)propan-1-amine, have been synthesized and characterized. The geometry at Co(II) and Cd(II) for [LACoCl2], [LBCoCl2] and [LBCdBr2] with N,N′,N-tridentate ligands (Ln = LA, LB) can be described as a distorted trigonal bipyramid achieved by coordinative interaction of Npyrazole, two halides and the nitrogen of amine moiety. However, the molecular structure of four-coordinate [LAZnCl2] can be best described as tetrahedral, resulting in an eight-membered chelate ring. [LACoCl2] polymerized methyl methacrylate in the presence of modified methylaluminoxane at 60 °C and resulted in poly(methylmethacrylate) (PMMA) with higher molecular weight and narrower polydispersity index compared to the other synthesized complexes. However, all th...

Homobimetallic zinc(II) dithiocarbamates: synthesis, characterization and in vivo antihyperglycemic activity

Abstract: This article presents structural characteristic and in vivo antihyperglycemic activities of three new homobimetallic Zn(II) dithiocarbamates (1–3) with general formula [ZnL2]2, where L is 4-(3-methoxyphenyl)piperazine-1-carbodithioate (1), 4-(4-methoxyphenyl)piperazine-1-carbodithioate (2) and 4-benzhydrylpiperazine-1-carbodithiaoate (3). These complexes have been characterized by elemental analysis, FT-IR, multinuclear NMR (1H and 13C), and X-ray single crystal analysis. The latter technique has confirmed the homobimetallic nature of 1 and 2 in which Zn ions are linked via sulfurs to form a four-membered ring Zn2S2. Non-covalent intermolecular interactions give a supramolecular ladder-like zigzag chain (1) and layered structure (2). The antihyperglycemic activities revealed that the blood glucose lowering ability follows the trend: glibenclamide (83.0 mg dL−1) > 3 (97.6 mg dL−1) > 2 (100.4 mg dL−1) > 1 (141.4 mg dL−1).