Distorted Octahedron Geometry Research Articles

Biological Activity of Novel Organotin Compounds with a Schiff Base Containing an Antioxidant Fragment.

A series of novel organotin(IV) complexes on the base of 2-(N-3',5'-di-tert-butyl-4'-hydroxyphenyl)-iminomethylphenol (L) of formulae Me2SnBr2(L)2 (1), Bu2SnCl2(L)2(2), Ph2SnCl2(L) (3), Ph2SnCl2(L)2 (4) Ph3SnBr(L)2 (5) were synthesized and characterized by 1H, 13C, 119Sn NMR, IR, ESI-MS and elemental analysis. The crystal structures of initial L and complex 2 were determined by XRD method. It was found that L crystallizes in the orthorhombic syngony. The distorted octahedron geometry around Sn center is observed in the structure of complex 2. Intra- and inter-molecular hydrogen bonds were found in both structures. The antioxidant activity of new complexes as reducing agents, radical scavengers and lipoxygenase inhibitors was estimated spectrophotometrically in CUPRAC and DPPH tests (compounds 1 and 5 were found to be the most active in both methods), and in the process of enzymatic oxidation in vitro of linoleic acid under the action of lipoxygenase LOX 1-B (EC50 > 33.3 μM for complex 2). Furthermore, compounds 1-5 have been investigated for their antiproliferative activity in vitro towards HCT-116, MCF-7 and A-549 and non-malignant WI-38 human cell lines. Complexes 2 and 5 demonstrated the highest activity. The plausible mechanisms of the antiproliferative activity of compounds, including the influence on the polymerization of Tb+MAP, are discussed. Some of the synthesized compounds have also actively induced apoptosis and blocked proliferation in the cell cycle G2/M phase.

Channel regulation through solvents for Cd‐MOFs based on p‐methoxyphenyl imidazole dicarboxylate: Synthesis, crystal structure, fluorescence, and explosive identification

AbstractUnder different solvent systems, the reaction of Cd(NO3)2·4H2O with 2‐p‐methoxyphenyl‐1H‐imidazole‐4,5‐dicarboxylic acid (p‐H3MOPhIDC) ligand produce two new Cd‐MOFs, [Cd(p‐HMOPhIDC)(C2H5OH)]n (1) and [Cd2(p‐HMOPhIDC)2(Py)(C2H5OH)]n (2). Structural analysis shows that although the two Cd‐MOFs have the same six‐coordinated distorted octahedron geometry of the Cd(II) centers and the similar framework structure, they have different coordinated polymerization unit symmetry and internal environment in the channels. Among them, the polymerization unit in the channel of Cd‐MOFs 1 is centrosymmetric, while the polymerization unit in the channel of Cd‐MOFs 2 is asymmetric. Compared with the free p‐H3MOPhIDC ligand, the fluorescence peaks of the two Cd‐MOFs in the solid‐state have undergone a slightly red shift and enhancement. This is due to the increased rigidity of the ligand after the coordination of the metal ions with the ligand, which reduces the energy loss of thermal vibration. The fluorescence enhancement of Cd‐MOFs 1 is greater than that of 2, which is related to the symmetry of the coordination polymerization units in the two Cd‐MOFs channels. In addition, Cd‐MOFs 2 can highly sensitive sense 2,4‐dinitrotoluen (DNP) and 2,4,6‐trinitrophenol (TNP) through luminescence quenching effect, whereas 1 cannot. This result is due to the difference in the environment within their channels.

Syntheses, Structures, Magnetic Properties and Antibacterial Activities of Two Copper(II) Azido Complexes with Varied Nuclearities Containing Symmetrical 1,3-Diammine as Chelator

Two copper(II) azido complexes of the types mononuclear [Cu(TMEDA)2(N3)2] (1) and dinuclear [Cu(TMEDA)(μ1,1-N3)(N3)]2 (2) [TMEDA = trimethylenediamine; N3 – = azide ion] have been synthesized and characterized. X-ray structural analysis revealed that each copper(II) center in complex 1 adopts a distorted octahedron geometry with a CuN6 chromophore ligated through four N atoms of two different symmetrical TMEDA ligands as bidentate chelator and two N atoms of two terminal azides. In complex 2, each copper(II) center adopts a distorted square pyramidal geometry with a CuN5 chromophore ligated through two N atoms of TMEDA as bidentate chelator and two N atoms of two different azides as μ1,1-N3 bridging mode and one N atom of terminal azide ion. The two copper centers are connected through double μ1,1-N3 bridges affording a dinuclear structure with Cu···Cu separation 3.327(2) Å. In crystalline state, mononuclear units in complex 1 are associated through intermolecular N-H···N and C-H···N hydrogen bonds to form a 2D sheet structure viewed along crystallographic b-axis, whereas dinuclear entities in complex 2 are propagated through intermolecular N-H···N and C-H···N hydrogen bonds to form a 3D network structure viewed along crystallographic a-axis. The Variable-temperature magnetic susceptibility measurement evidenced a dominant antiferromagnetic interaction between the metal centers through μ1,1-azide bridges in complex 2 with J = − 0.40 cm-1. The antibacterial activities of the complexes have also been studied.

New heteroleptic lanthanide complexes as multimodal drugs: Cytotoxicity studies, apoptosis, cell cycle analysis, DNA interactions, and protein binding

We report herein the synthesis and characterization of four new heteroleptic complexes of Sm(III), Eu(III), Gd(III), and Tb(III) with the natural flavonoid 5‐hydroxyflavone (primuletin) and 1,10‐phenanthroline. According to the physicochemical characterization, the mononuclear complexes correspond to the general formula [Ln(OH)2L1L2]·nH2O, where L1 = C15H9O3 (deprotonated 5‐hydroxyflavone) and L2 = C12H8N2 (1,10‐phenanthroline), Ln is the lanthanide cation, and n = 4 for Sm(III), 3.5 for Eu(III), 2 for Gd(III), and 3 for Tb(III). A six‐coordinated distorted octahedron geometry was proposed for the complexes, and density functional theory (DFT) studies were used to calculate their optimized geometry. Cytotoxicity was studied using MTS assay on cervical, colorectal, colon, breast, and ovarian adenocarcinoma cell lines. Flow cytometry data were consistent with apoptotic cell death and disruption of the cell cycle in cervical and colon cancer cells. As a means to investigate the mechanism underlying the cytotoxic effects, the abilities of the complexes to interact with calf thymus DNA, human serum albumin, and transferrin have also been assessed. According to experimental and computational studies, the four lanthanide complexes act as DNA intercalators and bind strongly to serum proteins.

Synthesis, crystal structure, Hirshfeld surface analysis, DNA binding, DNA cleavage activity and molecular docking of a new Schiff base nickel(II) complex

A mononuclear nickel(II) complex, [Ni(o-van-tris)2]·2H2O (o-van-tris = Schiff base derived from o-vanillin and tris(hydroxymethyl)aminomethane), has been synthesized and structurally characterized. The single crystal structure shows a distorted octahedron geometry coordinated with Ni(II) atom, and 2 D plane structure has formed by O–H···O hydrogen bond interactions. An analysis to ascertain intermolecular interactions of the complex was performed based on the Hirshfeld surfaces and their associated two-dimensional fingerprint plots. The binding properties of the nickel(II) complex with CT-DNA have been investigated by spectroscopic methods and molecular docking. Absorption and fluorescence spectral studies reveal that the complex interacts with DNA through hydrogen bond and hydrophobic interactions with the DNA base pairs. Molecular docking studies show that the complex effectively docks in the major groove of DNA. The DNA cleavage experiment was performed by gel electrophoretic assay, indicating that DNA cleavage activity of the complex is concentration dependent and much sensitive to ionic strength. The efficient cleavage mediated via hydrolytically cleaving pathway. Communicated by Ramaswamy H. Sarma

Pentanuclear Spirocyclic Ni4Ln Derivatives: Field Induced Slow Magnetic Relaxation in the Dysprosium and Erbium Analogues

Five pentanuclear heterometallic isostructural complexes, [Ni4Ln(L)2(LH)2(CH3CN)3Cl]·xH2O·yCH3OH {Ln = YIII (1), GdIII (2), TbIII (3), DyIII (4) and ErIII (5)} [for 1 and 2, x = 2, y = 1; for 3, x = 6, y = 2; for 4, x = 5, y = 1; for 5, x = 2, y = 2] were prepared by the reaction of (E)‐2‐(hydroxymethyl)‐6‐{[(2‐hydroxyphenyl)imino]methyl}‐4‐methylphenol (LH3) with LnCl3·6H2O and Ni(OAc)2·4H2O in the presence of tetrabutylammonium hydroxide (TBA‐OH) base. The structural characterization reveals that compounds 1–5 contain a spirocyclic pentanuclear core [Ni4Ln(µ3‐O)4(µ2‐O)4]3+ where two triangular motifs [Ni2Ln(µ3‐O)2(µ2‐O)2]3+ are fused together through a common vertex of the LnIII ion. The central LnIII ion forms an eight‐coordinated distorted triangular dodecahedron geometry, while the nickel(II) ions form a distorted octahedron geometry. Comprehensive dc magnetic studies reveal that antiferromagnetic exchange interaction exists between the NiII centres. The ac susceptibility measurement revels that dysprosium and erbium analogue shows field induced slow magnetic relaxation with an anisotropic barrier (Ueff) of 25.12 cm–1 and 22.13 cm–1 respectively.

Cytotoxic activity of organotin carboxylates based on synthetic phenolic antioxidants and polycyclic bile acids

Two series of organotin(IV) carboxylates based on phenolic antioxidants RCOOH and R(CH2)2COOH (R = 3,5-di-tert-butyl-4-hydroxyphenyl) and natural bile (cholanic) acids of formulae (RCOO)2SnMe2 (1); (RCOO)2SnBu2 (2); (R(CH2)2COO)2SnMe2 (3); (R(CH2)2COO)2SnBu2 (4); (cholate)SnPh3 (5); (deoxycholate)SnPh3 (6); (lithocholate)SnPh3 (7); (cholate)SnMe3 (8); (deoxycholate)SnMe3 (9), and (lithocholate)SnMe3 (10) were synthesized and characterized by 1H, 13C NMR, IR and elemental analysis to study their antioxidant and cytotoxic potential. Compounds 1 and 2 were found by X-ray diffraction analysis to be monomers in the solid state; moreover, the carboxyl groups are coordinated bidentately through O atoms. The distorted octahedron geometry around the Sn center in the monocrystals of 1, 2 was revealed. The antioxidant activity of compounds as radical scavengers and reducing agents was evaluated in spectrophotometrical tests with stable radical DPPH, reduction of Cu2+ (CUPRAC method) and interaction with superoxide anion radical. Cytotoxicity in vitro of compounds has been estimated on human cancer (colon cancer HCT-116, lung carcinoma A549, breast cancer MCF-7, neuroblastoma SH-SY5Y) cell lines and normal fibroblasts cells. The IC50 values varied in 0.002–100 μM range for compounds 1–4 depend on the alkyl substituents at Sn center and carboxylate ligand structure. The influence on Fe3+-induced lipid peroxidation, mitochondrial potential and mitochondrial permeability and tubulin assembly have been studied for the compounds 1 and 2. It was shown that the complexes 1 and 2 slightly depolarize the mitochondria but don’t influence the calcium-induced mitochondrial permeability transition. Organotin complexes with cholic and deoxycholic acids as ligands were revealed to induce apoptosis in A549 cells. The percentage of apoptotic cells were 27.9 and 27.1% for triphenyltin complexes with cholic and deoxycholic derivatives, respectively.

Two organic–inorganic hybrid Schiff base copper materials: synthesis and their catalytic properties for constructing C–N bonds

Two Schiff base copper complexes: [Cu(H2O)2(HL1)]·2H2O (1) (H3L1 =2-((2,4-dihydroxybenzylidene)amino)acetic acid) and [Cu(L2) (CH3OH)]4 (2) (H2L2 = 3-phenyl-2-(2-hydroxy-5-chlorobenzylideneamino)propane-1-ol), have been simply synthesized and fully characterized. Single crystal X-ray diffraction (SXRD) revealed that 1 consists of one five-coordinated copper atom and one deprotonated Schiff base ligand HL1. The copper atom in 1 showed the distorted tetragonal pyramid geometry, whereas, four copper atoms in 2 were six-coordinated and exhibited the distorted octahedron geometry. Importantly, two Schiff base complexes were further used as catalysts in Chan–Lam coupling reaction and 2 demonstrated excellent catalytic performance in construction of C–N bonds (yields up to 87%).

Synthesis, spectral characterization, molecular docking studies, biological activity of (E)-2-((E)-3-(3,4,5-trimethoxyphenyl)allylidene) and (E)-N-phenyl 2-((E)-3-(3,4,5-trimethoxyphenyl)allylidene)hydrazinecarbothioamides and their Cu(II) complexes

Two slightly distorted octahedral complexes of copper(II) with (E)-2-((E)-3-(3,4,5-trimethoxyphenyl)allylidene)hydrazinecarbothioamide (L1) common name 3,4,5-trimethoxy-cinnamaldehydethiosemicarbazone and (E)-N-phenyl-2-((E)-3-(3,4,5-trimethoxyphenyl)-allylidene)hydrazinecarbothioamide (L2) common name 3,4,5-trimethoxycinnamaldehyde-4-phenylthiosemicarbazone have been synthesized. The two free ligands and their copper(II) complexes were characterized by spectroscopic techniques like FT-IR, FT-Raman, UV, EPR, Powder X-ray diffraction and cyclic voltammetry. The EPR spectra evidenced a rhombically distorted octahedron geometry for both the copper(II) complexes. The band gap calculations for the ligands L1, L2 and their complexes Cu(L1)2Cl2 and Cu(L2)2Cl2 were found to be 2.98, 2.61, 2.66 and 2.50 eV respectively. Cu(L1)2Cl2 and Cu(L2)2Cl2 have shown 50% of viability at 80 μg/ml and 60 μg/ml. The anti-oxidant activity study revealed that the compounds are good reductants of DPPH radical. Moderate to good anti-bacterial activity is shown by the compounds against the Gram-positive and Gram-negative bacteria. Molecular docking studies have been carried out to predict the orientation and binding mode of analysis in the active site. The synthesized ligand and complex well occupy (catalytic triad and adenine-binding site) in the active site of β-ketoacyl-acyl carrier protein synthase III enzyme, and also well occupy in helix 11 (in the DCS complex) of human estrogen receptor. Moreover they form water mediated hydrogen bond and hydrogen bond with Cys530 residue.

Crystal structure and thermal properties of bis-[μ-2-(meth-oxy-carbonyl-hydrazinyl-idene)acetato-κ3 N 1,O:O]bis-[di-aqua-(thio-cyanato-κN)manganese(II)] tetra-hydrate.

The title compound, [Mn2(C4H5N2O4)2(NCS)2(H2O)4]·4H2O (I), exists as a centrosymmetric dimer. Each dimeric unit consists of tridentate (O,O,N)-chelating Schiff bases with symmetry-maintained μ-O-bridged carboxyl-ate anions, terminally bound thio-cyanate anions, and ligated and solvated water mol-ecules. The complex exhibits a distorted octa-hedron geometry and the centrosymmetric μ-O-bridged carboxyl-ate anions connect the two manganese atoms to form an M 2O2 ring. In the crystal, the mol-ecules are inter-linked via strong N-H⋯O and O-H⋯O hydrogen-bonding contacts and weak O-H⋯S inter-molecular inter-actions, forming a three-dimensional mol-ecular network.

First Mononuclear Lanthanide Imidazolium Carboxylates

The synthesis and structural analysis of six new lanthanide imidazolium carboxylates are discussed. The first mononuclear lanthanide imidazolium carboxylate salts, [{(L)2M}3+{NO3−}3], M=Sm (1), Gd (2), Dy (3) and Y (4), were synthesized from the reaction between zwitterionic tris-imidazolium carboxylate and corresponding metal nitrate salts. The presence of monodentately coordinating carboxylate groups in 1–4 are confirmed by FT-IR spectra. The isostructural salts 1–4 are discrete tricationic monomer. To the best of our knowledge, the ionic salts 1–4 are the first structurally characterized mononuclear lanthanide imidazole carboxylates. The coordination environment of M(III) is fulfilled by six carboxylate oxygen atoms of ligands in distorted octahedron geometry.

A new supramolecular chromium(III) complex: Synthesis, structural determination, optical study, magnetic and antibacterial activity

A new chromium (III) complex 1,5-Naphthyridine Trans-diaquadioxalatochromate (III) dihydrate, had been synthesized by self-assembly of chromium (III) nitrate with oxalic acid and 1,5-Naphthyridine. The complex was characterized by X-ray diffraction, Fourier Transform Infrared spectroscopy, thermogravimetric analysis and UV–Visible spectroscopy. The crystal morphology was carried out using Bravais–Friedel–Donnay–Harker (BFDH) model. Single crystal X-Ray structure determination revealed that the complex posses two crystallographically independent Cr(III) centers. Each Cr(III) has a distorted octahedron geometry involving two axial O atoms from two water molecules and four equatorial O atoms from two oxalate dianions forming trans-[Cr(C2O4)2(H2O)2]- complex anions. The charge compensation is accomplished by the incorporation of 1,5-Naphthyridine cations. Connection between these entities is ensured by means of strong hydrogen bonds giving rise to 3D supramolecular architecture. Hirshfeld surface analysis and the related 2D fingerprint plots were used for decoding plausible intermolecular interactions in the crystal packing. The magnetic properties of the complex had been investigated and discussed in the context of its structure. The antimicrobial activity was evaluated by disc diffusion method highlighting an antagonistic effect of the synthesized complex against Gram-positive and Gram-negative species.

Synthesis, spectroscopic and crystal structure of a new 2D coordination polymer of Ni(II) constructed by naphthalene-1,4-dicarboxylic acid; Nanomolar detection of fructose at a nano-structured Ni(II) coordination polymer multiwall carbon nanotube

One new 2D coordination polymer of Ni(II) namely [Ni2(ndc)2(DMSO)4(H2O)] n , where ndc = naphthalene-1,4-dicarboxylic acid and DMSO = dimethyl sulfoxide, has been synthesized and characterized by elemental analysis, spectral (IR, UV–Vis), thermal (TG/DTG) analysis and single-crystal X-ray diffraction. This coordination polymer possesses a 2D layer structure constructed from dinuclear nickel(II) building blocks in which two crystallographically independent Ni2+ ions are bridged by ndc2− ligands and water molecule. The ndc2− ligands adopt μ3 bridging modes, linking the metal centers into a two-dimensional coordination network. The two independent NiII cations are surrounded by dimethyl sulfoxide and naphthalene-1,4-dicarboxylate molecules in a distorted octahedron geometry. In the crystal structures of Ni(II) coordination polymer, there are non-classical hydrogen bonding arrangements and C–H∙∙∙π stacking interactions. Electrochemical behavior of [Ni2(ndc)2(DMSO)4(H2O)] n , (Ni-NDA) on the surface of carbon nanotubes (CNTs)/glassy carbon electrode (GCE) was described. The surface structure of the sensor was characterized by scanning electron microscopy (SEM). Oxidation of fructose on the surface of modified electrode was investigated with cyclic voltammetry and electrochemical impedance spectroscopy (EIS) and the results showed that the Ni-NDA/CNTs film displays excellent electrochemical catalytic activities toward fructose oxidation.

Syntheses, crystal structures, anticancer activities of three reduce Schiff base ligand based transition metal complexes

Three nickel(II) complexes, [Ni2(L1)2(tren)2(H2O)](ClO4)3 (1), [NiL2(tren)2](ClO4)·2.5H2O (2), [NiL2(tren)2]I·1.5H2O·CH3OH (3) based on amino acid reduced Schiff ligands are synthesized and characterized by physico-chemical and spectroscopic methods. The results show that in all complexes, the amino acid ligand is deprotonated and acts as an anionic ligand. In the dinuclear complex 1, each Ni(II) atom has a distorted octahedron geometry while with different coordination environment. However, the complexes 2 and 3 are mononuclear, almost with the same coordination environment. Furthermore, in vitro experiments are carried out, including MTT assay, Annexin V/PI flow cytometry and western blotting, to assess whether the complexes have antitumor effect. And the results show that all the three complexes have moderate anticancer activity towards human hepatic cancer (HepG2), human cervical cancer (HeLa) and human prostate (PC3) cell lines, in a concentration dependent way. The complex 1 exhibit higher cytotoxicity than the other two complexes and can induce human hepatic cancer cell (HepG2) to cell apoptosis by activating caspase 3.

Synthesis and structural characterization of a new tetranuclear Zr complex supported by unsymmetric N2O2 ligand and its catalytic behaviors for ring-opening polymerization of rac-lactide

A Zr complex [Zr4L2(μ3-O)2(μ-OMe)2 (OiPr)6] (1) containing two heterochiral N atoms was synthesized from an unsymmetric N2O2 ligand 2-(((2-pyridylmethyl)(2-hydroxyphenyl)amino)methyl)-4,6-di(tert-butyl)phenol (H2L) and characterized by single crystal X-ray diffraction. The complex 1 is an unusual tetranuclear zirconium complex with two oxo-, two methoxy- and two phenoxy-bridges. The four zirconium atoms are unequivalently coordinated. Two Zr atoms are 7-coordinate in a distorted pentagonal bipyramidal geometry, and another two Zr atoms are 6-coordinate in a distorted octahedron geometry. The ring-opening polymerization of rac-lactide catalyzed by complex 1, gave slightly isotactic enriched polylactide with moderate polydispersities.

Synthesis, Crystal Structure, and DNA-Binding Studies of a Cadmium(II) Complex With Bis(N-benzylbenzimidazol-2-ylmethyl)aniline

A complex of cadmium (II) picrate (pic) with Bis(N-benzylbenzimidazol-2-ylmethyl)aniline (Bebba), with composition [Cd(Bebba)2](pic)2, was synthesized and characterized by elemental analysis, electrical conductivity and IR and UV/Vis spectral measurements. The crystal structure of the cadmium(II) complex has been determined by single-crystal X-ray diffraction. The cadmium(II) cation is bonded to two Bebba ligands through four benzimidazole nitrogen, resulting in a distorted octahedron geometry. The DNA-binding properties of the cadmium(II) complex were investigated by electronic absorption, fluorescence spectra and viscosity measurements. The experimental results suggest that the cadmium(II) complex binds to DNA in an intercalation mode.

Synthesis, structure, computational, antimicrobial and in vitro anticancer studies of copper(II) complexes with N,N,N′,N′-tetrakis(2-hydroxyethyl)ethylenediamine and tris(2-hydroxyethyl)amine

The present work consists of synthesis, structural characterization, spectral, density functional theory (DFT), antimicrobial, and anticancer studies of two copper(II) complexes, [Cu(THEEN)(DNB)](DNB) (1) and [Cu(TEAH3)2](DNB)2 (2). In these complexes, THEEN is N,N,N′,N′-tetrakis(2-hydroxyethyl)ethylenediamine, a tetrapodal ligand, and TEAH3 is tris(2-hydroxyethyl)amine, a tripodal ligand, and the counter-anion is 3,5-dinitrobenzoate (DNB−). X-ray crystallography studies reveal that both complexes have distorted octahedron geometries. DFT studies have been performed to calculate structural parameters, vibrational bands, and energy gaps of frontier orbital (HOMO-LUMO) with B3LYP/6–31G*/LANL2DZ level of theory using DMSO as solvent. The theoretical and crystallographic analyses are consistent. Antimicrobial studies have been performed with new copper(II) complexes against Gram(+) bacteria (Staphylococcus aureus), Gram(−) bacteria (Serratia marcescens, Sphingobium japonicum, and Stenotrophomonas maltophilia) and fungal species (Candida albicans, Aspergillus niger, and Saccharomyces cerevisiae). The copper(II) complexes have also shown in vitro cytotoxicity on MCF-7, HCT-116, and HL-60 human cell lines. This study demonstrates that 2 was active against MCF-7 cell lines with IC50 of 23 μg/mL.

Structure, Characterization and Photocatalytic Activity of a Series of Well-Established Covalent Heterojunction Coordination Polymers

Six novel coordination polymers {Co(HCOO)2(4,4′-bipy)}n (1), {[Ni(4,4′-bipy)(OH)2(H2O)2]·suc·2H2O}n (2), {Ni(HCOO)2(4,4′-bipy)}n (3), {Zn(HCOO)2(4,4′-bipy)}n (4), {Cu(HCOO)2(4,4′-bipy)}n (5) and {[Cu(ox)(2,2′-bipy)]·2H2O}n (6) (suc succinic acid, ox oxalic cid) based on pyridine derivatives and carboxylates as ligands were designed and synthesized. The coordination polymers were characterized by elemental analysis, IR and UV–Vis spectra, powder X-ray diffraction, the thermo gravimetric analyses and single-crystal diffraction analysis. The structure analysis showed that the central metal atoms in coordination polymers 1, 2, 3, 4 and 6 all were six-coordination modes, forming distorted octahedron geometries. Cu atom in the coordination polymer 5 was four-coordination mode, forming square planar coordination geometry. While in the coordination polymers 1, 3 and 4, two metal centers were connected by bridging coordination fashions of formic acid ligand, forming a three-dimensional network structure, and in the coordination polymer 6, the two metal centers were connected by bridging coordination fashions of oxalic acid ligand, forming one-dimensional chain. In addition, the photocatalytic activity of a series of covalent heterojunction coordination polymers was studied.

Mimicing bromoperoxidase for copper complexes: Synthesis, structures and properties of Cu(II)–triazine pyrazolyl complex

Copper complexes [Cu2(μ2-C2O4)(HC2O4)(L1)]·(H2C2O4) (1), [Cu2(Bpz∗T-OEt)2Cl2CuCl4] (Bpz∗T-EtOH=L2) (2) and [Cu2(Bpz∗T-O)4]·4pz∗·4H2O (3) (Bpz∗T-O=L3) (L1=2,4-bis(3,5-dimethyl-1H-pyrazol-1-yl)-6-diethylamino-1,3,5-triazine, Bpz∗T=2,4,6-tri(3,5-dimethylpyrazol-1-yl)-1,3,5-triazine) have been synthesized in the reaction of Cu(Ac)2·2H2O, oxalic acid, L1 (for 1) or Bpz∗T (for 2 and 3) and CuCl2·2H2O with solution methods. They were characterized by elemental analysis, IR, UV–Vis and thermogravimetric analyses (TG), and the single-crystal X-ray diffraction analysis. Structural analysis reveals that center metal Cu atoms in the complexes 1 and 3 are six-coordination modes, forming distorted octahedron geometries with N2, O2 and N6 donors, respectively. While Cu atom in the complex 2 is four-coordination and five-coordination modes, forming tetragonal pyramid and tetrahedron geometry with N3 Cl2 and N6, respectively. The complexes exhibit catalytic bromination activity in a single-pot reaction of the conversion of phenol red to bromophenol blue in a mixed system of H2O–DMF–KBr at the constant temperature of 30±0.5°C with a buffer solution of NaH2PO4–Na2HPO4 (pH 5.8), indicating that they can be considered as a potential functional model of bromoperoxidase.

The enhanced catalytic performance of cobalt catalysts towards butadiene polymerization by introducing a labile donor in a salen ligand

A family of cobalt complexes supported by a tridentate Schiff base ligand with a labile donor (O, S, N) as a pendant arm (Co1-Co12, formulated as CoL2) were synthesized by the treatment of the corresponding ligands with cobalt acetate tetrahydrate. The resultant complexes were well characterized by elemental analysis, FT-IR, magnetic moment as well as EI-MS. The solid-state structures of Co7 and Co12 were determined by X-ray diffraction and both established a distorted octahedron geometry around the cobalt center. The butadiene polymerization capabilities of the 12 complexes were evaluated and compared in representative cases. Diethylaluminum chloride (AlEt2Cl) was found to be the compatible activator resulting in highly active catalysts for producing polybutadiene of 93.8-98.2% cis-1,4 enchainment with negligible 1,2-structure and trans-1,4 units. It appears that a certain degree of lability of the donor is beneficial for high catalytic activity, generally following the order of O > S > N, and the high cis-1,4 selectivity. Moreover, the remarkable thermal stability of these systems has been achieved: the catalytic systems have the ability of conducting a high level of active and selective polymerization, reaching an upper limit of polymerization temperature of about 70 °C. The enhanced catalytic performances were further rationalized by the established diene polymerization mechanism, which could shed light on developing highly selective and reactive industrially applicable catalysts with an enhanced thermal stability.