Spectroscopic studies of zinc(II)tetraphenylporphyrin molecular complex with 1,4-dioxane

The molecular complex of zinc(II)tetraphenylporphyrin with 1,4-dioxane has been obtained. The IR spectra of the [Zn(TPhP)(1,4-dioxane)2] stabile molecular complex between 4000 and 50cm(-1) have been studied. An interpretation is given on the base the "chair" conformation of 1,4-dioxane molecule.     

Syntheses,crystal structures,electrochemical studies,and antioxidant activities of zinc(II) and copper(II) complexes with bis(2-benzimidazolyl) aniline derivatives

Two ligands, bis(benzimidazol-2-ylmethyl) aniline (bba) and bis(N-methyl-benzimidazol-2-ylmethyl) aniline (Mebba), and their transition metal complexes [Zn(bba)(Br)₂]·2DMF (1) and [Cu(Mebba)(Br)₂]·2DMF (2) have been synthesized and characterized by elemental analyses, molar conductivities, UV–vis spectra, IR spectra, NMR spectroscopy, and X-ray crystallography. The structure around Zn(II) can be described as distorted tetrahedral. Complex 2 can be described as distorted trigonal bipyramidal. Cyclic voltammograms of 2 indicate a quasireversible Cu²⁺/Cu⁺ couple. Additionally, the antioxidant activities of the free ligands and their complexes were determined by the superoxide and hydroxyl radical scavenging methods in vitro. Complexes 1 and 2 possess potent hydroxyl radical scavenging activity and better than standard antioxidants such as vitamin C and mannitol. Complex 2 possesses excellent superoxide radical activity.     

Nickel(II) and zinc(II) complexes of a pyridine ligand bearing a tetrathiafulvalene substituent

The synthesis, crystal structures, and electrochemical properties of the coordination complexes, NiBr₂(ept)₂ and ZnBr₂(ept)₂ (ept?=?4,5-ethylenedioxy-3??-(3??-pyridyl)-tetrathiafulvalene) are reported. Both complexes are mononuclear, with monodentate coordination of the ept ligand through the pyridine nitrogen. Cyclic voltammetry measurements for both complexes show a sizable interaction involving the electroactive ept ligand, with stabilization of the oxidized forms of the complexes.     

Crystal and molecular structure of zinc(II) DI-n-Propyldithiocarbamate complexes with 2,2′-Bipyridyl and 1,10-Phenanthroline

The structure of Zn[S₂CN(n-C₃H₇)₂]₂(2,2′-Bipy) and Zn[S₂CN(n-C₃H₇)₂]₂ Phen was determined by Xray diffraction analysis (CAD-4 diffractometer, MoK_α radiation) for the monoclinic (a = 9.646, b = 20.978, c = 14.555 Å;β = 94.95°; Z = 4; space group P2₁/n) and orthorhombic (a = 18.621, b =14.701, c = 10.676 Å; Z = 4; space group Aba2) crystals. The structures consist of discrete monomer molecules packed with the aid of S…H-C and C…E-C hydrogen bonds and van der Waals interactions.     

Structure and DNA-binding properties of bis(quinolonato)bis(pyridine)zinc(II) complexes

The novel neutral mononuclear zinc complexes with the quinolone antibacterial drugs enrofloxacin and oxolinic acid in the presence of the nitrogen donor heterocyclic ligand pyridine have been synthesized and characterized. The experimental data suggest that the quinolone ligands are on the deprotonated mode acting as bidentate ligands coordinated to the zinc(II) ion through the ketone oxygen and a carboxylato oxygen. The crystal structure of the complex bis(enrofloxacinato)bis(pyridine)zinc(II), 1, has been determined with X-ray crystallography. The biological activity of the complexes has been evaluated by examining their ability to bind to calf-thymus DNA (CT-DNA) with UV and fluorescence spectroscopies. UV spectroscopic titration studies of the interaction of the complexes with DNA have shown that they can bind to CT-DNA and the DNA binding constants have been calculated. Competitive studies with ethidium bromide (EB) have shown that the complexes exhibit the ability to displace the DNA-bound EB indicating that they can bind to DNA in strong competition with EB for the intercalative binding site.     

Chiral zinc(II) and copper(II)-catalyzed asymmetric ring-opening reactions of meso-epoxides with aniline and indole derivatives

The ring-opening reactions of meso-epoxides with aniline and indole derivatives proceeded smoothly in water in the presence of Zn(II) and Cu(II) surfactant-type catalysts to afford the corresponding products in moderate to high yields with good to excellent enantioselectivities. Opposite enantiomers were obtained by using Sc(III) and Zn(II) or Cu(II) with the same chiral ligand. Crystal structures of these catalysts may explain the reversal of the enantioselectivity. Some reactions were also tested in dichloromethane (DCM), and it was revealed that the reactions proceeded faster in water than in DCM. Finally, several non-linear effect experiments suggested unique structure of these chiral catalysts.     

Copper(II) and zinc(II) complexes with terpene derivatives of ethylenediamine: unexpected ligand transformations

Crystallization of copper and zinc complexes with imino terpene derivatives of ethylenediamine causes unexpected chemical transformation of the ligand. Copper(II) chloride catalyzes the hydrolysis of the imine and also acts as a halogenating agent. Crystallization of the zinc complex in acetone is accompanied by the condensation of the ketone with the primary amino group of the ligand.     

A quantum chemical study of the molecular structure of zinc(II) and boron(II) complexes with monoiodo and dibromo substituted dipyrrines

The geometric parameters of the molecular structures of 4-monoiododipyrrine, 4,4′- and 5,5′-dibromodipyrrine complexes with zinc(II) and boron(III) of the composition [ZnL₂] and [BF₂L] respectively are determined at the M06 and B3LYP levels of density functional theory with the Def2-SVP basis set. The lengths of Zn–N, B–N, and B–F coordination bonds, N–X–N, F–B–F, C–C–C bond angles, the dihedral angles between the planes of pyrrole rings in the dipyrrine ligand, dipyrrine planes in [ZnL₂], dipyrrine core and the plane passing through the atoms of the BF₂ group are optimized. The effect of structural factors on the geometric parameters and the widths of the HOMO–LUMO energy gap in halogen substituted dipyrrinates is analyzed.     

Copper(II), cobalt(II), nickel(II) and zinc(II) complexes of Schiff base derived from benzil-2,4-dinitrophenylhydrazone with aniline

New Schiff base chelates of Cu(II), Co(II), Ni(II) and Zn(II) derived from benzil-2,4-dinitro-phenylhydrazone with aniline have been synthesised. Microanalytical data, molar conductance, and magnetic susceptibility values have been obtained, and IR,¹H NMR,¹³C NMR, UV-Vis, CV and EPR spectral studies have been carried out to suggest tentative structures for the complexes     

Crystallographic,spectroscopic and electrochemical characterization of pyridine adducts of magnesium(II) and zinc(II) porphine complexes

A new purification method of magnesium(II) and zinc(II) porphine complexes (MgP and ZnP, respectively) by crystallization of their respective pyridine adducts is described. Pure MgP and ZnP can be regenerated by removal of the coordinated pyridine ligands by heating at 200 °C under vacuum. X-ray crystallographic structures of the pyridine adducts are presented for the first time. NMR analyses of the adducts reveal the coordination of two pyridine molecules. Electrochemical as well as UV-vis absorption spectroscopy analyses in DMF of MgP·(Py)₂, ZnP·(Py)₂, MgP and ZnP indicate that pyridine adducts are totally dissociated. Besides, oxidation peaks of these complexes are totally irreversible, revealing a high reactivity of the oxidized species. Electrolyses at the first oxidation potential lead to the formation of the meso-meso (ZnP)₂ and (MgP)₂ dimers, oligomers and polymers on the electrode surface, as attested by MALDI-TOF mass spectrometry and UV-vis absorption spectroscopy analyses of the crude solution.     

Thermogravimetric investigation of some mononuclear and binuclear complexes of copper(II) acetate with pyridine derivatives

Binuclear complexes of the type Cu₂(CH₃CO₂)₄L₂ (L=pyridine, 2-chloropyridine, 3-chloropyridine, 2,4-dimethylpyridine, 3,4-dimethylpyridine, isoquinoline) and mononuclear complexes of the type Cu(CH₃CO₂)₂Py₃, Cu(CH₃CO₂)₂Py₃H₂O, Cu(CH₃CO₂)₂(3,4-Lut)₂H₂O have been investigated by thermogravimetry. A linear correlation is shown to exist between the pK_a of the base ligand and the thermal stability of the corresponding binuclear complexes as determined from the thermal analysis data. The results show that the tendency to eliminate the base ligand from these complexes decreases with decreasing basicity of the substituted pyridine. The strong steric effect associated with -substituted pyridine ligands on the decomposition temperatures of the corresponding complexes is noted.

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Zusammenfassung Binukleare Komplexe des Typs Cu₂(CH₃CO₂)₄L₂ (L=Pyridin, 2-Chlorpyridin, 3-Chlorpyridin, 2,4-Dimethylpyridin, 3,4-Dimethylpyridin, Isoquinolin) und mononukleare Komplexe des Typs Cu(CH₃CO₂)₂Py₃, Cu(CH₃CO₂)₂Py₃ · H₂O und Cu(CH₃CO₂)₂(3,4-Lut)₂·H₂O werden thermogravimetrisch untersucht. Aus den thermoanalytischen Daten ergibt sich eine lineare Korrelation zwischen denpK _a Wert der basischen Liganden und der thermischen Stabilität der entsprechenden binuklearen Komplexen. Die Tendenz zur Eliminierung der basischen Liganden dieser Komplexe nimmt mit abnehmender Basizität der substituierten Pyridine ab. Auf den beträchtlichen, mit dem-substituierten Pyridinliganden zusammenhängenden sterischen Effekt auf die Zersetzungstemperature der entsprechenden Komplexes wird hingewiesen.

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Cu₂(CH₃CO₂)₄L₂ (L=, 2- 3- , 2,4- 3,4- ), Cu(CH₃COO)₂Py₃, Cu(CH₃COO),Py₃·H₂O Cu(CH₃COO)₂(3,4-)₂ · H₂O. pK _a . , . ga- .

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Presented at the International Summer School of Calorimetry and Thermal Analysis, Belgirate, Italy; October 1–5, 1984.

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The financial support of the Polish Academy of Sciences is gratefully acknowledged. We are also indebted to Dr Pielak for analysing the sintered products.     

Syntheses,molecular structure,and electrochemical investigations of cobalt(II), copper(II), palladium(II), and zinc(II) complexes with 3-methylpyrazole

Mononuclear complexes of 3-methylpyrazole with general formulas (3-Mepz)₄CuCl₂ (1), (3-Mepz)₄CoCl₂ (2), (3-Mepz)₂PdCl₂ (3), and (3-Mepz)₂ZnCl₂ (4) were prepared by reaction of the corresponding MCl₂ salt (M?=?Cu, Co, Pd, and Zn) with 3-methylpyrazole in appropriate amounts using acetonitrile as solvent at ambient temperature. The X-ray crystal structure determination reveals that 1 and 2 possess octahedral geometry, while 3 and 4 are square planar and tetrahedral, respectively. All the synthesized compounds have the MCl₂ fragment, thus making the synthesized compounds attractive synthons for further transformation. The cyclic voltammograms of the synthesized complexes were obtained and the voltammetric signatures of 1, 2, and 4 showed a single irreversible pH-dependent cathodic peak, while 3 has two reversible cathodic peaks. Involvement of protons accompanying the electron transfer processes was ascertained from differential pulse voltammetric results, indicating peak potential shift as a function of pH.     

Copper(II) and zinc(II) complexes with 2-formylpyridine-derived hydrazones

In the present work 2-formylpyridine-para-chloro-phenyl hydrazone (H2FopClPh) and 2-formylpyridine-para-nitro-phenyl hydrazone (H2FopNO₂Ph) were obtained, as well as their copper(II) and zinc(II) complexes [Cu(H2FopClPh)Cl₂] (1), [Cu(2FopNO₂Ph)Cl] (2), [Zn(H2FopClPh)Cl₂] (3) and [Zn(H2FopNO₂Ph)Cl₂] (4). Upon re-crystallization in DMSO:acetone conversion of 2 into [Cu(2FopNO₂Ph)Cl(DMSO)] (2a) and of 4 into [Zn(2FopNO₂Ph)Cl(DMSO)] (4a) occurred. The crystal structures of 1, 2a, 3 and 4a were determined.     

Synthesis,structure and luminescent properties of zinc(II) and Hg(II) complexes with substituted 1,10-phenanthroline

Two d¹⁰ group 12 metal complexes, 2-(2-methoxyphenyl)-1,10-phenanthroline zinc dichloride (2a) and 2-(2-methoxyphenyl)-1,10-phenanthroline mercury dichloride (2b) were synthesized and characterized by IR, ¹H and ¹³C NMR as well as elemental analysis. Structure of 2b in the solid state was determined by single-crystal X-ray crystallography, revealing that 2b is four-coordinate in a distorted tetrahedral geometry with the methoxy group uncoordinated. Luminescent properties of 2a and 2b in solution and the solid state were studied.