Mohammad Shakir

Divalent, cobalt, nickel, copper and zinc complexes of tetraaza macrocycles bearing polyamide groups: Synthesis and characterization

Abstract A new series of 14–20 membered tetraamide macrocyclic complexes, [ML 1 ]Cl 2 –[ML 8 ]Cl 2 , of cobalt(II), nickel(II), copper(II) and zinc(II) have been prepared via the template condensation of dicarboxylic acid with primary diamines. All the complexes are soluble in most polar solvents. The complexes have been characterized by IR, 1 H NMR, mass, ESR and electronic spectral studies and magnetic measurements. A square planar geometry for the complexes, [ML n ] 2+ , where M = Ni II and Cu II , or a tetrahedral geometry for M = Co II and Zn II have been assigned. The electrical conductivity data in DMSO are as expected for 1:2 electrolytes.

Synthesis, spectroscopic and electrochemical studies of N,N-bis[(E)-2-thienylmethylidene]-1,8-naphthalenediamine and its Cu(II) complex: DNA cleavage and generation of superoxide anion

A novel tetradentate Cu(II) complex of the type, [CuL](NO(3))(2) was synthesized by the interaction of Schiff base ligand, N,N-bis[(E)-2-thienylmethylidene]-1,8-naphthalenediamine, L obtained by the condensation of thiophene-2-carboxaldehyde and 1,8-diaminonaphthalene. The formation of Schiff base ligand, L and its Cu(II) complex was confirmed on the basis of results of elemental analyses, mass, FT-IR, (1)H and (13)C{(1)H} NMR spectral studies. UV-Vis, EPR and magnetic susceptibility data support a square planar environment around Cu(II) ion. However, molar conductance values confirmed 1:2 electrolytic nature for the Cu(II) complex. The electrochemical studies of Cu(II) complex was carried out by using cyclic voltammetry which revealed the complex to exhibit quasi reversible process. The biological activity of Cu(II) complex such as ability to bind DNA and DNA cleavage were studied where the Cu(II) complex was shown to cause considerable DNA cleavage and also generated reactive oxygen species such as superoxide anion. Since it is known that various anticancer drugs act through induction of oxidative stress that is mediated by reactive oxygen species, our results suggest a putative role of Cu(II) complex similar to various anticancer drugs.

Binuclear N6 22-membered macrocyclic transition metal complexes: synthesis and characterization

Abstract A novel family of tetraiminehexaazamacrocyclic complexes [M 2 LX 4 ] (M = Co II , Ni II and Zn II ) and [Cu 2 LX 2 ] 2+ (X = Cl or NO 3 ) has been prepared by the condensation reaction of diethylenetriamine with phthalaldehyde in the presence of metal ions as templates in methanol medium. The complexes have been characterized on the basis of elemental analysis, IR, 1 H NMR, EPR and UV-vis spectroscopic studies, as well as conductivity and magnetic susceptibility data. All the complexes except that of copper, which is square planar, have octahedral structures.

Synthesis and spectral studies of binuclear transition metal complexes of diamidediimine hexaazamacrocycles

Abstract The template condensation of alkylacetoacetate with diethylenetriamine resulted in the formation of homodinuclear transition metal complexes of a 20-membered macrocyclic ligand. The overall geometry and the mode of bonding have been inferred with IR, 1 H NMR, EPR and electronic spectra studies as well as magnetic and molar conductance data. An octahedral geometry around the metal ion is suggested for [M 2 L 1 X 2 ] and [M 2 L′ 1 X 2 ] where M = iron(II) and cobalt(II), and X = Cl or NO 3 . A distorted square planar and a tetrahedron geometry is proposed for [M 2 L 2 ]X 2 and [M 2 L′ 2 ]X 2 when M = copper(II0 and zinc(II) respectively; X = Cl or NO 3 . The distortion in the copper complexes is confirmed through EPR investigation.

Transition metal complexes of 20–22-membered octaazamacrocycles: Synthesis and characterization

Abstract A series of binuclear octaazamacrocyclic complexes [M 2 L 1 X 4 ]-[M 2 L 2 X 4 ] (M  Ni II , Co II and Zn II ; X  Cl or NO 3 ) and [Cu 2 L 1 ]X 4 -[Cu 2 L 2 ]X 4 (X  Cl or NO 3 ) have been synthesized by template condensation reaction of aliphatic primary diamines with 3,6-dimethyl-4,5-diazaocta-3,5-diene-2,7-dione in methanol. The overall geometry and stereochemistry of these complexes have been elucidated by IR, 1 H NMR, EPR and electronic spectral studies, and magnetic susceptibility and conductance values. An octahedral geometry around the metal ion is suggested for nickel, cobalt and zinc complexes, whilst a square planar geometry is proposed for copper complexes.

TEMPLATE SYNTHESIS OF IRON(II), COBALT(II), COPPER(II) AND ZINC(II) COMPLEXES OF DIAMIDEDIIMINE MACROCYCLES

A series of iron(II), cobalt(II), copper(II) and zinc(II) complexes containing tetraazamacrocyclic ligands have been prepared by the condensation of 1,2-diaminoethane, 1,3-diaminopropane and ortho-phenylene diamine with methyl acetoacetate or ethyl acetoacetate in the presence of iron(II), cobalt(II), copper(II) and zinc(II) salts at room temperature. The structure and bonding of macrocyclic ligands have been studied from elemental analysis, magnetic susceptibility measurements, IR, 1H NMR, mass, EPR and electronic spectra of the complexes. The stereochemistry around the metal ions is octahedral in which four of the coordination sites are occupied by the nitrogens of the macrocyclic ligand and the remaining octahedral positions are occupied by two chlorines.

A new synthetic route for the preparation of a new series of 14–22-membered tetraoxomacrocyclic tetraamines and their transition metal complexes

Abstract The condensation of aliphatic diamines H 2 N(CH 2 ) n NH 2 ( n = 2–3) with dicarboxylic acids in the presence of DCC (dicyclohexylcarbodiimide) and DMAP [4-(dimethylamino)pyridine] gave new types of 14–22-membered tetraamide macrocyclic ligands L 1 L 10 which were characterized by element analysis and mass, IR and 1 H NMR spectroscopic techniques. The complexes of these macrocyclic moieties with some transition metal ions have also been synthesized. The mode of bonding and overall geometry of these complexes has been inferred through UV-vis, IR, 1 H NMR and ESR spectral techniques as well as molar conductance and magnetic moment data. An octahedral geometry around the metal ion is suggested for [ML 1 Cl 2 ]-[ML 10 Cl 2 ], where M = Mn II , Fe II and Co II , while a square planar, a distorted tetrahedral and a tetrahedral geometry is proposed for [ML 1 ]Cl 2 -[ML 10 ]Cl 2 for M = Ni II , Cu II and Zn II , respectively. Bonding parameters have been derived from the ESR hyperfine structure of copper and cobalt complexes.

Six-coordinate dinuclear hexaazamacrocyclic complexes of nickel(II), copper(II) and zinc(II) with tetraamide group ligands

SummaryA series of 20–24 membered macrocyclic dinuclear transition metal complexes [M2L1X4]-[M2L4X4] (M = NiII, CuII or ZnII; X = Cl or NO3) have been synthesized by template condensation of diethylenetriamine with dicarboxylic acids. The bonding and stereochemistry of the complexes have been characterized by i.r.,1H-n.m.r., e.p.r. and electronic spectral studies, magnetic susceptibility and conductivity measurements. The Ni and Zn complexes exhibit octahedral geometry around the metal ion, whereas the Cu complexes possess a distorted octahedral geometry. Each metal ion is coordinated by two amide nitrogens and two secondary nitrogens of the diethylenetriamine moiety; the fifth and sixth coordination sites are occupied by the anions.

Synthesis and structural characterization of cobalt(II), nickel(II) and copper(II) complexes of 18-membered mixed-donor macrocycles

Abstract A series of 18-membered mixed nitrogen, oxygen and sulphur donor atom-containing macrocyclic complexes [ML 2 ]X 2 -[ML 2 ]X 2 (M = Co 11 , Ni 11 and Cu 11 ; X = Cl, Br or NO 3 ) have been synthesized by the template condensation reaction of 2,5-diformylfuran, β-mercaptoethylamine or o -aminothiophenol and 1,3-dibromopropane in ethanol medium and have been characterized through IR, 1 H NMR, EPR and electronic spectral studies, conductivity and magnetic susceptibility measurements. An octahedral geometry has been suggested for the cobalt complexes while square planar and five-coordinate square pyramidal geometry is proposed for the nickel and copper complexes, respectively.

Nano-hydroxyapatite/chitosan-starch nanocomposite as a novel bone construct: Synthesis and in vitro studies.

A novel ternary nanocomposite system incorporating hydroxyapatite, chitosan and starch (n-HA/CS-ST) has been synthesized by co-precipitation method at room temperature, addressing the issues of biocompatibility, mechanical strength and cytotoxicity required for bone tissue engineering. The interactions, crystallite size, surface morphology and thermal stability against n-HA/CS nanocomposite have been obtained by comparing the results of FTIR, SEM, TEM, DLS, XRD and TGA/DTA. A comparative study of bioactivity and thermal stability of n-HA/CS and n-HA/CS-ST nanocomposites revealed that the incorporation of starch as templating agent enhanced these properties in n-HA/CS-ST nanocomposite. A lower swelling rate of n-HA/CS-ST relative to n-HA/CS indicates a higher mechanical strength supportive of bone tissue ingrowths. The MTT assay on murine fibroblast L929 and human osteoblasts-like MG-63 cells and in vitro bioactivity of n-HA/CS-ST matrix referred superior non-toxic nature of n-HA/CS-ST nanocomposite and greater possibility of osteointegration in vivo respectively. Furthermore n-HA/CS-ST exhibited improved antibacterial property against both Gram-positive and Gram-negative bacteria relative to n-HA/CS.