Zafar A. Siddiqi

Antimicrobial and SOD activities of novel transition metal complexes of pyridine-2,6-dicarboxylic acid containing 4-picoline as auxiliary ligand.

Ternary complexes are potential models for several mono and polynuclear metal enzymes. The present ternary complexes [Fe(dipic)(4-picoline)]Cl, [M(dipic)(4-picoline)] [M = Co or Ni] and [Cu(dipic)(4-picoline)]n were prepared to exploit as novel antimicrobial agents. The chemical structure and bonding etc. were elucidated by spectral studies. Single crystal X-ray data of the Cu(II) complex indicated formation of 1D coordination polymeric structure. The antimicrobial activities investigated against Escherichia coli (K-12), Bacillus subtilis (MTCC-121), Staphylococcus aureus (IOA-SA-22), Salmonella typhymurium (MTCC-98), Candida albicans, Aspergillus fumigatus and Penicillium marneffei (isolates from Department of Microbiology, Faculty of Agricultural Science, AMU) showed significant activities. The superoxide dismutase (SOD) activity of the Cu(II) complex was also assessed by NBT assay.

Antimicrobial and SOD activities of novel transition metal ternary complexes of iminodiacetic acid containing α-diimine as auxiliary ligand

Ternary complexes containing an alpha-diimine auxiliary ligand have been widely used as models for several mono and polynuclear metal enzymes. The present ternary complexes [M(IDA)(Phen)H(2)O] x xH(2)O (x = 2, 3 or 4) were prepared as novel antimicrobial agents employing reactions of Cu(OAc)(2) or MCl(2) (M = Co, Ni, Cr) with iminodiacetic acid (H(2)IDA) in the presence of 1,10-phenanthroline (Phen), whose chemical structure and bonding were elucidated by IR, FAB-Mass, (1)H, (13)C NMR, EPR spectral and elemental analyses. The antimicrobial activities against Escherichia coli (K-12), Bacillus subtilis (MTCC 121), Staphylococcus aureus (IOA-SA-22), Salmonella typhimurium (MTCC 98), Candida albicans, Aspergillus fumigatus and Penicillium marneffei (isolates from Department of Microbiology, Faculty of Agricultural Science, AMU) were investigated and significant activities were obtained. The superoxide dismutase activity of the Cu(II) complex was assessed by NBT assay. The single crystal X-ray structure for [Cu(IDA)(Phen)H(2)O] x 2 H(2)O indicates a triclinic unit cell in P-1 space group with structural parameters, a = 6.745(5), b = 10.551(5), c = 11.414(5)A, alpha = 95.770(5), beta = 91.396(5), gamma = 92.518(5) degrees and presence of an extensive H-bonding and pi-pi stacking interactions which generate a supramolecular framework.

Superoxide scavenging and antimicrobial activities of novel transition metal complexes of oxydiacetate dianion as primary ligand: spectral characterization, cyclic voltammetric investigations and crystal structure.

Complexes of stoichiometries [M(oda)(4-pic)H(2)O]·xH(2)O [M = Cu(1), x = 2; Co (2), x = 4; Ni (3), x = 2; ] [Fe(oda)(4-pic)]·Cl (4) and {[Cu(2-pa)(2)]·2H(2)O}(n) (5) (H(2)oda = oxydiacetic acid, 4-pic = 4-picoline and 2-paH = 2-picolinic acid) were prepared to explore their uses as possible models for mono- and poly-nuclear metallo-pharmaceuticals. The chemical structures were elucidated by IR, FAB-Mass, (1)H, (13)C NMR, EPR and UV-visible (ligand field) spectral analyses. Electrochemical investigations are consistent with formation of stable quasi-reversible redox Co(II/III) and Cu(II/III) couples in the solution. Single crystal X-ray data of the complex (5) indicated a 1D coordination polymeric structure with extensive H-bonding to form supramolecular frameworks. The antimicrobial activities were examined against Escherichia coli (k-12), Bacillus subtilis (MTC-121), Staphylococcus aureus (IOASA-22), Salmonella typhimurium (MTCC-98), Candida albicans, Aspergillus fumigatus and Penicillium marneffei. The superoxide dismutase (SOD) activities of the Cu(II) complexes (1 and 5) were assessed employing nitrobluetetrazolium (NBT) assay.

Transition metal complexes of hydrotris(imidazolyl)borate anion

The preparation and characterization of the ligand potassium hydrotris(imidazolyl)borate and some of its complexes with transition metals is reported. These complexes have apparently an octahedral structure except the Cu(II) complex which seems to have a square planar geometry. The values of the ligand field parameters 10Dq, B and β have been evaluated for most of these complexes.

PREPARATION AND STRUCTURAL CHARACTERIZATION OF 14-16-MEMBERED PENDENT ARM MACROCYCLIC COMPLEXES OF TRANSITION METAL IONS

Abstract Template condensation reaction of ethylenediamine or propylenediamine, formaldehyde and benzidine in 1:2:1 molar ratio in methanol medium resulted in the formation of a new series of pendent arm hexaazamacrocyclic complexes of the type [ML 1 Cl 2 ] or [ML 2 Cl 2 ] (M II = Fe II , Co II , Ni II ,Cu II and Zn II ). These polycrystalline compounds are soluble in DMSO and have been characterized by IR, 1 H NMR, EPR and electronic spectral studies, and conductivity and magnetic susceptibility measurements. An octahedral geometry is suggested for all the complexes, where two coordination sites are occupied by chloride ions and the other four by secondary amines.

An 18-member dinucleating unsymmetrical [N10] macrocycle and its bimetallic complexes M2LCl2(ClO4) (M=Co, Ni, Cu, Zn, Cd or Hg)

The 18-member unsymmetrical dinucleating Shiff-base decaaza [N10] macrocyclic ligand, 2,8,11,17-tetramethyl-3,5,7,12,14,16-hexaphenyl-[1,3,5,7,9,10,12,14,16,18] decaazaoctadeca-2,8,11,17-tetraene dihydroperchlorate (L · 2HClO4) was obtained as a cream colored solid from reaction of N-acetylaniline and hydrazine in the presence of HClO4 followed by cyclization (capping) using aniline and excess HCHO in methanol at RT. Reactions of L · 2HClO4 with MCl2 and [M(Ph3P)2Cl2] afforded air stable complexes, M2LCl4(ClO4)2 (M = Co, Ni, Cu, Zn or Cd). The compounds have been characterized by physico-chemical and spectroscopic studies. FAB–Mass spectral data support bimetallic coordination by the macrocycle. IR studies confirm coordination/encapsulation of metal ions involving unsymmetrical aza sites. Magnetic susceptibility and UV–Visible data indicate a low-spin, five-coordinate geometry for Co(II) and Ni(II) complexes. The anisotropic EPR signals (g ∥ > g ⊥) for Cu2+ complex suggest an axial type tetragonality. Molecular model computations have been employed for a theoretical perspective of the ligand and complexes. The important bond lengths and bond angles have been estimated using CS Chem-3D software. The ionic association constant (K 1) and thermodynamic free energy change (ΔG) were evaluated from the conductometric data of the complexes, which indicate presence of a strong ion-pair even in solution. Cyclic voltametric studies on solutions of M2LCl4(ClO4)2 (M = Co, Ni or Cu) in DMSO indicate reversible and quasi-reversible redox couples.

Structurally well-characterized new multinuclear Cu(II) and Zn(II) clusters: X-ray crystallography, theoretical studies, and applications in catalysis

Two new trinuclear Cu(II) and dinuclear Zn(II) clusters are crystallized out by reacting the metal salts with the triethanolamine (H3tea) ligand in the presence of benzoic acid (Hba). The complexes are characterized by elemental, thermal, magnetic, spectral (FTIR, UV-Visible, EPR, and photoluminescence) and single crystal X-ray studies. Single crystal X-ray crystallography reveals the composition of the complexes to be [Cu3(H2tea)2(ba)2(NO3)2] (1) and [Zn2(H2tea)(ba)3]H2O (2). FTIR ascertains the binding modes of H2tea−, ba− and NO3−. Triethanolamine binds in both the complexes in the monoanionic (H2tea−) mode. ba− is present as an anchoring auxiliary to generate di- and trinuclear clusters. The Cu(II) ion is present as a distorted octahedral center in the Cu3 cluster (1), while the two Zn(II) ions in 2 have been reported for the first time to possess distorted octahedral as well as tetrahedral geometry in the same molecule. The intriguing features of the non-covalent supramolecular interactions have been investigated and supported theoretically by using Hirshfeld surface analysis and ab initio methods. The solid state photoluminescence (PL) spectra of 1 and 2 disclose the luminescence property of the complexes. Due to the closed or nearly closed shell configuration (d9 or d10), the present complexes are screened for catalytic properties in the hydrocarboxylation of alkanes and cycloalkanes. The catalytic activity data are indicative of the potential catalytic properties of 1 and 2.

Spectral studies of Fe(III) complexes of dipodal tridentate chelating agents.

The dipodal ligands (Im) and (BIm) as well as complexes [FeLCl(3)] [L=Im (1) and BIm (2)] have been prepared and studied using spectroscopic techniques. The magnetic moment, IR, electronic (ligand field), FAB-mass and NMR spectral data indicate a hexa-coordinate geometry around high-spin state Fe(3+) where the ligands coordinate as a tridentate [N,N,N] chelating agent. (57)Fe-Mössbauer spectral data confirmed the presence of a ligand asymmetry around Fe(3+) in a high-spin state electronic configuration (t(2g)(3),e(g)(2), S=5/2) with nuclear transition Fe(+/-3/2-->+/-1/2) exhibiting Kramers double degeneracy. The molecular computations provided the optimum energy perspective plots for the molecular geometries giving the important structural data.

Synthesis, vibrational spectra and stereochemistry of lanthanide tris(chlorosulphates), Ln(SO3Cl)3 (Ln = La, Ce, Pr, Nd, Sm, Gd, Tb, Dy, Ho and Er)

Abstract -Lanthanide(III) chlorosulphates, Ln(SO3Cl)3 (Ln = La, Ce, Pr, Nd, Sm, Gd, Tb, Dy, Ho and Er) have been synthesized by solvolytic reaction of chlorosulphuric acid on the corresponding benzoates. The low conductivity values and the IR spectra of these compounds suggest a cation-anion interaction leading to covalent bonding. The bands observed in the reflectance spectra and the values of magnetic moments may indicate a coordination number of 6 for these metals, with bidentate chlorosulphate groups.

Organotellurium Derivatives. Syntheses and Characterization of Dimethyl and Diethyl Telluriumdichlorosulphates [R2Te(SO3Cl)2]

Abstract Dimethyl and diethyl telluriumdichlorosulphates have been isolated in the form of dark brown colored crystalline solids utilizing the solvolytic reactions of the corresponding di-iodides with chlorosulphuric acid. The electrical conductivity and IR spectroscopic studies confirm that these compounds are non-ionic and the mode of linking of the chlorosulphate group to the tellurium atom is covalent, resulting in a reduced Cs symmetry for the chlorosulphate group. The PMR spectral study indicates that the corresponding methyl and ethyl protons of these molecules are deshielded which is consistent with the lowering of the non-bonded electron density at tellurium atom due to its drainage towards the chlorosulphate group.