Mohd. Khalid

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.

Ammonia vapor sensing properties of polyaniline–titanium(IV)phosphate cation exchange nanocomposite

In this study, the electrically conducting polyaniline-titanium(IV)phosphate (PANI-TiP) cation exchange nanocomposite was synthesized by sol-gel method. The cation exchange nanocomposite based sensor for detection of ammonia vapors was developed at room temperature. It was revealed that the sensor showed good reversible response towards ammonia vapors ranging from 3 to 6%. It was found that the sensor with p-toluene sulphonic acid (p-TSA) doped exhibited higher sensing response than hydrochloric acid doped. This sensor has detection limit ≤1% ammonia. The response of resistivity changes of the cation exchange nanocomposite on exposure to different concentrations of ammonia vapors shows its utility as a sensing material. These studies suggest that the cation exchange nanocomposite could be a good material for ammonia sensor at room temperature.

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.

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.

Isolation of proton transfer complexes containing 4-picolinium as cation and pyridine-2,6-dicarboxylate complex as anion: crystallographic and spectral investigations, antioxidant activities and molecular docking studies

Three novel complexes with stoichiometry [4-pic-H][M(pda)2]·2H2O [M = Cr (1), Fe (2) and Co (3); H2pda = pyridine-2,6-dicarboxylic acid and 4-pic = 4-picoline] have been prepared. The complexes (1–3) are characterized using elemental analysis, TGA, CV, FTIR, ESI mass, 1H & 13C NMR, EPR, UV Visible, fluorescence, magnetic and X-ray studies. Spectral data ascertained the bonding modes and the geometry of the complexes. Single crystal X-ray data of (2) and (3) revealed the formation of proton transfer complexes in which a proton is transferred from the H2pda moiety to the pyridine nitrogen of 4-pic. Thermal and ESI mass data confirmed the proposed stoichiometry of the complexes. Cyclic voltammetric (CV) studies confirm the formation of MII/MIII quasi-reversible redox couples in solution. The antioxidant activity of (3) assessed using DPPH and hydrogen peroxide assays has suggested that the present compounds may be used as potent antioxidants. Molecular docking studies performed for (2) and (3) reveal that the present complexes can efficiently bind with DNA receptor with free energy of binding (FEB) values of −314 (2) and −276.8 kcal mol−1 (3). The molecular docking studies indicated a higher binding ability of (2) to DNA compared to that of (3).

Spectral, thermal and electrochemical characterization of novel homo-dinuclear complexes [M2(H3DTPA)(H2O)6]Cl2·xH2O (M=Cr2+, Mn2+, Co2+, Ni2+ or Cu2+).

The title complexes were prepared and characterized employing spectral (FAB-Mass, IR, electronic, (1)H and (13)C NMR), thermal and electrochemical techniques. Analytical and FAB-Mass data suggested a homo-dinuclear stoichiometry. IR and electronic ligand field spectral studies coupled with molecular model computations have indicated a distorted octahedral geometry where the ligand coordinates as a hexadentate dianionic [H(3)DTPA](2-)(H(5)DTPA=diethylenetriaminepentaacetic acid) moiety. The electrochemical redox properties and the antibacterial activities of the compounds were also investigated.

Novel homo-bimetallic complexes of [N10] macrocyclic ligand modified with tetrapeptide function: Biological activities, spectral and cyclic voltammetric studies

The bimetallic complexes [M(2)LCl(4)] (M=Cr, Co, Ni, Cu) prepared via metal template cyclization reactions were characterized by physico-chemical and spectroscopic methods. L is a 30-membered [N(10)] macrocycle with tetraamide functions bind metal ions through aza donors forming hexa-coordinate geometry. The perspective view and important structural parameters have been computed from the molecular model (MOPAC) method. The electrochemical studies indicate existence of quasi-reversible redox couples in solution. The metal complexes were screened (in vitro) against a few pathogenic fungi and bacteria to assess their growth inhibiting potential.

Synthesis and spectral investigations of mononuclear [N6], [N8] and dinuclear [N10] complexes of polyamide macrocycles: 57Fe Mössbauer parameters of Fe(III) complexes

New stable Fe(III) complexes of tetraamide [N(6)], [N(8)] and [N(10)] macrocyclic ligands are reported. One of them, [N(10)] is dinucleating, with two Fe(III) nuclei in the macrocyclic cavities. The structural features have been discussed on the basis of analytical, ESI mass, FT-IR, electronic, (1)H and (13)C NMR spectral studies. Magnetic moment studies indicate presence of anti-ferromagnetically coupled (Fe(3+)-Fe(3+)=S(5/2)-S(5/2)) spin-spin interactions in the dinuclear [N(10)] complex. (57)Fe Mössbauer measurements confirm Fe(+/-3/2-->+/-1/2) nuclear transitions supporting high-spin configuration of Fe(III) nuclei with the presence of Kramers double degeneracy.

Syntheses, crystal structures, and genotoxic studies of cis-µ-1,2-peroxo dicobalt(III) complexes

Two peroxo-bridged dinuclear Co(III) complexes, {[Co2(ea)2(Phen)2(O2)]·5.5H2O·2Cl} (1) and {[Co2(ea)2(Bipy)2(O2)]·2H2O·2NO3} (2) (Hea = ethanolamine, Phen = 1,10-phenanthroline, Bipy = 2,2′-bipyridine), are prepared by reaction of CoCl2·6H2O or Co(NO3)2·6H2O with Hea in the presence of an α-diimine (Phen or Bipy) under reflux. The complexes have been characterized by IR, NMR, thermal gravimetric analysis, cyclic voltammetric (CV), powder X-ray diffraction, and single-crystal XRD techniques. Single-crystal X-ray crystallographic investigations of 1 and 2 reveal that each Co(III) is coordinated by one deprotonated ethanolamine and an α-diimine chelate. The remaining coordination sites of the metal ions are satisfied by bridging peroxide (O22−) in a cis-μ-1,2 manner. The distances [O–O = 1.487(6) (1) and 1.462(3) Å (2) and Co⋯Co = 2.731(12) (1) and 2.7426(6) Å (2)] support the peroxo bridging in a cis manner in both complexes. The crystal lattice is consolidated via extensive H-bonding and π‒π interactions to form a 3-D supramolecular architecture. Thermal data are consistent with the proposed stoichiometry and presence of lattice water. The CV studies of 1 indicate the presence of a quasi-reversible redox couple (CoIII‒CoIII/CoII‒CoII) in solution. Genotoxic studies are also performed on 1 to investigate the possible applications and side effects of the compounds in medicine. The present work describes syntheses and X-ray studies of two unusual cis-peroxo bridged dinuclear Co(III) complexes. The genotoxic studies performed on the complex reveal that the complex can be exploited for industrial applications at low concentration.