Bibhesh K. Singh

Spectroscopic characterization and biological activity of Zn(II), Cd(II), Sn(II) and Pb(II) complexes with Schiff base derived from pyrrole-2-carboxaldehyde and 2-amino phenol

A new Schiff base 2-aminophenol-pyrrole-2-carboxaldehyde and its Zn(II), Cd(II), Sn(II) and Pb(II) complexes have been synthesized and characterized by various physicochemical studies. Spectral studies (IR and (1)H NMR) indicate deprotonation and coordination of phenolic oxygen along with binding of pyrrole nitrogen, azomethine nitrogen and anion with metal ions. The presence of lattice water molecule(s) has also been confirmed by TG/DTA studies. Mass spectrum explains the successive degradation of the molecular species in solution and justifies ML complexes. Kinetic and thermodynamic parameters were computed from the thermal data using Coats and Redfern method, which confirm first order kinetics. The bio-efficacy of the ligand and their complexes has been examined against the growth of bacteria in vitro to evaluate their antimicrobial potential. Molecular structures of the complexes have been optimized by MM2 calculations and suggest a tetrahedral geometry around metal ions.

Spectral studies on copper(II) complexes of biologically active glutathione

Copper(II) complexes of reduced glutathione (GSH) of general composition Na[Cu(L)(X)]*nH2O (where LH2=GSH; X=Cl-, NO3-, NCS-, CH3CO2-, HCO2-, ClO4- and n=0-4) have been prepared and characterized by elemental analysis, magnetic susceptibility measurements, IR spectroscopy, EPR spectroscopy and ligand-field spectroscopy. The EPR and ligand field spectra in the solid state suggest planar geometry for all the complexes.

Synthesis, characterization and biological activity of transition metal complexes with Schiff bases derived from 2-nitrobenzaldehyde with glycine and methionine

Schiff bases derived from 2-nitrobenzaldehyde with amino acids (glycine, methionine) and their Co(II), Ni(II) and Cu(II) complexes have been synthesized and characterized by various physico-chemical techniques. From spectral studies, it has been concluded that the ligands acts as bidentate molecule, coordinates metal through azomethine nitrogen and carboxylate oxygen. Mass spectrum explains the successive degradation of the molecular species in solution and justifies ML(2) complexes. X-ray powder diffraction helps to determine the cell parameters of the complexes. Molecular structure of the complexes has been optimized by MM2 calculations and suggests a square planar geometry. The ligands and their metal complexes have been tested in vitro against Streptococcus, Staph, Staphylococcus aureus and Escherchia coli bacteria in order to assess their antibacterial potential. The results indicate that the biological activity increases on complexation.

Spectroscopic characterization of complexes of tetracycline with cobalt(II), nickel(II), cadmium(II) and inorganic Sn(II)

Complexes of Co(II), Ni(II), Cd(II) and inorganic Sn(II) with tetracycline (TC) have been synthesized and characterized by elemental analyses, vibrational spectra, electronic spectra, 1H NMR spectra, magnetic susceptibility measurement, thermal studies and X-ray powder diffraction studies. TC forms a 1:1 complex with the metal ions through the oxygen of the hydroxyl group at the A ring and the carbonyl oxygen atom of the amide group in coordination. The results of spectral techniques and magnetic susceptibility measurement correlate well. Kinetic and thermodynamic parameters were computed from the thermal data using the Coats and Redfern method, which confirm first order kinetics. X-ray powder diffraction data determined the cell parameters of the complexes. The molecular structures of the complexes have been optimized by MM2 calculations and supported square planar/tetrahedral geometry around Metal (II) ions.

Syntheses and characterization of new polydentate amide ligands with inorganic tin (II) and lead (II) ions

Complexes of inorganic Sn(II) and Pb(II) with new ligands N′,N″-bis(3-carboxy-1-oxopropanyl) 2-amino-N-arylbenzamidine (C21H21N3O6) and N′,N″-bis(3-carboxy-1-oxophenelenyl) 2-amino-N-arylbenzamidine (C29H21N3O6) have been synthesized and characterized by elemental analyses, vibrational spectra, electronic spectra, 1H NMR spectra, TOF-mass spectra, thermal studies and X-ray powder diffraction studies. The infrared and 1H NMR spectral data are in agreement with coordination of amide and carboxylate oxygen of the ligands giving a MO4 tetrahedral chromophore. The elemental analyses and mass spectral data are consistent with the formation of ML complexes. Kinetic and thermodynamic parameters were computed from the thermal data using Coats and Redfern method, which confirm first order kinetics. X-ray powder diffraction determines the cell parameters of the complexes. Molecular structures of the complexes have been optimized by MM2 calculations and suggest a tetrahedral geometry around metal (II) ions.

Unsymmetrical Schiff Base Functionalized as Monobasic Tridentate Ligand on Complexation with Some Transition Metal Ions

Cu(II), Co(II), Ni(II) and Mn(II) complexes of Schiff base derived from 2-aminophenol and pyrrole-2- carbaldehyde have been prepared. The complexes are formed by coordination of N and O atoms of the ligand. Their structures were characterized by physico-chemical and spectroscopic methods. Molecular structure of the complexes has been optimized by MM2 calculations and suggests a tetrahedral/ square planar geometry. The bio-efficacy of the ligand and their complexes has been examined against the growth of bacteria in vitro to evaluate their anti-microbial potential.

Spectro-thermal characterization of chromium(III) and manganese(II) complexes with carboxyamide

Complexes of Cr(III) and Mn(II) with N′,N″-bis(3-carboxy-1-oxopropanyl) 2-amino-N-arylbenzamidine (H2L1) and N′,N″-bis(3-carboxy-1-oxophenelenyl) 2-amino-N-arylbenzamidine (H2L2) have been synthesized and characterized by various physico-chemical techniques. The vibrational spectral data are in agreement with coordination of amide and carboxylate oxygen of the ligands with the metal ions. The electronic spectra indicate octahedral geometry around the metal ions, supported by magnetic susceptibility measurements. The thermal behavior of chromium(III) complexes shows that uncoordinated nitrate is removed in the first step, followed by two water molecules and then decomposition of the ligand; manganese(II) complexes show two waters removed in the first step, followed by removal of the ligand in subsequent steps. Kinetic and thermodynamic parameters were computed from the thermal data using Coats and Redfern method, which confirm first order kinetics. The thermal stability of metal complexes has been compared. X-ray powder diffraction determines the cell parameters of the complexes.

Synthesis, characterization and XRPD studies of the bioactive complex of 2-hydroxy-3,5-dimethyl acetophenoneoxime (HDMAOX) with oxovanadium(IV)

The complex of 2-hydroxy-3,5-dimethyl acetophenoneoxime (HDMAOX, HL) with VO(IV) has been synthesized and characterized by different physical techniques. Infrared spectra indicate deprotonation and coordination of the phenolic OH, and nitrogen of the oximino group. Electronic spectra and magnetic susceptibility measurements support square-pyramidal geometry around the metal ion. The elemental analyses and mass spectral data indicate ML2 composition. Thermodynamic activation parameters were computed from the thermal data using the Coats and Redfern method. The crystal data for C20H24N2O5V are: tetragonal, space group P4/m, a = 11.76975 Å, b = 11.76975 Å, c = 18.89209 Å, V = 2617.06 A3, Z = 4. The free ligand (HDMAOX) and its oxovanadium complex have been tested in vitro against Alternaria alternate, Aspergillus flavues, Aspergillus nidulans and Aspergillus niger fungi and Streptococcus, Staph, Staphylococuss and Escherchia coli bacteria in order to assess their antimicrobial potential. The results indicate that the ligand and its metal complex have antimicrobial properties.