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Papers by Vengidusamy Narayanan

Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy, 2010

A series of N-benzoylated cyclam ligands incorporating three different benzoyl groups 1,4,8,11-te... more A series of N-benzoylated cyclam ligands incorporating three different benzoyl groups 1,4,8,11-tetra-(benzoyl)-1,4,8,11-tetraazacyclotetradecane (L 1 ), 1,4,8,11-tetra-(2-nitrobenzoyl)-1,4,8,11tetraazacyclotetradecane (L 2 ) and 1,4,8,11-tetra-(4-nitrobenzoyl)-1,4,8,11-tetraazacyclotetradecane (L 3 ) and their nickel(II) and copper(II) complexes are described. Crystal structure of L 1 is also reported. The ligands and complexes were characterized by elemental analysis, electronic, IR, 1 H NMR and 13 C NMR spectral studies. N-benzoylation causes red shift in the max values of the complexes. The cyclic voltammogram of the complexes of ligand L 1 show one-electron, quasi-reversible reduction wave in the region −1.00 to −1.04 V, whereas that of L 2 and L 3 show two quasi-reversible reduction peaks. Nickel complexes show one-electron quasi-reversible oxidation wave at a positive potential in the range +1.05 to +1.15 V. The ESR spectra of the mononuclear copper(II) complexes show four lines, characteristic of square-planar geometry with nuclear hyperfine spin 3/2. All copper(II) complexes show a normal room temperature magnetic moment values eff 1.70-1.73 BM which is close to the spin-only value of 1.73 BM. Kinetic studies on the oxidation of pyrocatechol to o-quinone using the copper(II) complexes as catalysts and hydrolysis of 4-nitrophenylphosphate using the copper(II) and nickel(II) complexes as catalysts were carried out. All the ligands and their complexes were also screened for antimicrobial activity against Gram-positive, Gram-negative bacteria and human pathogenic fungi. .in (V. Narayanan). parent macrocycles . Understanding of N-substitution of the ligand on coordination remains an important field of research. Copper catalyzed oxidation of phenols and hydrolysis of the active sites in a number of enzymes by nickel ions [18] are important chemical processes in biological systems.

Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy, 2010

A series of N-benzoylated cyclam ligands incorporating three different benzoyl groups 1,4,8,11-te... more A series of N-benzoylated cyclam ligands incorporating three different benzoyl groups 1,4,8,11-tetra-(benzoyl)-1,4,8,11-tetraazacyclotetradecane (L 1 ), 1,4,8,11-tetra-(2-nitrobenzoyl)-1,4,8,11tetraazacyclotetradecane (L 2 ) and 1,4,8,11-tetra-(4-nitrobenzoyl)-1,4,8,11-tetraazacyclotetradecane (L 3 ) and their nickel(II) and copper(II) complexes are described. Crystal structure of L 1 is also reported. The ligands and complexes were characterized by elemental analysis, electronic, IR, 1 H NMR and 13 C NMR spectral studies. N-benzoylation causes red shift in the max values of the complexes. The cyclic voltammogram of the complexes of ligand L 1 show one-electron, quasi-reversible reduction wave in the region −1.00 to −1.04 V, whereas that of L 2 and L 3 show two quasi-reversible reduction peaks. Nickel complexes show one-electron quasi-reversible oxidation wave at a positive potential in the range +1.05 to +1.15 V. The ESR spectra of the mononuclear copper(II) complexes show four lines, characteristic of square-planar geometry with nuclear hyperfine spin 3/2. All copper(II) complexes show a normal room temperature magnetic moment values eff 1.70-1.73 BM which is close to the spin-only value of 1.73 BM. Kinetic studies on the oxidation of pyrocatechol to o-quinone using the copper(II) complexes as catalysts and hydrolysis of 4-nitrophenylphosphate using the copper(II) and nickel(II) complexes as catalysts were carried out. All the ligands and their complexes were also screened for antimicrobial activity against Gram-positive, Gram-negative bacteria and human pathogenic fungi. .in (V. Narayanan). parent macrocycles . Understanding of N-substitution of the ligand on coordination remains an important field of research. Copper catalyzed oxidation of phenols and hydrolysis of the active sites in a number of enzymes by nickel ions [18] are important chemical processes in biological systems.