title: Reduction of copper(II) complexes of tridentate ligands by nitric oxide and fluorescent detection of NO in methanol and water media.
abstract: Two copper complexes, 1 and 2, with tridentate N-donor ligands, L(1) and L(2) [L(1)= (1-methyl-1H-imidazol-2-ylmethyl)-(2-pyridin-2-yl-ethyl)amine, L(2) = (2-pyridin-2-yl-ethyl)-pyridin-2 yl-methylamine] respectively, have been synthesized and characterized. On exposure to nitric oxide, the copper(II) centers in complexes 1 and 2 were found to undergo reduction in various solvents. In acetonitrile solvent the reduction was accompanied by a simultaneous N-nitrosation on the secondary amine center on the ligand frameworks. Complexes 3 and 4 were prepared with ligands L(3) and L(4), respectively. L(3) and L(4) [L(3) = 5-dimethylamino-naphthalene-1-sulfonic acid (1-methyl-1H-imidazol-2-ylmethyl)-(2-pyridin-2-yl-ethyl)-amide; L(4) = 5-dimethylamino-naphthalene-1-sulfonic acid(2-pyridin-2-yl-ethyl)-pyridin-2-ylmethyl-amide] are the dansyl derivatives of L(1) and L(2), respectively. Complex 4, due to paramagnetic quenching, does not display any fluorescence; however, on addition of nitric oxide to a methanol or water solution of complex 4, the fluorescence intensity of the fluorophore has been found to be restored. This is attributed to the reduction of the Cu(II) center by nitric oxide to diamagnetic Cu(I). The turn-on of quenched fluorescence intensity has been observed both in methanol and water media.
authors.affiliation: Department of Chemistry, Indian Institute of Technology Guwahati, Assam 781039, India.
authors.forename: Pankaj
authors.initials: P
authors.lastname: Kumar
authors.forename: Apurba
authors.initials: A
authors.lastname: Kalita
authors.forename: Biplab
authors.initials: B
authors.lastname: Mondal
mesh_terms: D003300:Copper / Q000737:chemistry*; D005470:Fluorometry / Q000379:methods; D008024:Ligands; D000432:Methanol; D009569:Nitric Oxide / Q000032:analysis / Q000737:chemistry*; D009942:Organometallic Compounds / Q000737:chemistry*; D010084:Oxidation-Reduction; D014867:Water
chemical_list: D008024:Ligands; D009942:Organometallic Compounds; D014867:Water; D009569:Nitric Oxide; D003300:Copper; D000432:Methanol