Synthesis, characterization, crystal structure and antimicrobial activities of new trans N,N-substituted macrocyclic dioxocyclam and their copper(II) and nickel(II) complexes

摘要

New trans-disubstituted macrocyclic ligands, 1,8-[N,N-bis(3-formyl-12- hydroxy-5-methyl)benzyl]-5,12-dioxo-1,4,8,11-tetraazacyclotetradecane (L 1), 1,8-[N,N-bis(3-formyl-12-hydroxy-5-bromo)benzyl]-5,12-dioxo-1,4, 8,11-tetraazacyclotetradecane (L~2), N,N-bis[1,8-dibenzoyl]-5,12- dioxo-1,4,8,11-tetraazacyclotetradecane (L~3), N,N-bis[1,8-(2- nitrobenzoyl)]-5,12-dioxo-1,4,8,11-tetraazacyclotetradecane (L~4), and N,N-bis[1,8-(4-nitrobenzoyl)]-5,12-dioxo-1,4,8,11-tetraazacyclotetradecane (L~5) were synthesized. The ligands were characterized by elemental analysis, FT IR, 1H NMR and mass spectrometry studies. The crystal structure of L~1 is also reported. The copper(II) and nickel(II) complexes of these ligands were prepared and characterized by elemental analysis, FT IR, UV-Vis and mass spectral studies. The cyclic voltammogram of the complexes of ligand L~(1-3) show one-electron quasi-reversible reduction wave in the region -0.65 to -1.13 V, whereas that of L~4 and L~5 show two quasi-reversible reduction peaks. Nickel(II) complexes show one electron quasi-reversible oxidation wave at a positive potential in the range +0.95 to +1.06 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 value μeff 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. The ligands and their complexes were also screened for antimicrobial activity against Gram-positive, Gram-negative bacteria and human pathogenic fungi.