Dhar, S.; Nethaji, M.; Chakravarty, A. R. Synthesis, crystal structure and photo-induced DNA cleavage activity of ternary copper(II) complexes of NSO-donor Schiff bases and NN-donor heterocyclic ligands.
Inorganica Chimica Acta 2005,
358, 2437-2444.
Abstract
New ternary Cu(II) complexes [CuLnB](ClO4) (1-3), where HLn is the NSO donor Schiff base derived from the condensation of 2-mercaptoethylamine hydrochloride with salicylaldehyde (HL1) or 2-hydroxy-3-methoxybenzaldehyde (HL2) and B is NN-donor heterocyclic base like 2,2'-bipyridine (bpy, 1), 1,10-phenanthroline (phen, 2) or 2,9-dimethyl-1,10-phenanthroline (dmp, 3), were prepd., structurally characterized by x-ray crystallog. and their DNA cleavage activity studied. The complexes show distorted square-pyramidal (4 + 1) CuN3OS coordination geometry in which the NSO-donor Schiff base is bonded at the basal plane and the NN-donor heterocyclic base displays axial-equatorial mode of bonding [Cu-S distance: ∼2.4 Å]. The 1-electron paramagnetic (μeff .simeq.1.9 μB) complexes display axial EPR spectra in DMF glass at 77 K giving g.dblvert. .simeq.2.2 (A.dblvert. = 162 G) and g.perp. .simeq.2.0, indicating {dx2-y2}1a ground state. The complexes exhibit visible spectral d-d band in MeCN near 650 nm and two charge transfer bands near 400 nm. Complexes 1 and 2 display quasireversible cyclic voltammetric response in DMF-Tris buffer (1:4 vol./vol., pH 7.2) for the Cu(II)/Cu(I) couple at ∼-0.1 V vs. SCE complex 3 exhibits an irreversible redn. process forming [CuI(dmp)2]+. Binding of 1-3 to calf thymus DNA shows the relative order: 2 (phen) ≥ 3 (dmp) > 1 (bpy). Complex 2 efficiently cleaves supercoiled pUC19 DNA in the presence of mercaptopropionic acid (MPA) forming hydroxyl radical or on irradn. with light of 312, 532 and 632.8 nm wavelength in a type-II process. Complexes 1 and 3 are cleavage inactive. [on SciFinder(R)]