title: Synthesis, structure, DNA binding and DNA cleavage activity of oxovanadium(IV) N-salicylidene-S-methyldithiocarbazate complexes of phenanthroline bases.
abstract: Ternary oxovanadium(IV) complexes [VO(salmdtc)(B)] (1-3), where salmdtc is dianionic N-salicylidene-S-methyldithiocarbazate and B is N,N-donor phenanthroline bases like 1,10-phenanthroline (phen, 1), dipyrido[3,2-d:2',3'-f]quinoxaline (dpq, 2) and dipyrido[3,2-a:2',3'-c]phenazine (dppz, 3), are prepared, characterized and their DNA binding and DNA cleavage activity studied. Complex 3 is structurally characterized by single-crystal X-ray crystallography. The molecular structure shows the presence of a vanadyl group in six-coordinate VN(3)O(2)S coordination geometry. The S-methyldithiocarbazate Schiff base acts as a tridentate NSO-donor ligand in a meridional binding mode. The N,N-donor heterocyclic base displays a chelating mode of binding with an N-donor site trans to the vanadyl oxo-group. The complexes show a d-d band in the range of 675-707 nm in DMF. They exhibit an irreversible oxidative cyclic voltammetric response near 0.9 V due to the V(V)/V(IV) couple and a quasi-reversible reductive V(IV)/V(III) redox couple near -1.0 V vs. SCE in DMF-0.1M TBAP. The complexes show good binding propensity to calf thymus DNA giving binding constant values in the range of 7.4 x 10(4)-2.3 x 10(5)M(-1). The thermal denaturation and viscosity binding data suggest DNA surface and/or groove binding nature of the complexes. The complexes show poor chemical nuclease activity in dark in the presence of 3-mercaptopropionic acid (MPA) or hydrogen peroxide. The dpq and dppz complexes show efficient DNA cleavage activity in UV-A light of 365 nm via a type-II mechanistic pathway involving formation of singlet oxygen ((1)O(2)) as the reactive species.
authors.affiliation: Department of Inorganic and Physical Chemistry, Indian Institute of Science, Sir C.V. Raman Avenue, Bangalore 560 012, India.
authors.forename: Pijus K
authors.initials: PK
authors.lastname: Sasmal
authors.forename: Ashis K
authors.initials: AK
authors.lastname: Patra
authors.forename: Akhil R
authors.initials: AR
authors.lastname: Chakravarty
mesh_terms: D001665:Binding Sites; D018360:Crystallography, X-Ray; D004247:DNA / Q000737:chemistry / Q000378:metabolism*; D053837:DNA Cleavage / Q000187:drug effects*; D006834:Hydrazines; D015394:Molecular Structure; D009691:Nucleic Acid Denaturation; D009942:Organometallic Compounds / Q000138:chemical synthesis / Q000737:chemistry; D010084:Oxidation-Reduction; D010618:Phenanthrolines / Q000737:chemistry*; D014638:Vanadates / Q000737:chemistry*; D014783:Viscosity
chemical_list: D006834:Hydrazines; D009942:Organometallic Compounds; D010618:Phenanthrolines; D014638:Vanadates; C016573:methyldithiocarbazate; D004247:DNA; C427203:calf thymus DNA