Patra, A. K.; Dhar, S.; Nethaji, M.; Chakravarty, A. R. Metal-assisted red light-induced DNA cleavage by ternary L-methionine copper(ii) complexes of planar heterocyclic bases.
Dalton Transactions 2005, 896-902.
Abstract
Ternary Cu(II) complexes [Cu(L-met)L(Solv)](ClO4) (1-4) (L = a N,N-donor heterocyclic base such as bpy, 1, phen, 2, dipyrido[3,2-d:2',3'-f]quinoxaline (dpq, 3) and dipyrido[3,2-a:2',3'-c]phenazine (dppz, 4)), were prepd. and their DNA binding and photo-induced DNA cleavage activity studied (L-Hmet = L-methionine). Complex 2, structurally characterized by x-ray crystallog., shows a square pyramidal (4 + 1) coordination geometry in which the N,O-donor L-methionine and N,N-donor heterocyclic base bind at the basal plane and a solvent mol. is coordinated at the axial site. The complexes display a d-d band at ∼600 nm in DMF and exhibit a cyclic voltammetric response due to the Cu(II)/Cu(I) couple near -0.1 V in DMF-Tris-HCl buffer. The complexes display significant binding propensity to the calf thymus DNA in the order: 4 (dppz) > 3 (dpq) > 2 (phen) .mchgt. 1 (bpy). Control cleavage expts. using pUC19 supercoiled DNA and distamycin suggest major groove binding for the dppz and minor groove binding for the other complexes. Complexes 2-4 show efficient DNA cleavage activity on UV (365 nm) or red light (632.8 nm) irradn. via a mechanistic pathway involving formation of singlet O as the reactive species. The DNA cleavage activity of the dpq complex 3 is significantly more than its dppz and phen analogs. [on SciFinder(R)]