Metal-assisted red light-induced DNA cleavage by ternary L-methionine copper(II) complexes of planar heterocyclic bases

Ashis K. Patra, Shanta Dhar, Munirathinam Nethaji, Akhil R. Chakravarty

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105 Scopus citations


Ternary copper(II) complexes [Cu(L-met)B(Solv)](ClO4) (1-4), where B is a N,N-donor heterocyclic base like 2,2′-bipyridine (bpy, 1), 1,10-phenanthroline (phen, 2), dipyrido[3,2-d:2′,3′-f]quinoxaline (dpq, 3) and dipyrido[3,2-a:2′,3′-c]phenazene (dppz, 4), are prepared and their DNA binding and photo-induced DNA cleavage activity studied (L-Hmet = L-methionine). Complex 2, structurally characterized by X-ray crystallography, 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 molecule 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) ≫ 1 (bpy). Control cleavage experiments 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) irradiation via a mechanistic pathway involving formation of singlet oxygen as the reactive species. The DNA cleavage activity of the dpq complex 3 is found to be significantly more than its dppz and phen analogues.

Original languageEnglish (US)
Pages (from-to)896-902
Number of pages7
JournalDalton Transactions
Issue number5
StatePublished - Mar 7 2005
Externally publishedYes


ASJC Scopus subject areas

  • Inorganic Chemistry

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