Synthesis, DNA binding, photo-induced DNA cleavage and cell cytotoxicity studies of a family of light rare earth complexes

A family of light rare earth complexes, [RE(acac)(3)(dpq)] (RE = La (1), Ce (2), Pr (3), Nd (4), Sm (5)) and [RE(acac)(3)(dppz)]center dot CH3OH (RE = La (6), Ce (7), Pr (8), Nd (9), Sm (10) viz. acetylacetonate (acac), dipyrido[3,2-d:20,30-f]quinoxaline (dpq), dipyrido[3,2-a:20,30-c] phenazine (dppz)), have been synthesized and structurally characterized. Binding interactions of these complexes with CT-DNA and their photo-induced DNA cleavage activity with pBR 322 DNA are also investigated. These complexes have strong DNA binding interaction (K-b approximate to 10(5) M-1 and K-app approximate to 10(5) M-1) and the binding propensity to CT-DNA decrease with the order: dppz complexes>dpq complexes. Furthermore, DNA photocleavage experiments indicate that these complexes are efficient DNA cleaving agents in UV-A (365 nm) and ambient light in the absence of any external reagents. Hydroxyl radical (HO center dot) and singlet oxygen (O-1(2)) are the major cleavage active species from the machanistic studies. Moreover, cell cytotoxicity studies of these complexes on HeLa. K562 and MDA-MB-231 cells indicate that they have the potential to act as effective metal-based anti-cancer drugs. (C) 2011 Elsevier Inc. All rights reserved.