DNA Binding and Anti-Cancer Activity of Redox-Active Heteroleptic Piano-Stool Ru(II), Rh(III), and Ir(III) Complexes Containing 4‑(2-Methoxypyridyl)phenyldipyrromethene

The
synthesis of four novel heteroleptic dipyrrinato complexes [(η6-arene)­RuCl­(2-pcdpm)] (η6-arene = C6H6, 1; C10H14, 2) and [(η5-C5Me5)­MCl­(2-pcdpm)]
(M = Rh, 3; Ir, 4) containing a new chelating
ligand 4-(2-methoxypyridyl)-phenyldipyrromethene (2-pcdpm) have been
described. The complexes 1–4 have
been fully characterized by various physicochemical techniques, namely,
elemental analyses, spectral (ESI-MS, IR, 1H, 13C NMR, UV/vis) and electrochemical studies (cyclic voltammetry (CV)
and differential pulse voltammetry (DPV)). Structures of 3 and 4 have been determined crystallographically. In
vitro antiproliferative and cytotoxic activity of these complexes
has been evaluated by trypan blue exclusion assay, cell morphology,
apoptosis, acridine orange/ethidium bromide (AO/EtBr) fluorescence
staining, and DNA fragmentation assay in Dalton lymphoma (DL) cell
lines. Interaction of 1–4 with calf
thymus DNA (CT DNA) has also been supported by absorption titration
and electrochemical studies. Our results suggest that in vitro antitumor
activity of 1–4 lies in the order 2 > 1 > 4 > 3.