DNA/Protein Binding, Molecular Docking, and in Vitro Anticancer Activity of Some Thioether-Dipyrrinato Complexes

Syntheses and characterizations of the arene ruthenium [(η⁶-C₆H₆)­RuCl­(4-mtdpm)] (<b>1</b>), [(η⁶-<i>p</i>-MeC₆H₄Prⁱ)­RuCl­(4-mtdpm)] (<b>2</b>), and structurally analogous rhodium/iridium complexes [(η⁵-C₅Me₅)­RhCl­(4-mtdpm)] (<b>3</b>) and [(η⁵-C₅Me₅)­IrCl­(4-mtdpm)] (<b>4</b>) [4-mtdpm = 5-(4-methylthiophenyl)­dipyrromethene] have been reported. Their identities have been established by satisfactory elemental analyses, electrospray ionization-mass spectrometry (ESI-MS), FT-IR, NMR (¹H, ¹³C), UV/vis, emission spectral, and electrochemical studies. Structure of the representative complex <b>3</b> has been authenticated by X-ray single crystal analyses. The complexes <b>1</b>–<b>4</b> effectively bind with calf thymus DNA (CT DNA) through intercalative/electrostatic interactions. In addition, these exhibit significant cytotoxicity toward Dalton lymphoma (DL) cell line and cause static quenching of the bovine serum albumin (BSA) fluorophore. The antiproliferative activity, morphological changes, and apoptosis have been evaluated by MTT assay, acridine orange/ethidium bromide (AO/EtBr) fluorescence staining, and DNA ladder assay. Mode of interaction of the complexes with DNA/protein has also been supported by molecular docking. Various studies revealed remarkable decrease in the in vitro DL cell proliferation and induction of the apoptosis by <b>1</b>–<b>4</b>, which lies in the order <b>2</b> > <b>1</b> > <b>4</b> > <b>3