Ru(II)-η⁶-benzene complexes of dibenzosuberenyl appended aroyl/acylthiourea ligands: In vitro biomolecular interaction studies and catalytic transfer hydrogenation

A series of novel N-dibenzosuberene appended aroyl/acylthiourea ligands (L1-L4) and their Ru(II)-benzene complexes (1-4), [RuCl₂(η⁶-benzene)L] (L=monodentate aroyl/acylthiourea ligand) was synthesized and well characterized. The coordination mode of aroyl/acylthiourea ligand with Ru ion through S (neutral monodentate) donor atom was determined by single crystal X-ray diffraction analysis. In vitro Calf thymus DNA (CTDNA) and Bovine serum albumin (BSA) interaction of the complexes were investigated by UV-Visible, fluorescence spectroscopic and hydrodynamic methods. The results showed the intercalative mode of binding (in the order of 1 > 4 > 3 > 2) of the Ru(II)-benzene complexes with CT-DNA. The DNA (pUC19) cleavage study showed that the complexes cleaved DNA through a hydrolytic pathway. All the complexes have been thoroughly screened for their cytotoxicity against human liver carcinoma (HepG-2) and lung cancer (A549) cells under in vitro conditions. Complex 1 exhibited significant cytotoxic activity (IC₅₀=46.1 μM) towards HepG-2 cancer cell line. In addition to this, the prepared complexes have been utilized as catalyst precursors for transfer hydrogenation (TH) of ketones, aldehydes and nitro compounds using 2-propanol as a hydrogen source. The TH reactions proceeded with exceptional conversions (up to 99%) and the present catalytic system was extended to substituted aromatic/heterocyclic carbonyl and nitro compounds.