Unusual coordination mode of aroyl/acyl thiourea ligands and their π-arene ruthenium (II) piano-stool complexes: Synthesis, molecular geometry, theoretical studies and biological applications

Two mononuclear ruthenium complexes (1 and 2) with aroyl/acylthiourea as an ancillary ligand of type, [(eta(6)-p-cymene)RuCl(L-N,S)], where [L1 = 2,4-dichloro-N-(o-tolylcarbamothioyl)benzamide] and L2 = N-(phenylcarbamothioyl)cyclohexanecarboxamide] were synthesized and well characterized. The single crystal X-ray diffraction studies revealed the coordination mode and the geometry of the complexes. The two complexes adopted general piano-stool (three-legged) geometry with a novel coordination mode of aroyl/acylthiourea through amide N (anionic) and thiocarbonyl S (neutral). This type of monobasic bidentate coordination of the aroyl/acylthiourea ligand was witnessed the first time around the metal ion. The coordination of the complexes was well explained through geometric parameters and frontier molecular orbital parameter values computed at the B3LYP/SDD level. The synthesized complexes were also screened for their antibacterial, antifungal, antioxidant and in vitro antiproliferative activities. Complexes exhibited good antimicrobial agents against various pathogens. The antioxidant activity of the complex 2 has shown most potent activity with IC50 value of 48.55 +/- 1.7 mu M compared to the reference drug. In addition, the in vitro antiproliferative activity of the complex 2 showed excellent activity against HepG-2 cell line with the IC50 value of 24.30 +/- 1.20 mu M which is close to Doxorubicin standard drug.