Group II complexes of N- and O-donors Mixed-ligands as anticancer agents

Reactions of 1,10-phenanthroline (phen), p-amino benzoic acid (paba) and cinnamic acid (cina) with MCO3 (M = Mg, Ca, Sr) yielded two mononuclear magnesium complexes [{Mg(phen)(H2O)(4)}(phen)(paba)(2)] (1) and [{Mg(phen)(H2O)(4)}(phen)(cina)(2)] (2) and two one dimensional chains of both calcium and strontium [Ca (phen)(cina)](n) (3), and [Sr(phen)(cina)] n (4) respectively. The structures were characterized by a variety of analytical techniques including IR, UV-Vis, H-1 NMR, elemental analysis, and single crystal X-ray diffraction analysis. In these complexes, phen binds via an N,N'- chelate pocket, while the monoanionic paba(-)/cina(-) ligands either remains uncoordinated (in case of 1 and 2) or coordinated in a tridentate fashion (in case of 3 and 4). Complexes 1, 3 and 4 crystallize in the same orthorhombic space group Pbcn while complex 2 crystallizes in triclinic space group P1. In complex 1 and 2, Mg2+ cation adopts a distorted six-coordinate octahedral geometry comprising an [N(2)O4] donor set while in complexes 3 and 4, Ca2+ and Sr2+ cations adopt a distorted eightcoordinate geometry comprising [N2O6] donor sets. Complexes 1, 2 and 4 were found to be potent anticancer against oral cancer cell line i.e. CAL-27 with IC50 1.85 +/- 0.11, 2.98 +/- 1.2 and 5.05 +/- 0.35 respectively while complex 3 was inactive.