Copper(II) and manganese(II) picrate complexes with the V-shaped ligand 1,3-bis(1-methylbenzimidazol-2-yl)-2-thiapropane: preparation, structure, DNA-binding properties and antioxidant activities

A V-shaped ligand, 1,3-bis(1-methylbenzimidazol-2-yl)-2-thiapropane (L), and its copper(II) and manganese(II) picrate complexes have been synthesized and characterized. The compositions of the complexes are [Cu(L)(2)](pic)(2)center dot 2DMF (1) and [Mn(L)(pic)(2)] (2), respectively. The crystal structure of complex 1 reveals a distorted tetrahedral geometry provided by four N donors from two ligands. Complex 2 is six coordinated, with a distorted octahedral geometry. Experimental studies of the DNA-binding properties indicated that the free ligand and both complexes bind to DNA via the intercalation mode, and the order of the binding affinity is L > 1 > 2. Antioxidant tests in vitro show that the Cu(II) complex possesses significant antioxidant activity against superoxide and hydroxyl radicals, with better scavenging effects than mannitol and vitamin C.