Iron(III), nickel(II) and cadmium(II) complexes of triazamacrocyclic ligand with pendant nitrile groups 1,4,7-tris(cyanomethyl)-1,4,7-triazacyclononane: Synthesis, structural characteristics and artificial nuclease activity

Abstract

Fe(III), Ni(II) and Cd(II) complexes with nitrile-functionalized triazamacrocycle were prepared and structurally characterized. The Fe(III) macrocyclic complex features a 1D linear water chain situated in the hexagonal channel of the chiral supramolecular framework. On treatment with supercoiled DNA, the Fe(III) complex shows efficient nuclease activity under near physiological conditions. Three novel transition metal complexes with 1,4,7-tris(cyanomethyl)-1,4,7-triazacyclononane (L) were synthesized and structurally characterized. In complex [FeLCl 3 ]·2H 2 O ( 1 ), three N-donors from the macrocyclic backbone and three chloride anions complete the coordination polyhedron around Fe(III) and lead to a neutral [FeLCl 3 ] unit. The neutral Fe(III) units of the same chirality are linked through weak interactions into 3D supramolecular network with hexagonal channels. Guest water molecules trapped inside the channel are associated into an unprecedented 1D linear chain. The crystal structures of complexes [NiL(CH 3 CN) 3 ](ClO 4 ) 2 ·0.5H 2 O ( 2 ) and [CdL(CH 3 CN) 3 ](ClO 4 ) 2 ·0.5H 2 O ( 3 ) reveal that the metal center lies in a distorted octahedral N6 environment with three acetonitrile occupying the remaining coordination sites opposite to the macrocyclic ring. The artificial nuclease activity of redox-active complex 1 towards pMD–AMT plasmid DNA was assessed by gel electrophoresis. As a result, complex 1 can effectively cleave supercoiled DNA under near physiological conditions with/without H 2 O 2 in a time- and complex concentration-dependent manner.