Structural Characterization of Zinc(II)/Cobalt(II) Complexes of Chiral <i>N</i>-(Anthracen-9-yl)methyl-<i>N</i>,<i>N</i>-bis(2-picolyl)amine and Evaluation of DNA Photocleavage Activity

Abstract

We designed and synthesized a chiral ligand N-(anthracen-9-ylmethyl)-1-(pyridin-2-yl)-N-(pyridin-2ylmethyl)ethanamine (APPE) DNA photocleavage agent to investigate the effects of chirality of bis(2-picolyl)-amine on the DNA photocleavage activity of metal complexes. The structures of Zn II and Co II complexes in APPE were analyzed via X-ray crystallography and fluorometric titration. APPE formed metal complexes with a 1 : 1 stoichiometry in both the crystalline and solution states. Fluorometric titration was used to show that the Zn II and Co II association constants of these complexes (log K a s) were 4.95 and 5.39, respectively. The synthesized complexes were found to cleave pUC19 plasmid DNA when irradiated at 370 nm. The DNA photocleavage activity of the Zn II complex was higher than that of the Co II complex. The absolute configuration of the methyl-attached carbon did not affect DNA cleavage activity and, unfortunately, an achiral APPE derivative without the methyl group (ABPM) was found to perform DNA photocleavage more effectively than APPE. One reason for this may be that the methyl group suppressed the structural flexibility of the photosensitizer. These results will be useful for the design of new photoreactive reagents.