Crystal structures and DNA-binding properties of PrIII complexes derived from 8-hydroxyquinoline-2-carboxaldehyde and three aroylhydrazines

Pr-III and three synthesized ligands, 8-hydroxyquinoline-2-carboxaldehyde-(benzoyl) hydrazone, 8-hydroxyquinoline-2-carboxaldehyde-(2'-hydroxybenzoyl) hydrazone, and 8-hydroxyquinoline-2-carboxaldehyde-( isonicotinyl) hydrazone, respectively, can form binuclear Pr-III complexes with 1 : 1 metal-to-ligand stoichiometry and nine-coordination at Pr-III indicated by X-ray crystal structural analyses. Ligands are dibasic tetradentate, binding to Pr-III through the phenolate oxygen, nitrogen of quinolinato unit, the C=N of methylene, and O-C=N-enolized and deprotonated from O=C-NH- of the aroylhydrazone side chain. One DMF binds orthogonally to the ligand plane from one side to the metal ion, while another DMF and a bidentate nitrate simultaneously bind from the other. Dimerization of the monomeric unit occurs through the phenolate oxygen leading to a central planar four-membered (PrO)(2) ring. The crystal structures are similar to each other and to other nine-coordinate lanthanide complexes with geometry of distorted edge-sharing mono-capped square-antiprism of [LnL(NO3)(DMF)(2)](2) (Ln =La-III, Nd-III, Sm-III, Eu-III, Tb-III, Dy-III, Ho-III, and Er-III) except for Yb-III with eight-coordinate Yb-III center with distorted edge-sharing dodecahedron of [YbL(NO3)(DMF)](2), derived from 8-hydroxyquinoline-2-carboxaldehyde and aroylhydrazines. The ligands and Pr-III complexes can bind to calf thymus DNA through intercalation with binding constants at 10(5) M-1 and probably be used as potential antitumor drugs.