Cation-dependent structural diversity of zinc(II), calcium(II) mono- and binuclear complexes of aryl-imidazo-1,10-phenanthroline derivatives

Abstract The syntheses of azacrown-containing aryl-imidazophenanthroline by reaction of 1,10-phenanthroline-5,6-dion with 4-(1.4.7.10-tetraoxa-13-azacyclopentadecan-13-yl)benzaldehyde producing the ligand 2 in high yield is described. Examination of their Zn(II), Ca(II) and mixed complexes by UV/Vis and NMR spectroscopy suggests electronic communication between the two metal centers of ligand 2 . Stability constants, determined by spectrophotometric titration, indicate that the Zn(II) possesses higher affinity toward phenanthroline residue than Ca(II) and does not bind with azacrown-ether residue. This selectivity allows to prepare a mixed Zn(II)/Ca(II) complex.