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

•Syntheses of azacrown-containing aryl-imidazophenanthroline.•Zn(II) and Ca(II) prefer to bind with phenanthroline residue upon complex formation.•Azacrown-containing aryl-imidazophenanthroline can form a mixed Zn(II)/Ca(II) complex.

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.

Graphical abstractNovel azacrown-containing aryl-imidazophenanthroline demonstrates the coordination of Zn(II) with the phenanthroline residue, whereas Ca(II) can bind with both phenanthroline and crown ether centers. This selectivity allows the preparing of a mixed Zn(II)/Ca(II) complex.Figure optionsDownload full-size imageDownload as PowerPoint slide