Syntheses, spectroscopic and crystal structural studies of novel imidazo[4,5-f]1,10-phenanthroline derivatives and their Eu(III) ternary complexes with dibenzoylmethane

Abstract

Two novel ligands, 2-(4′-dimethylaminophenyl)imidazo[4,5-f]1,10-phenanthroline (L1) and 3-ethyl-2-(4′-dimethylaminophenyl)imidazo[4,5-f]1,10-phenanthroline (L2), and their europium(III) complexes with dibenzoylmethanate (DBM), Eu(DBM) 3(L1) and Eu(DBM) 3(L2), were synthesized and characterized by IR, UV–Vis and fluorescence spectroscopy, and thermogravimetric and differential thermal analyses (TG–DTA). The fluorescent intensity of Eu(DBM) 3(L2) is 18 times that of Eu(DBM) 3(L1). The crystal structures of Eu(DBM) 3(L1) and L2 were determined by single crystal X-ray diffraction. Each europium atom is coordinated by six oxygen atoms of three bidentate DBM anions and two nitrogen atoms from one bidentate L1, forming a distorted square antiprism. Highly resolved fluorescence spectroscopy of Eu(DBM) 3(L1) at 77 K revealed one Eu(III) site.