Effect of coordination environment on the photophysical properties of luminescent europium(III) complexes

Abstract

A series of Eu(III) complexes with various neutral ligands (2,2':6',2"-terpyridine (T), diglyme (D), 1N-(2-dimethylamino)ethyl)-1N, 2N, 2N-trimethylethane-1,2-diamine (PT), di-(2-picolyl)-amine derivative (HT), and multidentate terpyridine derivative (DT)) were synthesized to investigate the effect of coordination environment on the sensitized luminescence of Eu(III) complexes. The nine coordination sites of the Eu3+ ion are occupied by three bidentate carboxylate moieties and one neutral ligand. The highest emission intensity is obtained for Eu3+- [NA]3 (PT), due to the difference in energy transfer efficiency and symmetry of the first coordination sphere of Eu3+ ion. But, the lowest emission intensity is obtained for Eu3+-[NA]3(T). Terpyridine may not play an important role antenna for photosensitizing Eu3+ ion. It could be attributed to the weak spectral overlap integral J value between its phosphorescence band and Eu3+ion absorption band. Therefore, different coordination environment of Ln3+ ion play an important role in providing sensitization of lanthanide ion emission.