Syntheses, characterization, luminescence, and thermal decomposition mechanism of four lanthanide complexes with 4-ethylbenzoic acid and terpyridine

Abstract

Four new lanthanide 4-ethylbenzoic acid complexes [Ln(4-EBA)3(terpy)H2O]2 {Ln = Sm(1), Eu(2), Tb(3), Dy(4), 4-EBA = 4-ethylbenzoate, terpy = 2,2′:6′,2′′-terpyridine} have been synthesized. The complexes are characterized by means of elemental analysis, IR, UV, and XRD. The crystals [Ln(4-EBA)3(terpy)H2O]2 {Ln = Eu(2), Tb(3)} are characterized by single-crystal X-ray diffraction. These complexes feature a tridentate terpyridine ligand, 4-ethylbenzoic acid ligands exhibiting multiple binding modes, bidentate, bridging bidentata, and monodentate, and a bound water molecule. The Ln3+ ions have a typical coordination number of nine with a distorted monocapped square antiprism. The thermal decomposition mechanism of the complexes has been investigated by TG/DSC–FTIR technology, and IR spectra of the evolved gases show complexes broken down into H2O, CO2, and other gaseous molecules as well as the gaseous organic fragments. Moreover, the complexes [Ln(4-EBA)3(terpy)H2O]2 exhibit characteristic luminescence, indicating that ligands can act as sensitizing chromophore in these systems.