Syntheses, crystal structures, luminescence and thermal properties of three lanthanide complexes with 2-bromine-5-methoxybenzoate and 2,2:6′,2″-terpyridine

Abstract

Three new mononuclear lanthanide complexes [Ln(2-Br-5-MOBA)3(terpy)(H2O)] (Ln = Gd (1), Tb (2), Er (3); 2-Br-5-MOBA = 2-bromine-5-methoxybenzoate; terpy = 2,2:6′,2″-terpyridine) have been successfully synthesized and characterized by single-crystal X-ray diffraction. The complexes 1–3 were isostructural and eight-coordinated, which is different from the binuclear structure of the previously reported complexes. The molecular structure of complexes 1–3 is very interesting: two adjacent mononuclear units are connected through hydrogen bonding giving rise to a pseudo binuclear structure. These pseudo binuclear units are further linked via O–H⋯Br hydrogen bonds and slightly offset π–π stacking interactions to from 1D and 2D supramolecular structures. The thermal decomposition mechanism of complexes 1–3 was studied by TG analysis and further authenticated by TG/DSC-FTIR techniques. The solid-state luminescent property of complex 2 was investigated at room temperature. The result indicates that Tb (III) complex appear to be promising candidate for the application as green luminescent material.