A new family of dinuclear lanthanide complexes exhibiting luminescence, magnetic entropy changes and single molecule magnet behaviors

Abstract

A new family of lanthanide complexes based on a tetrazole-1-acetate ligand and a 1,10-phenanthroline co-ligand were synthesized and characterized by IR spectroscopy, thermogravimetric analyses, powder X-ray diffraction and single-crystal X-ray diffraction, and their formula is [Ln₂(μ-Cl)₂(1-tza)₂(phen)₄](ClO₄)₂ [Ln = Eu (1), Tb (2), Gd (3), Dy (4); 1-Htza = tetrazole-1-acetate, phen = 1,10-phenanthroline]. They show dinuclear structures bridged by mixed μ-COO⁻_1-tza and μ-Cl⁻. The solid-state luminescence emission properties of 1 and 2 exhibit the characteristic emission bands of Ln cations with a lifetime of 1.49 ms and 0.20 ms, respectively. Magnetic studies reveal that 3 shows a magnetocaloric effect with −ΔS_m^max = 18.5 J kg⁻¹ K⁻¹ at 3 K for ΔH = 5 T and 4 displays a single-molecule magnet behaviour with U_eff of 15.19 K.