Effect of lanthanide contraction and rigid ligand on the structure of salen-type lanthanide complexes

Abstract

Three types of phenolate oxygen-bridged N,N′-bis(2-oxy-3-methoxybenzylidene)-1,2-diaminophenylene 3d–4f heteronuclear and 4f tetranuclear complexes, namely, [(LZnCl)PrCl₂(CH₃OH)₂]₂ (1), [(LZnCl)LnCl(OAc)(CH₃OH)] (Ln = Tb (2) and Dy (3)) and [{(LLu₂)(OAc)₂(H₂O)(OH)}₂(ZnCl₄)]·2H₂O (4) are obtained by reactions of H₂L (H₂L = N,N′-bis(2-oxy-3-methoxybenzylidene)-1,2-phenylenediamine), LnCl₃·6H₂O (Ln = Pr, Tb, Dy and Lu) and Zn(OAc)₂·2H₂O in CH₃OH/CH₂Cl₂. X-Ray crystallographic analysis reveals that complex 4 possesses a novel defect-dicubane core, where four Lu³⁺ ions are inserted into the two sets of N₂O₂ and O₂O₂ cavities among the two tail-to-tail ligands. The structural investigations unambiguously testify that the lanthanide contraction and the rigid ligand cooperatively affect the formation of complexes 1–4, where Ln³⁺ ions with large, medium and small radius are composed in three different structures. The fluorescent spectrum of complex 2 exhibits the characteristic metal-centred fluorescence of Tb³⁺ ions.