Six lanthanide supramolecular frameworks based on mixed m-/p-hydroxybenzoic acid and 1,10-phenanthroline tectons: syntheses, crystal structures, and properties

Abstract

To further explore the research of the coordination possibilities of lanthanide ions with m-/p-hydroxybenzoic acid isomers in the presence of chelating N-donor ligand 1,10-phenanthroline (phen), six lanthanide supramolecular frameworks based on 3- and 4-hydroxybenzoic acids, namely [Dy(m-L)(m-HL) (phen)]center dot H2O (1) (m-H2L = 3-hydroxybenzoic acid), [Ln(m-HL)(3)(phen)] (Ln = Gd for 2 and Tb for 3), [Ln(p-HL)(3)(phen)(H2O)] (Ln = Dy for 4, Gd for 5, and Tb for 6; p-H2L = 4-hydroxybenzoic acid), were synthesized and characterized. Structural analyses reveal that complex 1 has a two-dimensional (2-D) sheet structure while complexes 2 and 3 take the dinuclear structures in the 3-hydroxybenzoate derivatives. In the 4-hydroxybenzoate derivatives, complexes 4-6 are isostructural and incorporated by monomeric units. Finally, all the complexes exhibit three-dimensional (3-D) supramolecular frameworks (bcu net for I; bct nets for 2, and 4-6; hex net for 3) with the aid of abundant hydrogen bonding, pi center dot center dot center dot pi and C-H center dot center dot center dot pi interactions. The results reveal that the different positions of the-OH substituent and coordination modes of hydroxybenzoic acids adjust the final coordination networks. Moreover, the magnetic and luminescent properties of the complexes have also been investigated and discussed. (C) 2016 Elsevier Ltd. All rights reserved.