Seven Novel Lanthanide Oxalatophosphonates with Two Types of 3D Framework Structures Based on N-Morpholinomethylphosphonic Acid: Syntheses, Crystal Structures, and Luminescence Properties

Abstract

By using the N-morpholinomethylphosphonic acid as the phosphonate ligand and oxalate as the second metal linker, seven novel lanthanide(III) oxalatophosphonates with two types of 3D framework structures, namely, [Ln3(HL)(C2O4)4(H2O)4]·2H2O (Ln = Pr (1), Nd (2), Sm (3), H2L = O(CH2CH2)2NCH2PO3H2) and [Ln2(H2L)(C2O4)3(H2O)3]·H2O (Ln = Eu (4), Gd (5), Tb (6), Dy (7)), have been synthesized under hydrothermal conditions. Compounds 1−3 are isostructural and feature a complex 3D framework structure formed by the interconnection of 3D network of {Ln3(C2O4)4}+ with 1D chains of {Ln3(HL)}8+. Compounds 4−7 are isostructural and possess a 3D framework structure different from that in compounds 1−3. The interconnection of Ln(III) ions by chelating oxalate ligands lead to a lanthanide oxalate layer down the c-axis. These layers are linked by H2L ligands to form a 3D framework type with channel system down the a-axis. Luminescence properties of compounds 3, 4, 6 and 7 have also been studied.