Syntheses, Crystal Structures, and Luminescence Properties of a Series of Novel Lanthanide Oxalatophosphonates with Two Types of 3D Framework Structures

Abstract

By introduction of oxalate as the second ligand, 12 novel lanthanide oxalatophosphonates with two types of three-dimensional (3D) framework structures, namely, [Ln2(H4L)(C2O4)3(H2O)]·3H2O (Ln = La (1), Ce (2), Pr (3), Nd (4), Sm (5), Eu (6), H4L = 3-pyridyl-CH2N(CH2PO3H2)2) and [Ln2(H4L)(C2O4)3(H2O)]·2H2O (Ln = Gd (7), Tb (8), Dy (9), Y (10), Er (11), Lu (12)), have been synthesized under hydrothermal conditions. Compounds 1−6 are isostructural and feature a 3D framework structure formed by the interconnection of the 3D network of {Ln2(C2O4)3} with one-dimensional chains of {Ln2(H4L)}6+. Compounds 7−12 are also isostructural and possess a novel 3D framework structure different from that in compounds 1−6. The interconnection of Ln(III) ions by chelating and bridging oxalate anions result in a lanthanide oxalate layer in the ac planes. These layers are further linked by H4L ligands to form a 3D framework. It is interesting that a type of right-hand helical chain is formed by H4L ligands bridging Er(2) ions running along the b-axis. The Nd, Eu, and Tb compounds exhibit strong luminescence in near-IR, red light, and green light regions, respectively.