Lanthanide Contraction and Temperature-Dependent Structures of Lanthanide Coordination Polymers with Imidazole-4,5-Dicarboxylate and Oxalate

Three series of two-dimensional (2D) lanthanide coordination polymers of [Ln(HIDC)(OX) 0.5 (H 2 O) 2 ] n ·(H 2 O) n ( 1Ln ) (Ln = Pr and Nd), [Ln(HIDC)(OX) 0.5 (H 2 O) 2 ] n ·(H 2 O) n ( 2Ln ) (Ln = Eu and Tb), and [Ln(HIDC)(OX) 0.5 (H 2 O)] n ( 3Ln ) (Ln = Pr, Nd, Eu, and Tb) have been prepared by reacting Ln(NO 3 ) 3 ·6H 2 O with imidazole-4,5-dicarboxylic acid (H 3 IDC) and oxalic acid (H 2 OX) at different temperatures under hydrothermal conditions. The results of structural analyses indicate that 1Ln and 2Ln are supramolecular isomers, in which 1Ln displays a 2D monolayer structure of [Ln(HIDC)(OX) 0.5 (H 2 O) 2 ] n with a (4.5 2 )(4.5 3 .7 2 ) topology network, while 2Ln shows a different 2D monolayer structure containing alternating one-dimensional (1D) left-handed and right-handed helical chains of [Ln(HIDC)] ∞ bridged by OX 2− . 3Ln has a 2D double-layer structure consisting of oxalate pillared [Ln(HIDC)(H 2 O)] n n+ layers. The effect of lanthanide contraction and of temperature on the structures of 1Ln-3Ln was investigated. The structure related luminescent properties of 2Eu and 3Eu, as well as 2Tb and 3Tb, were also examined.