Temperature-dependent 3D structures of lanthanide coordination polymers based on dicarboxylate mixed ligands

Kittipong Chainok, Nutcha Ponjan, Chatphorn Theppitak, Phailyn Khemthong, Filip Kielar, Winya Dungkaew, Yan Zhou, Stuart R. Batten

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21 Citations (Scopus)

Abstract

Fourteen three-dimensional (3D) lanthanide coordination polymers (CPs) with dicarboxylate mixed ligands, [Ln(fum) 1.5 (H 2 O) 2 ]·0.5(H 2 bdc)·H 2 O (Ln = Sm (1), Tb (2)), [Ln 2 (fum) 2 (bdc)(H 2 O) 4 ]·2H 2 O (Ln = Sm (3), Eu (4), Tb (5), Er (6)), [Ln(fum) 0.5 (bdc)] (Ln = Sm (7), Eu (8), Tb (9), Er (10)), and [Ln 2 (bdc) 2 (ox)(H 2 O) 4 ]·0.7H 2 O (Ln = Sm (11), Gd (12), Tb (13), Dy (14)), have been synthesized hydrothermally from the self-assembly of lanthanide(iii) ions (Ln 3+ ), fumaric acid (H 2 fum), and terephthalic acid (H 2 bdc) in the presence of potassium hydroxide at different temperatures. The compounds fall into four classes. Compounds 1 and 2 were isolated from hydrothermal reactions performed at a relatively low temperature of 100 °C and found to crystallize in the triclinic space group P1. The 3D framework is assembled from 2D layers of [Ln(fum)(H 2 O) 2 ] units pillared by the chelating fum ligands and has 1D rhombic channels templated by H 2 bdc and lattice H 2 O molecules. The framework presents a binodal (4,5)-connected tcs topology with the point symbol (4 4 ·6 2 )(4 4 ·6 6 ). Raising the reaction temperature to 140 °C resulted in the formation of compounds 3-6. These materials crystallize in the monoclinic system with the polar space group P2 1 and feature a 3D network constructed from dinuclear {Ln 2 (OCO) 6 (H 2 O) 4 } units interlinked by fum and bdc ligands, showing a uninodal 6-connected two-fold interpenetrated pcu topology. The small channels of the framework are occupied by lattice H 2 O molecules. Further increase of the reaction temperature to 160 °C gave rise to the formation of compounds 7-10, crystallizing in the orthorhombic space group Pbca. The 3D framework is generated from 2D corrugated sheets of [Ln(fum)] 2+ bound by bdc ligands and contains no intercalated H 2 O molecules in the lattice. The framework possesses a trinodal (4,6,7)-connected net with the point symbol (4 2 ·6 4 ) 2 (4 6 ·6 8 ·8)(4 12 ·6 9 ) 2 . Finally, compounds 11-14 contained an in situ generated oxalate (ox) ligand formed under hydrothermal conditions conducted at a high reaction temperature of 180 °C. These compounds crystallize in the monoclinic space group P2 1 /c and possess a 3D open framework consisting of a dinuclear [Ln 2 (ox)(H 2 O) 4 ] 2+ unit linked by bridging bdc ligands and has small void channels occupied by lattice H 2 O molecules. The frameworks were topologically simplified as a binodal (4,5)-connected tcj/hc net with a total point symbol of (4 2 ·5 2 ·7 2 )(4 2 ·5 3 ·7 5 ). In the solid state at room temperature, the Tb (2, 5, 9, and 13) and Eu (4 and 8) compounds emit green and red light, respectively.

Original languageEnglish
Pages (from-to)7446-7457
Number of pages12
JournalCrystEngComm
Volume20
Issue number46
DOIs
Publication statusPublished - 14 Dec 2018

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