In-situ carboxylation and synthesis of two novel Sm(III) coordination polymers assembled from 5-hydroxyisophthalate and nitrate, chloride in hydrothermal reaction

By reactions of 5-hydroxyisophthalic acid (H2hisp) with Sm(NO3)3·6H2O or SmCl3·6H2O in the presence of NaOH, two kinds of samarium coordination polymers, [Sm(H2hbtc)(ox)0.5(H2O)3]n·nH2O (1) (H2hbtc2−=6-hydroxy-1,2,4-benzenetricarboxylate) and [Sm(hisp)(Hhisp)(H2O)2]n·2nH2O (2), have been hydrothermal synthesized and characterized. Single-crystal X-ray analyses reveal that compound 1 features a novel two-dimensional (2D) stair-like structure with oxalate ligands and the new organic ligand (H2hbtc2−) but without 5-hydroxyisophthalate ligands, while compound 2 gives the expected product and displays a novel layer structure. The oxalate ligands have been formed via the in-situ reductive coupling of CO2 molecules released from the decomposition of carboxylate ligands with the reduction of NO3− and the new organic ligands have been formed via the in-situ carboxylation under the presence of NO3−. Reported herein are the syntheses of compounds 1 and 2, crystal structures and possible mechanism information regarding the in-situ carboxylation.

Graphical abstractHydrothermal reactions of Sm(NO3)3·6H2O or SmCl3·6H2O with 5-hydroxyisophthalic acid (H2hisp) have given rise to two different kinds of Sm(III) coordination polymers. Single-crystal X-ray analyses reveal that compound 1 features a novel 2D stair-like structure with oxalate and a new organic ligand, 6-hydroxy-1,2,4-benzenetricarboxylate, while compound 2 gives the normal product and displays a novel 2D layer structure. Oxalate ligands have been formed via the in-situ reductive coupling of CO2 molecules released from the decomposition of 5-hydroxyisophthalate ligands with the reduction of NO3− and the new organic ligands have been formed via the in-situ carboxylation under the presence of NO3−.Figure optionsDownload full-size imageDownload as PowerPoint slide