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 (H(2)hisp) with Sm(NO3)(3)center dot 6H(2)O or SmCl3 center dot 6H(2)O in the presence of NaOH, two kinds of samarium coordination polymers, [Sm(H(2)hbtc)(ox)(0.5)(H2O)(3)](n)center dot nH(2)O (1) (H(2)hbtc(2-) = 6-hydroxy-1,2,4-benzenetricarboxylate) and (Sm(hisp)(Hhisp)(H2O)(2)](n)center dot 2nH(2)O (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 (H(2)hbtc(2-)) 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. (c) 2008 Elsevier Inc. All rights reserved.