Two novel thorium organic frameworks constructed by bi- and tritopic ligands

Two thorium organic frameworks, Th(BDC) 2 and Th(OH)(BCPBA) have been hydrothermally synthesized using 1,4-benzenedicarboxylic acid (H 2 BDC) and 3,5-bi(4-carboxyphenoxy)benzoic acid (H 3 BCPBA), respectively. The obtained two compounds were determined by single-crystal XRD, and they exhibited two new topologies. Th(BDC) 2 shows a 3-dimensional (4,4,8)-connected framework with the Schläfli symbol of (4 14 ·6 12 ·8 2 )(4 2 ·6 3 ·8)(4 4 ·6 2 ), and it is a mononuclear thorium(IV) complex. Th(OH)(BCPBA) possesses a (4,6)-connected topology with the Schläfli symbol of (4 15 ) 2 (4 6 ) 3 , and it has a dinuclear thorium(IV) asymmetric unit with the shortest Th–Th distances. Viewing along suitable directions, channels with different shapes can be found in the obtained two frameworks. Based on calculation with PLATON, the amount of void space is 21.9% and 13.5% in Th(BDC) 2 and Th(OH)(BCPBA), respectively. Density functional theory (DFT) studies revealed that the metal-ligand interactions were mainly of ionic character in both compounds and the hydroxyl ions might play an important role in the stability of dinuclear thorium(IV) of Th(OH)(BCPBA).