Impact of Synthetic Variables on the Structural Diversity of Tb^III-Carboxylate Frameworks: Gas Adsorption, Magnetism, and Organocatalysis Investigations

In this work, three unique Tb^III-carboxylate frameworks with the formula {[Tb₂(OH)₂(H₂O)₂(abtc)]·2H₂O}_<i>n</i> (<b>1</b>), {[Tb₂(abtc)_1.5(H₂O)₃(DMA)]·H₂O}_<i>n</i> (<b>2</b>) and {[Tb₃(abtc)_2.5(H₂O)₄]·H₃O}_<i>n</i> (<b>3</b>), each displaying structural variations, have been successfully synthesized by the solvothermal reactions of Tb(NO₃)₃·6H₂O with the azo-containing ligand 3,3',5,5'-azobenzene tetracarboxylic acid (H₄abtc) under varying conditions. Detailed single-crystal X-ray diffraction (SC-XRD) analysis manifested a remarkable diversity in these structures, demonstrating various coordination patterns of Tb^III-metal nodes with the carboxylate groups of the organic linker, which contributed to the generation of intricate three-dimensional (3D) coordination networks with remarkable chemical resistance. Furthermore, frameworks <b>2</b> and <b>3</b>, characterized by porous networks containing two and three independent Tb^III-metal nodes, respectively, were both demonstrated to be efficient heterogeneous catalysts toward the cyanosilylation of imines under mild conditions with excellent reusability. In addition, direct current (<i>Dc</i>) magnetic susceptibility measurements conducted on frameworks <b>1</b>, <b>2</b>, and <b>3</b> indicated that there were obvious antiferromagnetic interactions among the Tb^III-metal nodes, which suggests the involvement of intricate <i>intra</i>- and <i>intertrimer</i> exchange channels, adding another fascinating dimension to their physical properties.