Structural diversity and properties of coordination polymers built from a semi-rigid tetradentenate carboxylic acid

Abstract

By using a semi-rigid tetracarboxylate ligand 5,5′-(1,4-phenylenebis(methylene))bis(oxy)diisophthalic acid (H₄L), three novel coordination polymers were synthesized solvothermally and characterized by single-crystal X-ray diffraction, thermogravimetric, photoluminescent and gas adsorption studies. Compound [Zn(H₂L)(H₂O)₂] (1) is a two-dimensional (2D) network with sql/Shubnikov topology built from the 4-connecting Zn₂(OOC)₂ cluster and bridging ligand H₂L²⁻. Compound [Co₂(H₃L)₂(H₂L)(H₂O)₂]·5H₂O (2) is a one-dimensional (1D) zigzag chain-like polymer made of 2-connecting ligand H₂L²⁻ and Co₂O₆(H₂O)₄ clusters, which form a 3D network through hydrogen bonding interactions. [Cd₃(L)₂]·(H₃O)₂(H₂O)(DMF)₄ (3) possesses a rare (4,8)-connected flu (CaF₂) net built from 8-connecting Cd₃ clusters and 4-connecting L ligands. In three complexes, the ligand H₄L exhibits diverse coordination configurations and modes owing to its flexibility. Upon excitation at room temperature, complexes 1 and 3 exhibit strong violet and blue emissions, respectively. N₂ gas adsorption measurements at 77 K showed that compound 3 possesses permanent porosities.