Dimensionality of luminescent coordination polymers of magnesium ions and 1,1′-ethynebenzene-3,3′,5,5′-tetracarboxylic acid modulated by structural inducing agents

Solvothermal reactions of aromatic 1,1′-ethynebenzene-3,3′,5,5′-tetracarboxylic acid (H(4)EBTC) and Mg(2+) salts in the presence of different supporting ligands afforded the coordination polymers [Mg(H(2)EBTC)(DMF)(2)(H(2)O)(2)] (1), [Mg(3)(HEBTC)(2)(H(2)O)(4)]·solvent (2) and [Mg(2)(EBTC)(H(2)O)(5)]·solvent (3). The crystal structures of 1–3 were determined by the single crystal X-ray diffraction technique, where CP 1 showed a one-dimensional zigzag MgO(6) coordination octahedral chain structure; 2 exhibited a two-dimensional MgO(6) coordination octahedral framework with trinuclear [Mg(3)(COO)(6)] SBUs, and 3 featured a three-dimensional MgO(6) coordination octahedral framework with binuclear [Mg(2)O(COO)(2)] SBUs. The various structures in CPs 1–3 of Mg(2+) ions with the H(4)EBTC ligand were ascribed to the conformational flexibility and the coordination mode diversity of the H(4)EBTC ligand. Interestingly, the zwitterionic supporting ligand 2-aminoterephthalic acid or 4-aminobenzenesulphonic acid played a vital role in the initial formation process of nuclear crystals but only as a structural induction agent, which modulated the dimensionality of these Mg(2+)-based CPs. Additionally, the three CPs emitted bright blue luminescence at ambient conditions, and the emission lifetimes and absolute quantum yields were also investigated.