Cd(II)-coordination polymers based on tetracarboxylic acid and diverse bis(imidazole) ligands: Synthesis, structural diversity and photoluminescence properties

Three new Cd(II)-coordination polymers, namely, {[Cd-2(mu(6)-ao(2)btc)(mu-1,5-bipe)(2)].2H(2)O}(n) (1), {[Cd-2(mu(6)-ao(2)btc) (mu-1,4-bix)(2)](n)-2DMF} (2) and {[Cd-2(mu(8)-abtc)(mu-1,4-betix)].DMF.H2O}(n) (3) (ao(2)btc=di-oxygenated form of 3,3',5,5'-azobenzenetetracarboxylate, 1,5-bipe: 1,5-bis(imidazol-lyl)pentane, 1,4-bix=1,4-bis(imidazol-lylmethyl)benzene, 1,4-betix=1,4-bis(2-ethylimidazol-lylmethyl)benzene) were synthesized with 3,3',5,5'-azo-benzenetetracarboxylic acid and flexible, semi-flexible and semi-flexible substituted bis(imidazole) linkers. They were characterized by IR spectroscopy, elemental analysis, single-crystal X-ray diffraction, powder X-ray diffractions (PXRD) and thermal analyses (TG/DTA). Complexes 1-3 exhibited structural diversities depending on flexible, semi-flexible and semi-flexible substituted bis(imidazole) ligands. Complex 1 was 2D structure with 3,6L18 topology. Complex 2 had a 3D pillar-layered framework with the rare sqc27 topology. When semi flexible substituted bis(imidazole) linker was used, 3D framework of complex 3 was obtained with the paddlewheel Cd-2(CO2)(4)-type binuclear SBU. Moreover, thermal and photoluminescence properties of the complexes were determined in detailed.