Cd(II)-Coordination Polymers Based on Tetracarboxylic Acid and Diverse Bis(Imidazole) Ligands: Synthesis, Structural Diversity and Photoluminescence Properties

Abstract

Three new Cd(II)-coordination polymers, namely, {[Cd<inf>2</inf>(μ<inf>6</inf>-ao<inf>2</inf>btc)(μ-1,5-bipe)<inf>2</inf>]·2H<inf>2</inf>O}<inf>n</inf> (1), {[Cd<inf>2</inf>(μ<inf>6</inf>-ao<inf>2</inf>btc)(μ-1,4-bix)<inf>2</inf>]<inf>n</inf>·2DMF} (2) and {[Cd<inf>2</inf>(μ<inf>8</inf>-abtc)(μ-1,4-betix)]·DMF·H<inf>2</inf>O}<inf>n</inf> (3) (ao<inf>2</inf>btc=di-oxygenated form of 3,3′,5,5′-azobenzenetetracarboxylate, 1,5-bipe: 1,5-bis(imidazol-1yl)pentane, 1,4-bix=1,4-bis(imidazol-1ylmethyl)benzene, 1,4-betix=1,4-bis(2-ethylimidazol-1ylmethyl)benzene) were synthesized with 3,3′,5,5′-azobenzenetetracarboxylic 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<inf>2</inf>(CO<inf>2</inf>)<inf>4</inf>-type binuclear SBU. Moreover, thermal and photoluminescence properties of the complexes were determined in detailed. © 2016 Elsevier Inc.