Assembly of 1D and 2D zinc(II) coordination polymers from flexible polyimidazolyl-based ligands

Reactions of Zn(NO3)2∙ 6H2O with 1,3,5-tris(imidazol-1-ylmethyl)-2,4,6-trimethylbenzene (titmb) in the presence of 1,4-benzenedicarboxylic acid (1,4-H2BDC) or 1,3-benzenedicarboxylic acid (1,3-H2BDC) under hydrothermal conditions afforded one 1D and one 2D coordination polymers [Zn3(titmb)2(1,4-BDC)3(H2O)6] (1) and [Zn2(titmb)(1,3-BDC)2(H2O)] (2), respectively. Similar reactions of Zn(NO3)2∙ 6H2O with 1,3-bis(imidazol-1-ylmethyl)-2,4,6-trimethylbenzene (bitmb) and 1,4-H2BDC gave rise to one 2D coordination polymer [Zn2(bitmb)2(1,4-BDC)2] (3). Compound 1 has a 1D linear chain formed from linking 24-membered [Zn2(titmb)2] metallamacrocycles and [Zn(1,4-BDC)(H2O)2] units via imidazolyl groups of titmb ligands. Compound 2 has a 2D network assembled from connecting spiral [Znn(1,3-BDC)n] chains with titmb linkers, while compound 3 also has a 2D network formed by linking 24-membered [Zn2(bitmb)2] metallamacrocycles via 1,3-BDC bridges. The ligands titmb and bitmb in compounds 1–3 adopt less-common cis–trans–trans and cis–trans conformations, respectively. Their thermal and photoluminescent properties were also investigated.