Zinc Coordination Polymers with 2,6-Bis(imidazole-1-yl)pyridine and Benzenecarboxylate: <i>Pseudo</i>-Supramolecular Isomers with and without Interpenetration and Unprecedented Trinodal Topology

Abstract

The ligand combination of semirigid 2,6-bis(imidazole-1-yl)pyridine (2,6-bip) and rigid benzenecarboxylate allow the isolation of three new zinc coordination polymers. Hydrothermal synthesis between Zn(NO3)2·6H2O, 2,6-bip, and terephthalic acid under basic condition affords [Zn(1,4-bdc)(2,6-bip)·2H2O]n (1) (1,4-bdc =1,4-benzenedicarboxylate), which shows an undulating 2D (4,4)-network with 2-fold interpenetration. Contrastingly, solvothermal synthesis with identical starting materials in DMF, yields [Zn(1,4-bdc)(2,6-bip)·DMF]n (2), which exhibits noninterpenetrating 2D (4,4)-network. Thus 1 and 2 are pseudo-supramolecular isomeric pair, illustrating the strong effect of guest solvents in controlling the entanglement. A similar hydrothermal reaction to 1 but using 1,3,5-benzenetricarboxylic acid instead yields [Zn2(μ−OH)(1,3,5-btc)(2,6-bip)·H2O]n (3) (btc = benzenetricarboxylate), which exhibits a (3,4,6)-connected 3D framework with an unprecedented {5.6.7}2{52.6.7.82}2{54.62.73.84.92} topology. Compound 1 and 2 show reversible solvent incorporation properties.