Published: March 11, 2011 r2011 American Chemical Society 1230 dx.doi.org/10.1021/cg101453m | Cryst. Growth Des. 2011, 11, 1230–1237 ARTICLE pubs.acs.org/crystal Zinc Coordination Polymers with 2,6-Bis(imidazole-1-yl)pyridine and Benzenecarboxylate: Pseudo-Supramolecular Isomers with and without Interpenetration and Unprecedented Trinodal Topology Jhen-Yi Lee, † Chih-Yuan Chen, † Hon Man Lee,* ,† Elisa Passaglia, ‡ Francesco Vizza, § and Werner Oberhauser* ,§ † Department of Chemistry, National Changhua University of Education, Changhua 50058, Taiwan, R.O.C. ‡ ICCOM-CNR, UOS Pisa, Area della Ricerca, via Moruzzi, 1, 56124, Pisa, Italy § Istituto di Chimica dei Composti Organometallici (ICCOM-CNR), Area di Ricerca CNR di Firenze, via Madonna del Piano 10, 50019 Sesto Fiorentino, Italy b S Supporting Information ’ INTRODUCTION Crystal engineering to synthesis rationally coordination polymers (CPs) or metalorganic frameworks (MOFs) attract much interest because of their potential applications as functional materials 15 in gas storage, 6 separation, 7 catalysis, 8,9 drug delivery, 10,11 the embed- ding of nanoparticles, 12 etc. Their fascinating architectures and topological networks also account for their wide interest. 1316 The use of rigid ligands, such as 4,4 0 -bipyridine (4,4 0 -bpy) 17,18 and 1,4-benzenedicarboxylate (1,4-bdc), 19,20 to obtain porous CPs have been well-documented. Recently, there is also a growing trend in using flexible ligands to obtain intriguing network architectures. 21 The use of flexible ligands not just allows the construction of coordination network with special properties and structures, but also provides opportunities to understand the details of a self-assembly process. However, in general, construction of CPs based on flexible ligands is difficult; the control in the final architectures is poor because of the possibility of diverse ligand conformations and the structural characterizations are somewhat more challenging. 21 Previously, we employed 2,6-bis(imidazole-1-yl)pyridine (2,6- bip) to construct chiral 1D zinc CPs of helical and zigzag chains. 22 The ligand is a hingelike molecule, 23,24 allowing certain degree of rotations around the CN bonds between the three rings. Thus such semirigid ligand allows slight conformational changes for the potential assembly of di fferent network architectures, but at the same time, greatly avoids the above-mentioned problems associated with flexible ligands. Thus, contrasting to the recent trend in using flexible ligands to obtain intriguing network architectures, 21 we employed a combination of semirigid 2,6-bip ligand and an additional rigid ligand of benzenecarboxylate to construct novel multidimensional (2D and 3D) zinc CPs. The strategy successfully yields three new polymeric materials, {Zn(1,4-bdc)(2,6-bip) 3 2H 2 O} n (1), {Zn(1,4-bdc)(2,6- bip) 3 DMF} n (2), and [Zn 2 (μOH)(1,3,5-btc)(2,6-bip) 3 H 2 O] n (3). Notably, 1 and 2 are 2D pseudo-supramolecular isomers, 25,26 which shows undulating (4,4) networks with and without inter- penetration, respectively. Compound 3 exhibits a 3D array with an unprecedented topology. The networks in 1 and 2 show reversible solvent incorporation properties. ’ RESULTS AND DISCUSSION Synthesis of CPs. Compound 1 was prepared under hydro- thermal condition by heating a basic mixture (pH = 79) of Received: November 1, 2010 Revised: February 10, 2011 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(NO 3 ) 2 3 6H 2 O, 2,6- bip, and terephthalic acid under basic condition affords [Zn(1,4-bdc)(2,6-bip) 3 2 H 2 O] 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) 3 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 [Zn 2 (μOH)(1,3,5-btc)(2,6-bip) 3 H 2 O] n (3) (btc = benzenetricarboxylate), which exhibits a (3,4,6)-connected 3D frame- work with an unprecedented {5.6.7} 2 {5 2 .6.7.8 2 } 2 {5 4 .6 2 .7 3 .8 4 .9 2 } topology. Com- pound 1 and 2 show reversible solvent incorporation properties.