FULL PAPER DOI: 10.1002/ejic.200800463 H-Bonded Porous Supramolecular Network of a Cu II Complex Assisted by Assembled 2D Sheet of Chair Form Hexameric Water Cluster Kafeel Ahmad Siddiqui, [a] Gopal K. Mehrotra,* [a] Jerzy Mrozinski, [b] and Raymond J. Butcher [c] Keywords: Transmetallation / Copper complex / Hydrogen bonds / Porous supramolecular network The supramolecular network of the complex having the for- mula [Cu(nicot) 2 ·2NH 3 ·2H 2 O]·6H 2 O 1 has been synthesized by transmetallation of the Zn–nicotinate complex by Cu II ions and its crystallization in an ionic liquid. The supramolecular network of 1 shows unique H-bonding in the sense that it not only participates in the formation of nanoporous 2D chains but also forms cyclic hexameric water cluster that adopt an Introduction Pronounced interest has recently been focused on the synthesis and characterizations of H-bonded supramolec- ular materials which offer themselves as attractive molecu- lar models connecting molecular to supramolecular chemis- try. Due to the reversible nature of the intermolecular inter- actions and relatively poor stability, these structures seem to have dynamic properties not found in covalent bonded coordination polymers. It is known that in aqueous solution aggregates of water molecules (H 2 O) n clusters help stabilize both natural and synthetic supramolecular species. In this relevance, self-assembled H-bonded water clusters found trapped in a crystal host are of particular interest because of their unusual properties and vital role played by them in many physical, chemical and biological processes. [1,2] A number of small water clusters in diverse surroundings have been widely investigated both from theoretical and experi- mental aspects in order to better understand anomalous na- ture of bulk water or ice I h [1] These H-bonded water clusters of different morphologies such as tetramers, pentamers, hexamers, heptamers, octamers and decamers or polymeric chains, tape or layer structures have been found trapped in organic molecular crystals as well as in metal-organic frameworks. [3,4,5] Of these, the water hexamer, a simple supramolecular analogue of cyclohexane, is of particular [a] Department of Chemistry, M. N. National Institute of Technology Allahabad, 211004, U.P., India E-mail: gkmehrotra@mnnit.ac.in [b] Faculty of Chemistry, Wroclaw University, F. Joliot-Curie 14 Street, 50-383 Wroclaw, Poland [c] Department of Chemistry, Howard University, Washington, DC 20059, USA Supporting information for this article is available on the WWW under http://www.eurjic.org or from the author. © 2008 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim Eur. J. Inorg. Chem. 2008, 4166–4172 4166 ice-like chair conformation, which together with octanuclear H-bonded rings extend the network into a 3D open frame- work. X-ray structural analysis, FTIR, thermal analysis, EPR and magnetic properties have been used to characterize this compound. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008) interest in the sense that beside existing in different iso- energic isomeric forms it also exhibits some of the proper- ties found in bulk water. [6,7,8] Hexameric water also forms a liquid crystalline lattice that is involved in cellular com- munication, intracellular water movement, enzyme function and many other metabolic processes. In addition to the above-mentioned fundamental importance, the H-bonded aggregates have been reported to possess interesting mag- netic properties. [4a,5b] In this context, we have noticed that in order to strategi- cally design and synthesize metal-organic framework (MOF) structures where metal complexes act as binder for small water clusters, most of the workers have so far adopted the route of one-pot synthesis. [3,4,5] To date there is no report on the synthesis of porous supramolecular net- work of a metal complex formed by transmetallation. Here we describe the preparation, crystal structure and magnetic studies of a 3D porous supramolecular network of the com- plex [Cu(nicot) 2 ·2NH 3 ·2H 2 O]·6H 2 O(1) formed by transme- tallation of Zn–nicotinate complex by Cu II ion and its crystallization in an ionic liquid (25 % ammonia solution) that is stabilized by an intricate array of H-bonded interac- tions involving contributions from solvent water clusters, namely a water hexamer [(H 2 O) 6 ] with ice-like molecular arrangement. Results and Discussion Description of the Supramolecular Network The synthesis of the complex 1 is shown in Scheme 1.