Ionothermal synthesis of a new cobalt metal-organic framework based on tetranuclear cobalt clusters

A new metal-organic network (EMIM)[Co-2(hip)(2)(mu(3)-OH)]center dot H2O (1), (H(2)hip = 5-hydroxyisophthalic acid and EMIM = 1-ethly-3-methylimidazolium), has been synthesized by the ionothermal reaction of cobalt nitrate, H(2)hip and [EMIM]Br ionic liquid. Single-crystal X-ray diffraction analysis reveals that I exhibits a two-dimensional (2D) bilayer constructed from tetranuclear [Co-4(mu(3)-OH)(2)] building units and hip(2-) linkers. There are square cavities with the dimension of 10.161 x 10.868 angstrom. The [EMIM](+) cations are located in the cavities, which have the hydrogen bonding interactions with the bilayer. Further more, the strong hydrogen bonds between the carboxylate and hydroxyl oxygen atoms of hip(2-) ligands and lattice water molecules extend the 2D layer into a 3D supramolecular network. The magnetic properties of I have been investigated by variable-temperature magnetic susceptibility and magnetization measurements, and the results reveal that there exist anti ferromagnetic interactions. Crown Copyright (C) 2009 Published by Elsevier B.V. All rights reserved.