Molecular cubes

The molecular cube [(pzTp)Fe(CN)3]4[Co(pz)3CCH20H]4 (C104)4 (266) based on the same combination of transition metal ions as the aforementioned PB analogue also was reported to exhibit CTIST and photomagnetic behavior (Fig. 69). 

Efforts to incorporate transition-metal ions of the second or third series that possess large spin-orbit coupling in order to enhance the overall anisotropy of the molecular clusters is one of the possibilities that chemists try to explore. Dunbar and coworkers reported the preparation of an octanu-clear complex of formula [(MnCl)4(Re(triphos)(CN)3)4] from the reaction of (Et4N)[Re(triphos)(CN)3] and MnCl2 in a mixture of acetone and acetonitrile under refiux. The complex has a cubic structure similar to Cr4Co4, where the metal ions occupy the vertices of the molecular cube (Fig. 12) [38]. 

An interesting property of cyanide-bridged molecular cubes is their ability to bind alkali metals (especially and Cs" ) selectively within the cube interior. Crystallographic analysis of a Rh-Mo molecular cube indicates bond formation between the cationic guest and the cube s CN edges. When K is encapsulated, the ion is distributed over two equivalent positions, both slightly displaced from the cube center. Encapsulated cesium ions, on the other hand, occupy a central position. The locational differences reflect differences in ionic radii 2.02 and 1.78 A for Cs" and K, respectively, with coordination numbers of 12 for each. The structural differences translate into a nearly 4000-fold preference for uptake of Cs versus from salt solutions, where the difference was evaluated competitively via Cs-NMR measurements. 

One simple and elegant example of supramolecular self-assembly is the synthesis of a molecular cube by Jim Thomas from the University of Sheffield,... 

The temperature dependence of the magnetic susceptibility for the latter eompound was measured. A fit of the data to the Curie-Weiss law gives an effective magnetic moment of 7.5 //b associated with a g value of 1.97 corresponding to four isolated A= 3/2 Cr ° ions per molecular cube. 

Argent SP, Adams H, Harding EP, Ward MD (2006) A closed molecular cube and an open book two... 

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