Octahedral Systems Oh, O

We will now illustrate four octahedral hosts related to the Platonic solids. Three are based upon the cube while one possesses features of both a cube and an octahedron. 

The first is a cyclophane-based system reported by Murakami et al. (Fig. 9.12a). [31] The sides of the host consist of tetraaza-[3.3.3.3]paracyclophane units, and its octaprotonated cation has been shown to bind anionic guests. The molecule possesses 48 asymmetric units of [(N/3)-(CH2)- (C6H4)/2 ]/2. 

The second is a polyoxovanadate, [(V06)(RP03)8]+ (R = tBu, OSiMe3), reported by Zubieta et al. [32] and Thom et al. [33] which consists of V05 pyramids and phos-phonate ligands (Fig. 9.12b). The vanadium atoms of the shell are located at the vertices of an octahedron, while the phosphorus atoms are located at the comers of a cube, thus displaying the dual relationship of these polyhedra. In both cases, the host has been shown to complex a chloride ion. 

The third is a gold selenide cube, [NaAui2Se8]3, reported by Kanatzidis et al. [34] The anion is made up of eight selenium atoms and 12 gold atoms. A sodium cation occupies the center of the complex. 

The fourth is a cube synthesized by Chen and Seeman, the components of which are based upon DNA (Fig. 9.12c). [35] The directionality and ability of the double helix to form branched junctions are exploited for the edges and vertices, respectively. Interestingly, each face of this molecule forms a cyclic strand which is catenated with strands of adjacent faces. Molecular modeling experiments indicate the length of each edge to be approximately 6.8 nm. 

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