Cubane. structural properties

Use of the tripodal ligand Saltren creates a tetranuclear complex [Mn402(Sal-tren)2][MnCl4] 2CH3CN (172) having a fused open cubane structure without a carboxylate group. At 300 K the value of the effective magnetic moment for (172) is 5.1 /Ub, which decreases to 2.0 /iB at 4.2 K. The redox properties of (172) in propylene carbonate have been studied by cyclic voltammetry. Two oxidation responses are observed at = —0.32V and 0.43 V vs. SCE. 

One of the most significant discoveries in Fe-S biochemistry in the last decade has been that of [3Fe-4S] clusters. Beinert and Thomson (114) have summarized the early work leading to the recognition of these clusters. This work has culminated in the proof by protein crystallography of the voided-cubane structure 3 (Fig. 1) for clusters in Azotobacter vinelandii (/4v) Fd I (which also contains one [4Fe-4S] cluster) (11, 13, 14), Desul-fovibrio gigas (Dg) Fd II (12, 15), and aconitase from pig heart (115). In these clusters, Fe-Fe separations occur in the range 2.M-2.77 A. As will be seen, aconitase and Dg Fd II assume particular significance in the context of site-specific properties. 

Structural data of the cuboidal model compound and of protein sites indicate that the cuboidal cluster is structurally closely related to the cubane cluster and shares many of the same structural properties. 

The cubane structure [Fe4S4(SR)4] shown below is a synthetic analogue of a common cofactor found in many enzymes. The structure can undergo a reversible one-electron reduction to [Fe4S4(SR)4] . What basis set and level of theory would be needed to model the geometries of both compounds accurately Draw up a list of all the properties of this system that could be calculated using the computational methods discussed in this chapter. 

The remarkable structural properties of cubane greatly motivate us to investigate its underlying driving force. We employ an ab initio method to calculate its bond structure for a pure cubane. All the calculations are performed at the Hartree-Fock level by the Molpro package [9]. The basis set used for hydrogen is (4S 1 P)/[2S 1P], whereas for carbon (9S 4P 1D)/[3S 2P ID] is used. The basis functions are all valence triple zeta correlated basis sets. 

T. Yildirim et al., First-principles investigation of structural and electronic properties of solid cubane and its doped derivatives. Phys. Rev. B 62, 7625 (2000)... 

The polycyclic cage compounds of Group 14 elements heavier than carbon (i.e. tetrahedranes, cubanes, prismanes, etc.) have fascinated chemists for a long time because of their unique structures and expected unusual physico-chemical properties and reactivity1. It was quite reasonable to assume that such exotic compounds could possess properties... 

Kalinina IV, Fedin VP. Cubane chalcogenide complexes of group IV-VI metals Synthesis, structure, and properties. Russ J Coord Chem 2003 29 597-615. 

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