Clusters crystal structure

Cluster Crystal structure Method of preparation Refs. 

Enormous expansion has happened in the field of nanoclusters and researchers have shown an effective role of mass spectrometry in characterizing such pieces of matter. It is important to mention here that mass spectrometiy is not the only tool to characterize such clusters. Crystal structure is veiy much important to understand the detailed structure. Although there are plenty of reports of clusters assigned through mass spectrometry, only a few of them have been crystallized. A brief discussion of the clusters ctystallized is given in Table 1. In general, the structures consist of a metallic core which are surrounded by... 

The usual chemical and spectroscopic techniques such as elemental analyses, molecular weight determinations, and infrared, NMR, and electronic spectroscopy, are frequently useful for the characterization of transition metal cluster compounds. However, x-ray crystallography and, to a lesser extent, mass spectrometry, are almost indispensable for the unambiguous identification of new metal cluster systems. Indeed, much of the rapid progress in metal cluster chemistry since the appearance of Cotton s review article in 1965 (98) can be attributed to the widespread availability of automated x-ray-diffraction equipment. This increases significantly the number and accuracy of crystal structures that can be determined with a given amount of manpower, and thus the analyses of a great many more new metal cluster crystal structures are completed each year. 

Dimolybdenum complexes with sulfide and thiolate ligands as precursors to mixed-metal clusters crystal structure of [Mo2Ru2(,U3-S)2( U-SPr )2(CO)4(77-C5H5)2], H. Adams, N. A. Bailey, S. R. Gay, L. J. Gill, T. Hamilton, and M. J. Morris, J. Chem. Soc. Dalton Trans., 1996, 12, 2403. 

Syntheses, crystallization, structural identification, and chemical characterization of high nuclearity clusters can be exceedingly difficult. Usually, several different clusters are formed in any given synthetic procedure, and each compound must be extracted and identified. The problem may be compounded by the instabiUty of a particular molecule. In 1962 the stmcture of the first high nuclearity carbide complex formulated as Fe (CO) C [11087-47-1] was characterized (40,41) see stmcture (12). This complex was originally prepared in an extremely low yield of 0.5%. This molecule was the first carbide complex isolated and became the foremnner of a whole family of carbide complexes of square pyramidal stmcture and a total of 74-valence electrons (see also Carbides, survey). 

Marmorstein, R., Harrison, S.C. Crystal structure of a PPRl-DNA complex DNA recognition by proteins containing a Zn2Cys6 binuclear cluster. Genes Dev. 

The structure and bonding in lithium methyl have been particularly fully studied. The crystal structure consists of interconnected tetrameric units (LiMe)4 as shown in Fig. 4.17 the individual Li4C4 clusters consist of a tetrahedron... 

In this paper, the electronic structure of disordered Cu-Zn alloys are studied by calculations on models with Cu and Zn atoms distributed randomly on the sites of fee and bcc lattices. Concentrations of 10%, 25%, 50%, 75%, and 90% are used. The lattice spacings are the same for all the bcc models, 5.5 Bohr radii, and for all the fee models, 6.9 Bohr radii. With these lattice constants, the atomic volumes of the atoms are essentially the same in the two different crystal structures. Most of the bcc models contain 432 atoms and the fee models contain 500 atoms. These clusters are periodically reproduced to fill all space. Some of these calculations have been described previously. The test that is used to demonstrate that these clusters are large enough to be self-averaging is to repeat selected calculations with models that have the same concentration but a completely different arrangement of Cu and Zn atoms. We found differences that are quite small, and will be specified below in the discussions of specific properties. 

In Section 4.5, we discuss the optical properties of clusters formed by sexi-thienyl molecules adopting the herringbone structure characteristic of their crystal structure [34]. The theoretical results arc compared to corresponding experimental measurements. 

Figure 6-5. Excitation cncigics horn the ground stale to the two Davydov eoinponents (a and b ) as a function of die Th duster si/.e. The clusters are built with the crystal structure considering T(1 molecules lying within the same be layer.

X-ray absorption spectroscopy has been performed on the isolated Rieske protein from bovine heart mitochondrial bc complex 69) as well as on the Rieske-type cluster in Burkholderia cepacia phthalate dioxygenase (PDO) (72). The analysis performed by Powers et al. 69) was significantly hampered by the fact that the presence of two histidine ligands was not fully recognized therefore, only the results obtained with the dioxygenase where the mononuclear iron has been depleted will be considered here. Table VII gives a comparison of the distances obtained from the fit of the EXAFS spectra assuming an idealized Rieske model and of the distances in the crystal structures... 

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