Sol-gel chemistry of transition metal oxides

Tetrathiafulvalenes, oligoacenenes, and their buckminsterfullerene derivatives: the brick and mortar of organic electronics.

Structural Aspects of Aromaticity

!Received 19 December 2005; accepted 27 January 2006 "The deÞnitions for important Rietveld error indices are deÞned and discussed. It is shown that whilesmaller error index values indicate a better Þt of a model to the data, wrong models with poor qualitydata may exhibit smaller values error index values than some superb models with very high qualitydata. © 2006 International Centr e for Diffraction Data. #DOI: 10.1 154/1.2179804 $

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R factors in Rietveld analysis: How good is good enough?

Since their first detection and bulk production, the fullerenes have
gained a primary role on the scientific scene, reaching their climax when
the 1996 Nobel Prize for Chemistry was awarded to Kroto, Curl and Smalley
for their seminal discovery. The unique physical and chemical properties
of these new forms of carbon led many scientists to predict several
technological applications. This created a heavy disappointment when it
was clear that fullerene-based materials would not soon be ready for the
market. However, the fullerenes have so far delighted several dozens of
researchers who found that C
 60
 and its relatives undergo a
variety of chemical reactions. In most cases, the new derivatives retain
the main properties of the original fullerene, and it is now not unlikely
that some functionalized fullerenes may find useful applications in the
field of materials science and technology. In this Article we summarize
the basic principles of the organic chemistry of fullerenes, together with
a description of the physicochemical properties that have made these
carbon cages popular in materials science, and review the most recent
achievements in the functionalization of fullerenes aimed at the
production of new molecular materials.

[60]Fullerene chemistry for materials science applications

The Structure of C60: Orientational Disorder in the Low‐Temperature Modification of C60

Methods, implemented into a computer program (LSABS), are described which calculate transmission factors and their first derivatives with respect to the positions of the faces of a convex polyhedral monocrystal. Both Gaussian and analytical integration procedures are considered in detail. LSABS has been implemented as a module of the Xtal system of programs. It functions independently of the instrument used to collect the intensity data. Test results obtained with this program are compared with standard literature values. Correlation coefficients of an absorption-corrected intensity data set of calcite, CaCO3 are reported. The need for transmission factor derivatives in the refinement of crystal shape and in the elimination of correlated absorption-corrected structure amplitudes is explained.

The evaluation of transmission factors and their first derivatives with respect to crystal shape parameters

A Topochemically Controlled, Regiospecific Fullerene Bisfunctionalization

Structure of a chelated dinuclear peroxytitanium(IV)

The electron-density distributions in the pyrite-type structures of CoS2 and NiS2 have been determined from high-resolution single-crystal diffraction data [Ag Ka radiation; resolution and temperature (sin0/A)max = 1"49 /~-I at 295 K for COS2, 1.63 ~-1 at 135 K for NiS2]. The charge densities were refined using a multipolar deformation model [R(IFI) = 0.0119 and 0.0136, respectively]. The X-ray diffraction data of FeS2 [Stevens, DeLucia & Coppens (1980). lnorg. Chem. 19, 813-820; Ag Ka radiation, (sin0/a)m.x = 1.46 A-i, room temperature] were refined using the same deformation model and program in order to facilitate comparison of the results [R(IFI) = 0.0176]. The main features of the resulting deformation maps agree well for all three structures. They consist of important maxima in the immediate vicinity of the metal atoms pointing towards the faces of the coordination octahedron. The heavier the metal atom, the smaller is the distance of the maxima from the atomic centre. These features are interpreted by a preferential occupation of the metal d orbitals which correspond to the cubic t2e orbitals. An analysis of the d-orbital populations indicates that the symmetry of the electron distribution around the metal atom is in all cases very close to cubic, the site symmetry being 3; the t2g orbitals appear to be fully occupied by six electrons while the occupation of the eg orbitals increases in the series Fe, Co, Ni and indicates covalent overlap with the S ligands.

Dieter Schwarzenbach

Papers

The Structure of C60: Orientational Disorder in the Low‐Temperature Modification of C60

The evaluation of transmission factors and their first derivatives with respect to crystal shape parameters

A Topochemically Controlled, Regiospecific Fullerene Bisfunctionalization

Structure of a chelated dinuclear peroxytitanium(IV)

Charge densities in CoS2 and NiS2 (pyrite structure)