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A synchrotron radiation fiber diffraction structural study of the axial filament of siliceous spicules from two species of marine sponges (the Demosponge Geodia cydonium and the Hexactinellid Scolymastra joubini) was carried out. The sharpness of the spots in the diffraction patterns indicated that the protein units in the filament of both samples were highly organized. A possible explanation is that the arrangement of the protein units is similar to that of the pores in highly ordered siliceous mesoporous materials. Nevertheless, the diffraction patterns are quite different for the two types of spicules. The pattern of G. cydonium is consistent with a regular 2D hexagonal lattice of protein units in the direction perpendicular to the spicule axis, with a repeating distance of 5.8 nm; the units are linked to form fibers along the axis. The pattern of S. joubini indicates the presence of two different 2D lattices in which the repeating protein units are inclined by +50 degrees and -50 degrees with respect to the elongation axis; the distance between the units increases to 8.4 nm. This 2D model is consistent with hexagonal packing of spirally oriented cylindrical protein units elongated along the filament axis., (Copyright 2003 Wiley-Liss, Inc.)

A model photosensitizer (D5) for application in dye-sensitized solar cells has been studied by a combination of XRD, theoretical calculations, and spectroscopic/chemometric methods. The conformational stability and flexibility of D5 and molecular interactions between adjacent molecules were characterized to obtain the driving forces that govern D5 uptake and grafting and to infer the most likely arrangement of the molecules on the surface of TiO2. A spectroscopic/chemometric approach was then used to yield information about the correlations between three variables that govern the uptake itself: D5 concentration, dispersant (chenodeoxycholic acid; CDCA) concentration, and contact time. The obtained regression model shows that large uptakes can be obtained at high D5 concentrations in the presence of CDCA with a long contact time, or in absence of CDCA if the contact time is short, which suggests how dye uptake and photovoltaic device preparation can be optimized. [ABSTRACT FROM AUTHOR]

This paper describes a new method for extracting the individual contributions to the diffracted intensity of subsets of atoms in the crystal structure. The periodic perturbation of the scattering process, required for untangling the scattered intensity, is provided by altering the resonant contributions. The theory of modulation enhanced diffraction (MED) is briefly recalled in the context of resonant scattering. A periodic variation in the atomic form factor has been achieved by changing the X-ray energy in such a way that the MED theory holds. Simulated results and experimental data are presented, together with necessary corrections. Two data analysis schemes are presented, both illustrating the advantages and drawbacks of the novel modulation technique. [ABSTRACT FROM AUTHOR]

The article presents a study which develops a theory to identify the kinematic diffraction response to a periodic perturbation of a crystal. It shows that the diffracted signal doubles the function of the stimulation frequency when a part of a local electron density varies linearly with an external stimulus. It discusses two ways of filtering, demodulation and correlation, with respect to extracting information from the experiment.

X-ray powder diffraction played a key role in materials science over the past 25 years. It is now possible to employ powder diffraction at in situ conditions to study solid-state transformations. “Real” materials science samples often show deviations from the “perfectly crystalline” state and hence powder diffraction reaches its limits. Spectroscopic techniques can often provide useful complementary information. With the aim of gaining information from this aspect, we combined Raman spectroscopy with diffraction. A novel experimental setup for simultaneous in situ Raman and XRPD experiments was designed and realized at the SNBL line at ESRF Synchrotron (Grenoble-F). High-resolution XRPD data can be collected with a time resolution in the range of minutes. A permanently installed Raman spectrometer can now be used to measure the same sample at the same spot under the same conditions. A wide variety of non-ambient conditions are available. The setup is described with limitations and potentialities, by describing one example of application. Finally some hints on future improvements are described. [ABSTRACT FROM AUTHOR]

Materials containing disordered moieties and/or amorphous or liquid-like phases or showing surface- or defect-related phenomena constitute a problem with respect to their characterization using X-ray powder diffraction (XRPD), and in many cases Raman spectroscopy can provide useful complementary information. A novel experimental setup has been designed and realized for simultaneous in situ Raman/high-resolution XRPD experiments, to take full advantage of the complementarities of the two techniques in investigating solid-state transformations under non-ambient conditions. The added value of the proposed experiment is the perfect synchronization of the two probes with the reaction coordinate and the elimination of possible bias caused by different sample holders and conditioning modes used in ` in situ but separate' approaches. The setup was tested on three solid-state transformations: (i) the kinetics of the fluorene–TCNQ solid-state synthesis, (ii) the thermal swelling and degradation of stearate–hydrotalcite, and (iii) the photoinduced (2 + 2)-cyclization of ( E)-furylidenoxindole. These experiments demonstrated that, even though the simultaneous Raman/XRPD experiment is more challenging than separate procedures, high-resolution XRPD and Raman data can be collected. A gas blower allows studies from room temperature to 700 K, and 100 K can be reached using a nitrogen cryostream. The flexibility of the experimental setup allows the addition of ancillary devices, such as a UV lamp used to study photoreactivity. [ABSTRACT FROM AUTHOR]

Abstract: The structure of the [Os(bpy)2(CO)Cl]+Otf– complex (where bpy=2,2′-bipyridine and Otf– =triflate, CF3SO3 –) has been solved by single crystal X-ray diffraction analysis and the NMR technique has been employed for the characterization of the complex in solution. Theoretical calculations have been performed to unravel the structural disorder found in the solid state and for the characterization of the geometric and energetic features of the complex in apolar solution. This study is part of our investigation of Os(bpy)2(CO) complexes and in this paper we also intend to investigate the effect of different anions on the solid and solution properties of the [Os(bpy)2(CO)Cl]+ cation. To cite this article: G. Croce et al., C. R. Chimie 8 (2005) . [Copyright &y& Elsevier]

The high X-ray flux available at the European Synchrotron Radiation Facility (ESRF), combined with the use of a suitably designed area detector setup, allowed us to follow in real time the structural changes occurring during the template burning processes inside TS-1 and Fe-silicalite MFI zeolites with a X-ray powder diffraction technique (XRPD). Rietveld analysis of the XRPD patterns collected in the 350-1000 K interval, integrated each 15 K, yields to the determination of the template overall occupancy factor versus T with an accuracy comparable with that obtained by thermogravimetric measurements, routinely employed for this purpose. The evolution of the structural parameters (V, a, b, c, site occupancy factor of the template molecule) vs T has been obtained. These data allow us to have, for the first time, a complete view of the structural rearrangements induced by the template burning process on the zeolitic framework. The differences caused by the different heteroatom inserted in the MR lattice (Ti or Fe) are discussed. For both TS-1 and Fe-MFI, the kinetics of the reaction were investigated, to obtain the activation energy of the calcinations process employing the nonisothermal data according to the theory recently proposed by Kennedy and Clark [Thermochim. Acta, 1997, 307, 27-35]. For TS-1 only, the time-resolved template burning experiment has been repeated in isothermal conditions at four different temperatures, to obtain the activation energy from isothermal data, according to the standard procedure. Comparison between Arrhenius plots obtained from isothermal and nonisothermal data demonstrates that the Kennedy and Clark method can be also applied to complex materials such as the MFI zeolites. This approach, when applied to time-resolved XRPD studies, is much less time consuming (requesting, in principle, one single nonisothermal run) with respect to the classic approach, which requests at least three isothermal runs. Moreover, it allows a remarkably lower associated error (151 ±11 versus 146 ± 30 kJ mol[sup-1]) due to the much higher number of experimental points employed to perform the linear fit. [ABSTRACT FROM AUTHOR]

Multivariate analysis (MA) is becoming a fundamental tool for processing in an efficient way the large amount of data collected in X-ray diffraction experiments. Multi-wedge data collections can increase the data quality in case of tiny protein crystals; in situ or operando setups allow investigating changes on powder samples occurring during repeated fast measurements; pump and probe experiments at X-ray free-electron laser (XFEL) sources supply structural characterization of fast photo-excitation processes. In all these cases, MA can facilitate the extraction of relevant information hidden in data, disclosing the possibility of automatic data processing even in absence of a priori structural knowledge. MA methods recently used in the field of X-ray diffraction are here reviewed and described, giving hints about theoretical background and possible applications. The use of MA in the framework of the modulated enhanced diffraction technique is described in detail. [ABSTRACT FROM AUTHOR]

Low-ordered carbon/layered double hydroxide (LDH) nanocomposites were prepared by rehydration of the oxides produced by calcination of an organic LDH. While the memory effect is a widely recognized effect on oxides produced by inorganic LDH, it is unprecedented from the calcination/rehydration of organic ones. Different temperatures (400, 600, and 1100 °C) were tested on the basis of thermogravimetric data. Water, instead of a carbonate solution, was used for the rehydration, with CO2 available from water itself and/or air to induce a slower process with an easier and better intercalation of the carbonaceous species. The samples were characterized by X-ray powder diffraction (XRPD), infrared in reflection mode (IR), and Raman spectroscopies and scanning electron microscopy (SEM). XRPD indicated the presence of carbonate LDH, and of residuals of unreacted oxides. IR confirmed that the prevailing anion is carbonate, coming from the water used for the rehydration and/or air. Raman data indicated the presence of low-ordered carbonaceous species moieties and SEM and XRPD the absence of separated bulky graphitic sheets, suggesting an intimate mixing of the low ordered carbonaceous phase with reconstructed LDH. Organic LDH gave better memory effect after calcination at 400 °C. Conversely, the carbonaceous species are observed after rehydration of the sample calcined at 600 °C with a reduced memory effect, demonstrating the interference of the carbonaceous phase with LDH reconstruction and the bonding with LDH layers to form a low-ordered carbon/LDH nanocomposite. [ABSTRACT FROM AUTHOR]

The article discusses the highlights of a workshop on the investigation of solid-state transformations and reactions at non-ambient conditions using simultaneous Raman-X-ray diffraction and absorption, held by the Swiss-Norwegian Beam Lines (SNBL) from June 18 to 19, 2008 in France. The use of such techniques in various studies in the fields of materials science, geophysics, sold state chemistry, among others, was demonstrated. Several of these studies were complex and carried under external stimuli so as to reproduce experiments on individual machines.

The Inside Cover picture underlines the link between solar energy and a sustainable economy. The sunny sky represents the environment in which we live and the dye‐sensitized solar cell one of the tesserae needed to build the puzzle of a sustainable future. The optimization of DSC modules is facilitated through the chemical sciences represented by the molecule of D5, the topic of the paper, and through a deep comprehension of the molecular mechanism, represented by the 3D energetic landscape obtained by a combination of theoretical and experimental techniques. More details can be found in the Full Paper by Gianotti et al. on page 3039 (DOI: 10.1002/cssc.201402194). [ABSTRACT FROM AUTHOR]

Abstract: We report a combined experimental and computational study of new rhenium tricarbonyl complexes based on the bidentate heterocyclic N–N ligands 2-(4-methylpyridin-2-yl)benzo[d]-X-azole (X=N–CH3, O, or S) and 2-(benzo[d]-X-azol-2-yl)-4-methylquinoline (X=N–CH3, O, or S). Two sets of complexes are reported. Chloro complexes, described by the general formula Re(CO)3[2-(4-methylpyridin-2-yl)benzo[d]-X-azole]Cl (X=N–CH3, 1; X=O, 2; X=S, 3) and Re(CO)3[2-(benzo[d]-X-azol-2-yl)-4-methylquinoline]Cl (X=N–CH3, 4; X=O, 5; X=S, 6) were synthesized heating at reflux Re(CO)5Cl with the appropriate N–N ligand in toluene. The corresponding pyridine set {Re(CO)3[2-(4-methylpyridin-2-yl)benzo-X-azole]py}PF6 (X=N–CH3, 7; X=O, 8; X=S, 9) and {Re(CO)3[2-(benzo[d]-X-azol-2-yl)-4-methylquinoline]py}PF6 (X=N–CH3, 10; X=O, 11; X=S, 12) was synthesized by halide abstraction with silver nitrate of 1–6 followed by heating in pyridine and isolated as their hexafluorophosphate salts. All complexes have been fully characterized by IR, NMR, electrochemical techniques and luminescence. The crystal structures of 1 and 7 were obtained by X-ray diffraction. DFT and time-dependent (TD) DFT calculations were carried out for investigating the effect of the organic ligand on the optical properties and electronic structure of the reported complexes. [Copyright &y& Elsevier]