Synchrotron X-rays are very suitable for advanced crystal structure analysis in material science. In fact, many scientists carry out various experiments in order to understand physical and functional property. Extremely, charge density study, submicron single crystal diffractometry, operand structural study of single crystal and poly-crystals, and time-resolved experiments have been actively engaged in research on the structure analysis in order to elucidate the association between functional properties and crystalline structures. Here, I report current research and future outlook of structure analysis using synchrotron X-rays.
Even though the single crystal neutron diffraction technique is one of the most powerful methods to observe hydrogen atoms in molecular crystals, the necessity of a large single crystal has been a serious bottle-neck of this technique. Recently, author and co-workers constructed a new TOF-Laue single crystal neutron diffractometer, SENJU, at J-PARC/MLF. Neutron structure analysis of a 0.1 mm3 taurine single crystal by using SENJU showed that single crystal neutron structure analysis of a sub-millimeter size molecular crystal is feasible in realistic beam-time. In addition, diffraction measurement of a small crystal with 4 K cryostat and other sample environment devices at SENJU will make several types of “theoretically possible” experiments in the field of crystal chemistry, such as observation of metastable species or visualization of spin electron density by neutron diffraction, “practically possible”.
The methods for ab initio crystal structure analysis from powder data have been highly-evolved for these 20−30 years. Recently many people can use the technique thanks to some software packages for the powder structure analysis such as EXPO, even if they are non-professional users. In such packages, there are new good tools which do not seem to be very popular. Here such the new, useful methods, which will make your analysis a success more often, are described.
Multipole expansion method is frequently used for refinements on electron density distribution of organic compound and metal complex crystals aiming at understanding nature of chemical bonds and intra- and inter-molecular interactions. In this article, short introduction of the method, and procedures on experiments and refinements are presented. Electron density distribution analysis of a singlet biradical compound generated in C-P-C-P four-membered ring is also presented. Topological analysis based on Atoms in Molecules theory is performed.
Chocolate consists of solid particles such as cocoa, sugar, and milk solids which are dispersed in a continuous fat phase. The major fat in chocolate is cocoa butter, and it is crystallized at room temperature, so chocolate is a food which we eat crystals. Therefore, fat crystals play a great role in chocolate quality and storage stability. In this paper, polymorphism of cocoa butter and the transformation of polymorphic forms are reviewed including recent results.
In this review, we report isolation of unstable tri-sulfur, S3, in a porous coordination network which is used as a crystalline molecular flask. The ozone-like structure of S3 in a pore was determined by ab initio X-ray powder diffraction analysis. The S3 in the pore was interacted with iodine which faces to the pore of the network. The S3 in the network was quite stable unlike unstable gaseous S3 molecule because of the S-I interaction in the pore. Furthermore, the S3 in the network could be transformed to S6 by mechanical grinding or heating in the presence of NH4Cl. We will introduce new chemistry of small sulfur based on crystal structure.
In this review, we report recent nuclear resonance vibrational spectroscopic (NRVS) studies of iron-containing biomolecules and their model complexes. The NRVS is synchrotron-based element-specific vibrational spectroscopic methods. Unlike Raman and infrared spectroscopy, the NRVS can investigate all iron motions without selection rules, which provide atomic level insights into the structure/reactivity correlation of biologically relevant iron complexes.