Silicate materials have been proposed as alternative cathodes for Li-ion battery applications. A novel mixture of silicates, labelled Li6MnSi5, based on the molar ratio among the Li / Mn / Si precursors, with promising electrochemical properties as positive electrode material is synthesized through a solid-state reaction. The results indicate the proposed synthetic method as effective for preparation of nanostructured silicate owders with average particle diameter of 30 nm. Structural morphology of the samples was determined using X-ray powder diffraction (XRPD), XPS and FESEM analysis. A joint analysis by XRPD data and by density unctional theory (DFT) identified LiHMn4Si5O15, Li2Mn4Si5O15, Li2Si2O5 and Li0.125Mn0.875SiO4 as components of Li6MnSi5 mixture. The electrochemical performance of Li6MnSi5 was evaluated by charge/discharge testing at constant current mode. Li6MnSi5 discharge behaviour is characterized by high capacity value of 480 mA h g-1 , although such capacity fades gradually on cycling. Ex situ XPS studies carried out on the electrode in both full charged and discharged states, pointed out that Li2Si2O5 is decisive for achieving such high capacity. The discharge/charge plateau is most probably related to the change in the oxidation state of silicon at the surface of the silica material.

Ab initio crystal structure determination from powder diffraction data is not yet a straightforward process: it is strongly disrupted by the low quality of the estimated Bragg reflection intensities. In a two-stage method the integrated intensities calculated from a powder pattern are immediately submitted to direct methods to obtain phases. The larger the accuracy of the integrated intensities, the more efficient the phasing process. A systematic decomposition procedure was introduced in the EXPO2004 program to improve the efficiency of the phasing process. The disadvantage of this approach is that a large number of feasible trial structures are generated, among which the correct solution must be recognized. A new procedure is described aiming at introducing strategies to reduce the total number of trials to explore by defining an appropriate figure of merit able to regroup trial structures into different batches, each element of a batch sharing a high percentage of atoms with the other elements of the same batch. The new figure of merit, implemented in an updated version of EXPO2009, is able to discriminate non-solutions from promising trials, corresponding to incomplete or rough models which evolve, after refinement, into the correct solution.

The EXPO package [1] is a computing program able to successfullyprovide the structure solution by starting from minimal information:the experimental powder diffraction pattern and the chemical formulaof the compound to investigate. EXPO can be used for solving organic,inorganic, metalorganic structures for a large variety of applications.Automation and efficiency are suitably combined in EXPO forperforming all the steps of the solution process: indexation, spacegroup determination, intensity extraction, structure solution, modeloptimization, Rietveld refinement.Automation. Default strategies, identified as the most effective,are selected for carrying out the solution process automatically andquickly. They may fail when the experimental data resolution is badand/or the structure complexity is remarkable. In these cases, EXPOcan promptly switch to appropriate strategies by profiting by a userfriendly graphical interface.Efficiency. Innovative theories and computing procedures aimingat making straightforward all the steps of the solution process areintegrated in EXPO and widely tested. EXPO is continuously updatedand optimized in terms of both computing efficiency and graphicalperformances.In EXPO the two stages based ab initio approach (in the first stagethe intensities are extracted; in the second, the reflections are phasedby Direct Methods) [2] is the automatic choice. The model providedby Direct Methods is usually partial and approximate because of wellknown unavoidable problems in powder diffraction (overlapping,background, preferred orientation). It can be optimized by default [3],[4] and/or non-default strategies [5], [6] which are able to reduce theerrors depending on the limited experimental resolution.A very recent study has regarded a new and more effective figureof merit [7], alternative to the classical one. It is able to pick up thephasing trial corresponding to the best solution among several feasibleones.Non ab initio method, requesting the knowledge of the expectedmolecular geometry and based on Simulated Annealing technique[8, 9], can optionally be attempted particularly in case of solution oforganic compounds.Examples of successful automatic runs by EXPO will be discussedin addition to available special strategies.

A new procedure (COVMAP) has been developed with the aim of recovering the full structure from very poor models, such as those provided by direct methods in unfavorable conditions. The procedure is based on the concept of covariance between points of an electron density map, mathematically set out by the authors in a recent paper: i.e. the density at one point depends on the density at another point of the map if their covariance is not vanishing. This concept suggested a procedure of electron density modification that uses pairs of model peaks to restrict the region where the density modification should be applied. Such modified densities lead to additional peaks, which in turn are submitted to two other important phasing tools present in EXPO2011, the resolution bias minimization and weighted least-squares procedures, which relocate, refine or reject these peaks. The procedure is cyclic and often leads to the correct structure even if the starting model is very poor.

Quite recently two papers have been published [Giacovazzo & Mazzone (2011). Acta Cryst. A67, 210218; Giacovazzo et al. (2011). Acta Cryst. A67, 368382] which calculate the variance in any point of an electron-density map at any stage of the phasing process. The main aim of the papers was to associate a standard deviation to each pixel of the map, in order to obtain a better estimate of the map reliability. This paper deals with the covariance estimate between points of an electron-density map in any space group, centrosymmetric or non-centrosymmetric, no matter the correlation between the model and target structures. The aim is as follows: to verify if the electron density in one point of the map is amplified or depressed as an effect of the electron density in one or more other points of the map. High values of the covariances are usually connected with undesired features of the map. The phases are the primitive random variables of our probabilistic model; the covariance changes with the quality of the model and therefore with the quality of the phases. The conclusive formulas show that the covariance is also influenced by the Patterson map. Uncertainty on measurements may influence the covariance, particularly in the final stages of the structure refinement; a general formula is obtained taking into account both phase and measurement uncertainty, valid at any stage of the crystal structure solution.

The title compound, C24H25NO3·2CH3OH, which crystallized as a methanol disolvate, has applications as a PET radiotracer in the early diagnosis of Alzheimer's disease. The dihedral angle between the biphenyl rings is 8.2 (2)° and the heterocyclic ring adopts a half-chair conformation with the N atom adopting a pyramidal geometry (bond-angle sum = 327.6°). The C atoms of both meth­oxy groups lie close to the plane of their attached ring [deviations = 0.107 (6) and 0.031 (6) Å]. In the crystal, the components are linked by O-H...O and O-H...N hydrogen bonds, generating [010] chains. C-H...O inter­actions are also observed.

The COX-1 isoenzyme plays a significant role in a variety of diseases, as it catalyzes the bioprocesses behind many health problems. Among the diarylheterocycle class of COX inhibitors, the isoxazole ring has been widely used as a central heterocycle for the preparation of potent and selective COX-1 inhibitors such as P6 [3-(5-chlorofuran-2-yl)-5-methyl-4-phenylisoxazole]. The role of the isoxazole nucleus in COX-1 inhibitor selectivity has been clarified by preparing a set of new diarylheterocycles with various heterocycle cores. Replacement of isoxazole with isothiazole or pyrazole gave a drastic decrease in COX-1 inhibitory activity, whereas the introduction of an electron-donating group (EDG) on the N-aryl pyrazole allowed recovery of COX-1 inhibitory activity and selectivity. The EDG-equipped 5-(furan-2-yl)-1-(4-methoxyphenyl)-3-(trifluoromethyl)-1H-pyrazole (17) selectively inhibits COX-1 activity (IC50=3.4 mu M; 28?% COX-2 inhibition at 50 mu M), in contrast to its inactive analogue, 3-(furan-2-yl)-1-phenyl-5-(trifluoromethyl)-1H-pyrazole, which does not bear the methoxy EDG. Molecular docking studies of compound 17 into the binding site of COX-1 shed light on its binding mode.

Innovative methodologies, introduced in the software EXPO and working both in the reciprocal and in the direct space, can be successfully adopted for solving crystal structure by X-ray powder diffraction data. The principles underlying these methodologies are summarized. Three representative examples of crystal structure solution of the peptides Z-(Aib)(2)-OH, Z-(Aib)(3)-O-t-Bu and Z-(Aib)(4)-OH are discussed in relation to their different degree of structure complexity.

EXPO2011 is a new package for phasing crystal structures from powder diffraction diagrams. It is able to carry out all the steps necessary for crystal structure solution, from pattern indexation up to Rietveld method for structure refinement: for each step, the basic algorithm is described. Phasing is performed via ab initio (e.g., Direct Methods, integrated by real space refinement) and non ab initio techniques (e.g., simulated annealing algorithm, when molecular geometry is a priori known). Some emphasis is given to running procedures: the main commands and directives are described, to allow the user to run default and non-default phasing attempts.

EXPO2013, the heir of EXPO2009, has been enriched by a variety of new algorithms and graphical tools aiming at strengthening the individual steps of the powder structure solution pathway. Particular attention has been addressed to the procedures devoted to improving structural models provided by direct methods in ab initio approaches. In addition, a new procedure has been implemented, working in direct space, which may be chosen by the user as an alternative to the traditional simulated annealing algorithm. © 2013 International Union of Crystallography Printed in Singapore - all rights reserved.

This work demonstrates how the directing ability of the azetidine ring could be useful for regioselective ortho-C-H functionalization of aryl compounds. Robust polar organometallic (lithiated) intermediates are involved in this synthetic strategy. The reagent n-hexyllithium emerged as a safer, yet still effective, basic reagent for the hydrogen/lithium permutation relative to the widely used reagent nBuLi. Two different reaction protocols were discovered for regioselective lithiation at the ortho positions adjacent to the azetidine ring, which served as a toolbox when other competing directing groups were installed on the aromatic ring. The coordinating ability of the azetidine nitrogen atom, as well as the involvement of dynamic phenomena related to the preferential conformations of 2-arylazetidine derivatives, were recognized to be responsible for the observed reactivity and regioselectivity. A site-selective functionalization of the aromatic ring was achieved for aryl azetidines with either coordinatively competent groups (e.g. methoxy) or inductively electron-withdrawing substituents (e.g. chlorine and fluorine). By fine-tuning the reaction conditions, regioselective introduction of several substituents on the aromatic ring could be realized. Several substitution patterns were accomplished, which included 1,2,3-trisubstitution, 1,2,3,4-tetrasubstitution, and 1,2,3,4,5-pentasubstitution, up to the exhaustive substitution of the aromatic ring. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Negli ultimi venticinque anni il metodo della diffrazione da polveri è stato applicato con successo crescente per risolvere strutture cristalline (composti organici, inorganici, metallorganici). Nonostante ciò, la soluzione strutturale da polveri è ancora oggi una sfida perché i problemi del metodo, dovuti principalmente all'interpretazione dei dati sperimentali, devono essere ancora risolti.

The phase identification of a polycrystalline mixture by X-ray powder diffraction data is often requested for studying materials interesting to different scientific and technological fields: chemistry, pharmaceutics, mineralogy, archeometry, forensic science, etc. The availability of user friendly computer programs, able to carry out qualitative phase analysis in efficient and possibly automatic way, is extremely useful to the scientific community involved in powder diffraction. QUALX2.0, the evolution of QUALX, is a freely distributed software for qualitative phase analysis. Based on the traditional search-match method, it is able to manage both a commercial database (PDF-2 maintained by ICDD), and a freely available database (POW_COD generated by the structure information contained in the Crystallography Open Database). QUALX2.0 is continuously improved in terms of computing and graphic tools. Correspondingly, the database POW_COD is suitably modified to make efficient the operations of search. The search-match approach can be facilitated by the use of restraints, when available, involving the chemical composition, the kind of compound(s) (e.g., organic, inorganic, etc.), the symmetry (space group, crystal system), the unit-cell parameters and/or volume, the crystal properties (measured and/or calculated crystal density, crystal color). An outline of the main features of QUALX2.0 and an example of application is described.

Sixteen nephelines from different geological occurrences were sampled at the type-locality, the Somma-Vesuvius volcanic complex (southern Italy), and investigated for their chemistry and crystal structure obtained by both single-crystal and powder X-ray diffraction. Nepheline-bearing samples are metamorphic or from magmatic ejecta and pumice deposits. The lower K contents characterize the pumice- and some metamorphic-derived nephelines, whereas the higher ones are found in some samples from magmatic nodules. The amount of the anorthite molecule, quite low on average, can be more variable in the metamorphic nephelines. The crystal-structure investigations on Somma-Vesuvius samples compare well with previous studies of natural nephelines. All 16 nepheline samples adopt space group P63. The observed lattice parameters vary between 9.9768-9.9946 Å (for a) and 8.3614-8.3777 Å (for c), respectively. Furthermore, chemical analysis revealed that all specimens exhibit an excess of Si relative the ideal Si:Al ratio of 1:1. The analysis of the T-O distances in our samples clearly indicates a distinct ordering process of aluminium and silicon on the tetrahedral sites which is an agreement with Loewenstein's rule. A linear correlation between the distance of symmetry equivalent split atoms O(1)-O(1)' and the T(1)-O(1)-T(2) tilt angle was observed. The average <B-O> (B = Na) distances of all crystals are very similar which is consistent with the outcome of the site population refinement indicating full occupancy with sodium. Oriented precession-type sections of reciprocal space indicated the presence of at least the most intense family of satellite peaks, demonstrating that this group of satellite reflections can occur not only in nephelines from pegmatites and ijolites but also in rocks from completely different petrological settings.

Diastereomeric oxazolinylaziridines (R,R)-9 and (R,S)-9 have been regioselectively lithiated at the ?-position with respect to the oxazolinyl ring. The resulting aziridinyllithium compounds proved to be chemically and configurationally stable under the experimental conditions used, thus furnishing, upon trapping with electrophiles, chiral 2,2-disubstituted aziridines, in contrast to the corresponding ?-lithiated oxazolinyloxiranes that have been reported to be chemically stable but configurationally unstable. This peculiar behavior of the nitrogen-bearing heterocycle has been rationalized on the basis of DFT calculations and the observed dynamics of the aziridine nitrogen atom. The DFT analysis allowed the disclosure of a solvent-dependent differing stability of diastereomeric lithiated aziridines (R,R)-9-Li and (R,S)-9-Li, suggesting ?(3)-coordinated oxazolinylaziridinyllithium compounds as likely intermediates. Such intermediates could be the result of a dynamically controlled lithiation that relies on the preliminary formation of a complex between the lithiating agent and the oxazolinyl ring. According to this model, the competing complexation of the lithiating agent by the lone pair of electrons on the aziridine nitrogen would cause addition to the oxazoline C=N bond, thus ending up with the formation of oxazolidines, which are precursors of useful chiral ketoaziridines. The proposed model has been also supported by estimating the nitrogen inversion barrier by dynamic NMR spectroscopic experiments.

Rietveld refinement succeeds if the model is sufficiently close to the target structure. Severe distortions in the structural parameters or relatively high percentage of missed atoms do not allow the refinement to converge. Ab initio techniques like Direct or Patterson methods may rely only on the reflection intensities provided by full pattern decomposition algorithms. Owing to the relevant errors in the intensity estimates, the structural models provided by such phasing techniques are poor and require supplementary improvements before being submitted to Rietveld refinement. The situation is more favorable for non-ab initio techniques, when they can exploit the prior information on the full molecular geometry: their models can be easily submitted to Rietveld refinement, but often the accuracy of the refined model relies on the geometrical information rather than on the experiment. In this paper ab natio and non-ab initio phasing tools of EXPO2011, the updated and more powerful version of EXPO2009 [1], are described together with ancillary techniques for improving and completing the structural models.

QUALX2.0 is the new version of QUALX, a computer program for qualitative phase analysis by powder diffraction data. The previous version of QUALX was able to carry out phase identification by querying the PDF-2 commercial database. The main novelty of QUALX2.0 is the possibility of querying also a freely available database, POW_COD. POW_COD has been built up by starting from the structure information contained in the Crystallography Open Database (COD). The latter is a growing collection of diffraction data, freely downloadable from the web, corresponding to inorganic, metal-organic, organic and mineral structures. QUALX2.0 retains the main capabilities of the previous version: (a) automatically estimating and subtracting the background; (b) locating the experimental diffraction peaks; (c) searching the database for single-phase pattern(s) best matching to the experimental powder diffraction data; (d) taking into account suitable restraints in the search; (e) performing a semi-quantitative analysis; (f) enabling the change of default choices and strategies via a user-friendly graphic interface. The advances of QUALX2.0 with respect to QUALX include (i) a wider variety of types of importable ASCII file containing the experimental diffraction pattern and (ii) new search-match options. The program, written in Fortran and C++, runs on PCs under the Windows operating system. The POW_COD database is exported in SQLite3 format.

The new method RAMM (random-model-based method) has been developed and implemented in the EXPO computing program for improving the ab initio crystal structure solution process. When the available information consists of only the experimental powder diffraction pattern and the chemical formula of the compound under study, the classical structure solution approach follows two main steps: (1) phasing by direct methods (or by Patterson methods) in order to obtain a structure model (this last is usually incomplete and/or approximate); (2) improving the model by structure optimization techniques. This article proposes the alternative procedure RAMM, which skips step (1) and supplies a fully random model to step (2). This model is then submitted to effective structure optimization tools present in EXPO - wLSQ (weighted least squares), RBM (resolution bias minimization) and COVMAP (a procedure of electron density modification based on the concept of covariance between points of the map) - which are able to lead to the correct structure. RAMM is based on a cyclic process, generating several random models which are then optimized. The process stops automatically when it recognizes the correct structure.

This work is focused on the crystal-chemical characterization of the cationic and anionic components of sodalite-group minerals (SGM) occurring in various igneous-to-metamorphic rocks and ejecta from the alkaline-potassic Somma-Vesuvius volcano (southern Italy). A combination of different analytical techniques, i.e., XRD, SEM, EPMA, SIMS, FTIR, and mu-FTIR-FPA imaging, were used. Minor and trace volatile elements (H, C, and F) have been quantified for the first time (to the authors' knowledge) by SIMS, and in situ ion probe data were integrated with information derived from FTIR spectroscopy. The studied samples correspond to sodalite sensu stricto, nosean, and hauyne. SIMS measurements for H, F, and C (quantified as H2O, F, and CO2 wt.%, respectively) show contents 0.02-5.0 wt.% H2O, 0.01-0.14 wt.% F, and 0.08-2.95 wt.% CO2. Within the single crystals, the F and, to a lesser extent, CO2 concentrations are homogeneous, whereas, in terms of H2O, they range from relatively homogenous to strongly zoned. Single-crystal FTIR spectra of SGM can be grouped into sodalites and noseans/hauynes, according to the occurrence of the (CO2)-C-12 absorption at 2340 cm(-1). The absorption due to H2O or OH groups occurs as a very broad band extending from 3700 to 3000 cm(-1). FTIR data show the presence of CO32- in all samples. The collected data allow us to fully characterize the SGM from Somma-Vesuvius, and also provide some constraints regarding their genesis. These data can contribute to a more detailed understanding of the crystal chemistry of SGM, their geological environments of formation, and possibly of the technological characteristics of their synthetic analogues.

Aziridines are widely used as versatile building blocks for the synthesis of a variety of biologically and pharmaceutically importantmolecules [1]. Among the available methodologies for the preparation of functionalised aziridines, the lithiation/trapping sequence of simpleparent aziridines is growing in importance [2]. Present work reports the results concerning the structural study of aziridine-2-methanolderivatives by dynamic nuclear magnetic resonance (DMNR) [3] and single crystal X-ray diffraction. A careful examination of the aziridine2 (see figure 1) by NMR data, shows that at room temperature the meta protons and the protons of the two ortho methyl groups of the mesitylring gives featureless lumps, likely as consequence of a restricted rotation around the Csp3 -Csp2 bond between the carbinolic carbon andthe ipso carbon of the mesityl ring. Also in the solid state, an almost identical arrangement of the mesityl ring, with respect to the other twophenyl rings, has been observed. In this case, the aziridine nitrogen substituent was found in a syn relationship with respect to the carbinolicgroup so preventing the possibility of forming a hydrogen bond with the hydroxyl group. This evidence underlines a slow rotation of themesityl group instead of a nitrogen inversion as usually is expected. By X-ray analysis of 3 and diast-3 (figure 1), it is estimated that thenitrogen substituents set on the opposite side with respect the carbinolic carbon. Via study of crystal structures, the presence of hydrogenbonds between the hydroxyl group and the aziridine nitrogen lone pair was ascertained for aziridine 3 but not for diast-3 (figure 1). Such a hydrogen bond, which is persistent also in solution, could prevent the formation of conformational diastereoisomers by rotation around the bond between the carbinolic carbon and the aziridine quaternary carbon. This hypothesis has been demonstrated by NMR experiments. This investigation allowed us to calcolate some Csp2-Csp3 and Csp3-Csp3 rotational barriers and highlight a sort of "geared" rotation between aryl and alkyl substituents; this is possible if the structure is not in a locked conformation by an hydrogen bond as demonstrated by NMR and X-ray diffraction.

The 5-(5-nitro furan-2-ylmethylen), 3-N-(2-methoxy phenyl), 2-N'-(2-methoxyphenyl) imino thiazolidin-4-one compound has been synthesized and fully characterized by FT-IR, ¹H and ¹³C NMR spectroscopy. The crystal structure of the title compound was investigated by X-ray powder diffraction (XRPD). The obtained structure is triclinic, space group P-1, with a = 11.4746(3), b = 10.9106(2),c = 8.8083(2) Å, ? = 103.6665(9)°? = 91.4910(13)° ? = 84.1433(12)°, V = 1065.93(4)ų and Z = 2. The XRPD structural investigation has been completed by a theoretical analysis performed using the density functional theory (DFT) via a B3LYP functional at 6-311G(d,p) basis set. To highlight and establish the contribution of the different intermolecular interactions, Hirshfeld surface analysis and fingerprint plots were performed. The solid state molecular structure and packing are discussed.

A reciprocal-space resolution bias correction algorithm has been recently suggested, providing suitable corrections for the classical atomic scattering factors. The Fourier maps calculated by using as coefficients the structure factors obtained by the modified scattering factors proved to be less resolution biased. In this paper the correction has been generalized in order to apply it to the experimental structure factor moduli; in this way more useful electron density maps may be calculated. In a less recent paper a direct-space resolution bias correction algorithm was devised and tested on a large set of powder patterns; the algorithm implies the modification of the electron density maps to reduce the truncation errors in the Fourier syntheses. In the present paper direct and reciprocal resolution bias correction algorithms are combined into the dual-space resolution bias correction algorithm. The usefulness of the new algorithm is checked on a set of powder patterns.

The limited resolution of experimental diffraction data distorts the Fourier synthesis so that the electron density map obtained by the structure factors is an imperfect representation of the true density: the worse the experimental resolution, the less accurate the Fourier representation. We have recently developed new methods aiming at reducing the resolution effects by correcting it both in the Reciprocal Space (RS) and in the Direct Space (DS): e.g., by modifying the atomic scattering factors in RS and the electron density map in DS. The Dual-Space (DUS) method combines the RS and DS procedures. In addition, new computing strategies have been developed for improving the Fourier map calculation. The DUS algorithm has been introduced in the EXP02010 package in order to obtain more reliable structure models. It has been successfully applied to several test structures. The main features of the new procedure and the results of our applications will be described.

The big bang-big crunch method is a global optimization approach developed upon the analogy of one of the cosmological theories of the evolution of the universe. It has been suitably combined with a simulated annealing algorithm and used for solving crystal structure from powder diffraction data in direct space. When compared with the traditional simulated annealing method, it provides a significant advance: good solutions are attained in a shorter time. The new method has been implemented in the EXPO package. Its successful application is demonstrated with examples of already known structures.