The effect of pressure on clusters, chains and single-molecule magnets

This research deals with the investigation of the correlation between the structures of molecules and their magnetic properties as a function of pressure. To do so, different kinds of molecules have been chosen from single-molecules magnets, chains to small molecules. The variety of molecules is necessary to find the best candidates for high pressure X-ray crystallography and high pressure magnetic measurements. Bonds lengths and angles have been successfully altered by using high pressure without the complicating issues of chemical modifications. These structural changes produced a significant effect on the magnetic properties. A tilting of the Jahn-Teller axis in [Mn12O12(O2CCH2tBu)16(H2O)4].MeNO2.CH2Cl2 has been observed both structurally and magnetically. Modification of π–π interactions from edge to edge interaction to offset π–π stacking in [Gd(PhCOO)3(DMF)]n or a conversion from a CH–π interaction to a π–π interaction in [N(PhCH2)(CH2CH3)3]2[Fe2OCl6] are also reported

catena-Poly[[bis­(ethyl­enediamine)copper(II)]-μ-sulfato]

In the title compound, [Cu(SO4)(C2H8N2)2]n, the Cu, S and two O atoms lie on a mirror plane. The Cu atom is in a distorted octa­hedral environment and the ethyl­enediamine ligand is in a gauche conformation. The sulfate dianion is bridging, forming a one-dimensional chain. A two-dimensional net parallel to (001) is generated by N—H⋯O hydrogen bonding between the chains

Vallés obrero : plataforma de CCOO de empresa del Vallès Oriental

BACKGROUND: The size and complexity of molecules being studied by single crystal diffraction is growing year by year, resulting in an increase in the difficulties encountered during structure determination. From the crystallisation itself and sample handling, to structure solution and refinement, specific problems due to larger molecules are discussed. RESULTS: During refinement, several methods are available to deal with the problems encountered with large structures within the software Crystals. Hydrogens atoms can neither be found easily nor refined freely, but restraints can be applied automatically. Special scattering factors can be used to model complex disorder. Finally chemical information can be included in the form of restraints in order to help the determination of a good model. Multicollinearity problems are more likely in the refinement of large structures; to some extent more precise and accurate algorithms can help. Also, if the global minimum is less well defined, faster refinement enables more cycles to be carried out, a necessity for good convergence. The efficiency of the algorithms in Crystals have been increased to help address these issues. CONCLUSIONS: Thus, crystal structures are getting larger and their complexity is increasing. Recent developments in precision and speed during the least squares in Crystals is helping the structural scientist to deal with larger structures more efficiently

XPAD X-ray hybrid pixel detector for charge density quality diffracted intensities on laboratory equipment

International audienceThe new generation of X-ray detectors, the hybrid pixel area detectors or `pixel detectors', is based on direct detection and single-photon counting processes. A large linearity range, high dynamic and extremely low noise leading to an unprecedented high signal-to-noise ratio, fast readout time (high frame rates) and an electronic shutter are among their intrinsic characteristics which render them very attractive. First used on synchrotron beamlines, these detectors are also promising in the laboratory, in particular for pump-probe or quasi-static experiments and accurate electron density measurements, as explained in this paper. An original laboratory diffractometer made from a Nonius Mach3 goniometer equipped with an Incoatec Mo microsource and an XPAD pixel area detector has been developed at the CRM2 laboratory. Mo K alpha accurate charge density quality data up to 1.21 angstrom(-1) resolution have been collected on a sodium nitroprusside crystal using this home-made diffractometer. Data quality for charge density analysis based on multipolar modelling are discussed in this paper. Deformation electron densities are compared to those already published (based on data collected with CCDAPEXII and CAD4 diffractometers)

In-house time-resolved photocrystallography on the millisecond timescale using a gated X-ray hybrid pixel area detector

International audienceWith the remarkable progress of accelerator-based X-ray sources in terms of intensity and brightness, the investigation of structural dynamics from time-resolved X-ray diffraction methods is becoming widespread in chemistry, biochemistry and materials science applications. Diffraction patterns can now be measured down to the femtosecond timescale using X-ray free electron lasers or table-top laser plasma X-ray sources. On the other hand, the recent developments in photon counting X-ray area detectors offer new opportunities for time-resolved crystallography. Taking advantage of the fast read-out, the internal stacking of recorded images, and the gating possibilities (electronic shutter) of the XPAD hybrid pixel detector, we implemented a laboratory X-ray diffractometer for time-resolved single-crystal X-ray diffraction after pulsed laser excitation, combined with transient optical absorption measurement. The experimental method and instrumental setup are described in detail, and validated using the photoinduced nitrosyl linkage isomerism of sodium nitroprusside, Na 2 [Fe(CN) 5 NO]Á2H 2 O, as proof of principle. Light-induced Bragg intensity relative variations ÁI(hkl)/I(hkl) of the order of 1%, due to the photoswitching of the NO ligand, could be detected with a 6 ms acquisition window. The capabilities of such a laboratory time-resolved experiment are critically evaluated

CCDC 768038: Experimental Crystal Structure Determination

An entry from the Cambridge Structural Database, the world’s repository for small molecule crystal structures. The entry contains experimental data from a crystal diffraction study. The deposited dataset for this entry is freely available from the CCDC and typically includes 3D coordinates, cell parameters, space group, experimental conditions and quality measures

CCDC 768044: Experimental Crystal Structure Determination

An entry from the Cambridge Structural Database, the world’s repository for small molecule crystal structures. The entry contains experimental data from a crystal diffraction study. The deposited dataset for this entry is freely available from the CCDC and typically includes 3D coordinates, cell parameters, space group, experimental conditions and quality measures

CCDC 768040: Experimental Crystal Structure Determination

An entry from the Cambridge Structural Database, the world’s repository for small molecule crystal structures. The entry contains experimental data from a crystal diffraction study. The deposited dataset for this entry is freely available from the CCDC and typically includes 3D coordinates, cell parameters, space group, experimental conditions and quality measures

CCDC 768042: Experimental Crystal Structure Determination

An entry from the Cambridge Structural Database, the world’s repository for small molecule crystal structures. The entry contains experimental data from a crystal diffraction study. The deposited dataset for this entry is freely available from the CCDC and typically includes 3D coordinates, cell parameters, space group, experimental conditions and quality measures