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Low-temperature synchrotron X-ray diffraction and high-level density functional theory (DFT) calculations is evaluated to study the environmental influence on the electronic character of two O-H...O hydrogen bends in a beta-diketone, 2-acetyl-1,8-dihydroxy-3,6-dimethylnaphthalene. It is indicated that the electronic character of the short hydrogen bond cannot be attributed only to steric strain in the molecule.

The charge density of [Co.sub.2][(CO).sub.6](HC[triple bond]C[C.sub.6][H.sub.10]OH) in the crystalline state is determined by using multipolar refinement of single-crystal X-ray diffraction data. The results have shown that the topology of the experimental electron density in the special atomic environment is highly sensitive to subtle effects of measurement errors and potential shortcomings of the multipole model, or to effects of the crystal field.

The formation and growth of carbon(C)-supported platinum (Pt)nanoparticles in a high-temperature, high-pressure ethanol solutionhave been studied by in situ synchrotron radiation powder X-ray diffraction(PXRD). Supercritical synthesis is shown to be an efficient way toprepare Pt nanoparticles, and the crystallite size of Pt nanoparticlesis much smaller when formed with supporting C material compared withsynthesis without C. On the basis of the time-resolved in situ PXRDdata, a surface stress of 2.65 N/m is derived from the size dependenceof the cell parameters. As proof of concept, C-supported Pt nanoparticleswere subsequently synthesized in a pulsed-flow supercritical reactor,which offers complete control of the reaction temperature, pressure,and residence time. Well-dispersed Pt nanoparticles decorated on thesupporting C material can be obtained by adjusting the reaction conditions,and the electrocatalytic activity of the samples is explored. A massactivity of 0.1209 A/mgPtat a potential of 0.9 V is obtainedfor the products prepared at 400 °C for a residence time of 20s. The pulsed-flow supercritical method is a facile method to synthesizeligand-free C-supported Pt nanoparticles with high electrocatalyticactivity. [ABSTRACT FROM AUTHOR]

A 165 mm Mar CCD detector has been fitted on a large Huber four-circle diffractometer together with a helium cryostat at beamline D3 at Hasylab, DESY in Hamburg. This setup allows fast collection of accurate, shortwavelength, very low temperature X-ray diffraction data for charge-density analysis. As a test example, diffraction data have been collected in 10 h on a hydrogen-bonded network system with 15 unique atoms, and the electron density was modelled with the multipole formalism in an X-N procedure using matching-temperature neutron diffraction data collected at Institut Laue Langevin, Grenoble in France. [ABSTRACT FROM AUTHOR]

The crystal structure of the title compound, {[Eu2(C8H4O4)3(C5H11NO)2]·0.7H2O} n, consists of chains formed by Eu atoms ­connected by the carboxyl­ate groups of the benzene-1,4-dicarboxyl­ate (BDC) linker. The chains are inter­connected by BDC linkers, generating a three-dimensional framework with large voids. The Eu atoms are coordinated by seven carboxyl­ate O atoms and one solvent O atom in a sterically constrained manner due to the carboxyl­ate group rigidity, and this causes the coordination to be distorted dodeca­hedral. The ethyl groups of the solvent ligand are disordered in the void. The elongated Eu—O bond to the solvent indicates that it is loosely bound to the framework, and hence solvent exchange may be possible. In the void there is additionally one partly occupied disordered water mol­ecule. [ABSTRACT FROM AUTHOR]

The crystal structure of the title compound, [Gd(C14H8O4)1.5(C5H11NO)] n, comprises chains of Gd atoms intra­connected by the carboxyl­ate groups of the biphenyl-4,4′-dicarboxyl­ate (BPDC) linkers, one of which is disposed about a twofold axis. The Gd atom chains are aligned along the b axis and are inter­connected by BPDC linkers, creating a three-dimensional framework. A single diethyl­formamide (DEF) mol­ecule is bonded to each Gd atom. This mol­ecule is positioned in the cavities formed by the inter­connection of the Gd atom chains via the BPDC linkers. Due to the steric constraints of the carboxyl­ate groups, the square antiprismatic coordination geometry of eight O atoms (one from the DEF mol­ecule and seven from carboxyl­ate groups) around Gd is distorted. [ABSTRACT FROM AUTHOR]

We present a combined experimental and theoretical charge density study of the coordination polymer Zn(HCOO)2(H2O)2, which serves as a nonmagnetic reference for the isostructural magnetic compounds containing 3d transition metals. The charge density has been modeled using the multipole formalism against a high-resolution single-crystal X-ray diffraction data set collected at 100 K. The theoretical model is based on periodic density functional theory calculations in the experimental geometry. To gauge the degree of systematic bias from the multipole model, the structure factors of the theoretical model were also projected into a multipole model and the two theoretical models are compared with the experimental results. All models, both experiment and theory, show that the Zn atom densities are highly spherical but show small accumulations of charge toward the negative ligands. The metal--ligand interactions are found to be primarily ionic, but there are subde topological indications of covalent contributions to the bonds. The source function calculated at the bond critical points reveals a rather delocalized picture of the density in the bridging carboxylates, and this presumably reflects the exchange pathway in the magnetic analogues. [ABSTRACT FROM AUTHOR]

The crystal structure of the title compound, {[Gd2(C8H4O4)3(C5H11NO)2]·H2O} n, consists of chains of Gd atoms inter­connected by a benzene-1,4-dicarboxyl­ate (BDC) linker. The chains are also intra­connected by carboxyl­ate groups from the BDC linker, thus generating a three-dimensional framework with large cavities. The coordination of the eight carboxyl­ate O atoms around the GdIII ion is distorted dodeca­hedral, due to the steric constraints of the carboxyl­ate groups. The large anisotropic displacement parameters of the atoms of the coordinated diethyl­formamide (DEF) and the disorder in their positions indicate loose bonding to the framework, and hence solvent exchange may be possible. Additionally, one water mol­ecule is located in the cavity. [ABSTRACT FROM AUTHOR]

X-ray/neutron (X/N) diffraction data measured at very low temperature (15 K) in conjunction with ab initio theoretical calculations were used to model the crystal charge density (CD) of the host-guest complex of hydroquinone (HQ) and acetonitrile. Due to pseudosymmetry, information about the ordering of the acetonitrile molecules within the HQ cavities is present only in almost extinct, very weak diffraction data, which cannot be measured with sufficient accuracy even by using the brightest X-ray and neutron sources available, and the CD model of the guest molecule was ultimately based on theoretical calculations. On the other hand, the CD of the HQ host structure is well determined by the experimental data. The neutron diffraction data provide hydrogen anisotropic thermal parameters and positions, which are important to obtain a reliable CD for this light-atom-only crystal. Atomic displacement parameters obtained independently from the X-ray and neutron diffraction data show excellent agreement with a |ΔU| value of 0.00058 Å(2) indicating outstanding data quality. The CD and especially the derived electrostatic properties clearly reveal increased polarization of the HQ molecules in the host-guest complex compared with the HQ molecules in the empty HQ apohost crystal structure. It was found that the origin of the increased polarization is inclusion of the acetonitrile molecule, whereas the change in geometry of the HQ host structure following inclusion of the guest has very little effect on the electrostatic potential. The fact that guest inclusion has a profound effect on the electrostatic potential suggests that nonpolarizable force fields may be unsuitable for molecular dynamics simulations of host-guest interaction (e.g., in protein-drug complexes), at least for polar molecules., (© 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)

We present a combined experimental and theoretical charge density study of the coordination polymer Zn(HCOO)(2)(H(2)O)(2), which serves as a nonmagnetic reference for the isostructural magnetic compounds containing 3d transition metals. The charge density has been modeled using the multipole formalism against a high-resolution single-crystal X-ray diffraction data set collected at 100 K. The theoretical model is based on periodic density functional theory calculations in the experimental geometry. To gauge the degree of systematic bias from the multipole model, the structure factors of the theoretical model were also projected into a multipole model and the two theoretical models are compared with the experimental results. All models, both experiment and theory, show that the Zn atom densities are highly spherical but show small accumulations of charge toward the negative ligands. The metal-ligand interactions are found to be primarily ionic, but there are subtle topological indications of covalent contributions to the bonds. The source function calculated at the bond critical points reveals a rather delocalized picture of the density in the bridging carboxylates, and this presumably reflects the exchange pathway in the magnetic analogues.

The Mn atom in the cubic polymorph of CeMnNi(4) appears to be located in an oversized cage-like structure, and anomalously large atomic displacement parameters (ADPs) for the Mn atom indicate that it is a potential "rattler" atom. Here, multitemperature synchrotron powder X-ray diffraction data measured between 110 and 900 K are used to estimate ADPs for the Mn "guest" atom and the "host" structure atoms in cubic CeMnNi(4). The ADPs are subsequently fitted with Debye and Einstein models, giving Θ(D) = 301(2) K for the "host" structure and Θ(E) = 165(2) K for the Mn atom. This is higher than typical Einstein temperatures for rattlers in thermoelectric skutterudites and clathrates (Θ(E) = 50-80 K), indicating that the Mn atom in cubic CeMnNi(4) is more strongly bonded. In order to probe the chemical interactions of the potential Mn rattler atom, atomic Hirshfeld surface (AHS) analysis is carried out and compared with AHS analysis of well-established guest atom rattlers in archetypical skutterudites, MCoSb(3). Surprisingly, the skutterudite rattlers have more deformed AHSs than the Mn atom in cubic CeMnNi(4). This is related to the highly ionic nature of the skutterudite rattlers, which is not taken into account in the neutral spherical atom approach of the AHS. Additionally, visualization of void spaces in the two materials using the procrystal electron density shows that while the Mn atom is tightly fitting in the CeMnNi(4) structure then the La atom in the skutterudite is truly situated in an oversized cage of the host structure. Overall, we conclude that the Mn atom in cubic CeMnNi(4) cannot be coined a rattler.