Low-temperature Crystal Structure Research Articles

Low-temperature structure and hole localization in a one-dimensional chain-ladder composite material Sr 0.4Ca 13.6Cu 24+ yO 41+ z

The low-temperature crystal structure of a composite crystal Sr 0.4Ca 13.6Cu 24+ y O 41+ z was determined by Rietveld analysis of neutron diffraction data using a superspace group approach. Distributions of localized holes was estimated by the bond-valence sum (BVS) calculation based on CuO interatomic distances. The maximum of the BVS wave of ladder-Cu (Cu1) sites was shown to fall with decreasing temperature. It indicates that holes are moved from the ladder to the chain at low temperature.

Low-temperature crystal structures of Tetrakis-μ-3,5-diisopropylsalicylatobis-dimethylformamidodicopper(II) and Tetrakis-μ-3,5-diisopropylsalicylatobis-diethyletheratodicopper(II) and their role in modulating polymorphonuclear leukocyte activity in overcoming seizures

Two binuclear copper(II) complexes of 3,5-diisopropylsalicylic acid were characterized by single crystal X-ray diffraction methods and examined for anti-inflammatory activity using activated polymorphonuclear leukocytes and for anticonvulsant activities using electroshock and metrazol models of seizures. These complexes were crystallized from dimethylformamide (DMF) or diethylether. Tetrakis-μ-3,5-diisopropylsalicylatobis-dimethylformamidodicopper(II) [Cu(II) 2(3,5-DIPS) 4(DMF) 2] I is in space group P 1̄; a=10.393 (2), b=11.258 (2), c=12.734 (2) Å, α=96.64 (2), β=92.95 (2), γ=94.90 (2)°; V=1471.7 (4) Å 3; Z=1. Tetrakis-μ-3,5-diisopropylsalicylatobis-etheratodicopper(II) [Cu(II) 2(3,5-DIPS) 4(ether) 2] II is in space group P 1̄; a=10.409 (3), b=11.901 (4), c=12.687 (6) Å, α=91.12 (5), β=90.84 (5), γ=100.90 (4)°; V=1542 (1) Å 3; Z=1. The structure of I was determined at 140 K from 4361 unique reflections ( I>2 σ( I)) and refined on F 2 to R1=0.04 and wR2=0.09. The structure of II was determined at 180 K from 4605 unique reflections ( I>2 σ( I)) and refined on F 2 to R1=0.05 and wR2=0.13. Each compound is a crystallographically centrosymmetric binuclear complex with Cu atoms bridged by four 3,5-diisopropylsalicylate ligands related by a symmetry center [Cu–Cu i : 2.6139 (9) Å in I and 2.613 (1) in II]. The four nearest O atoms around each Cu atom form a nearly rectangular planar arrangement with the square pyramidal coordination completed by the dimethylformamide (or diethylether) oxygen atom occupying an apical position, at a distance of 2.129 (2) Å in I and 2.230 (3) Å in II. Each Cu atom is displaced towards the DMF (or diethylether) ligand, by 0.189 Å in I and 0.184 Å in II, from the plane of the four O atoms. The crystal structures of I and II are essentially similar to each other, except for the DMF or diethylether accommodation. Many disorder phenomena were found in the crystal structure of I. Copper(II) 2(3,5-DIPS) 4(DMF) 2 inhibited polymorphonuclear leukocyte (PMNL) oxidative metabolism in vitro. This effect was concentration related and significant for concentrations higher than 10 μg or 0.68 nmol/ml. Copper(II) 2(3,5-DIPS) 4(DMF) 2 was more active than the parent ligand, 3,5-DIPS, as has been demonstrated with copper complexes of other non-steroidal anti-inflammatory drugs. The DMF and diethylether ternary complexes of Cu(II) 2(3,5-DIPS) 4 were found to have anticonvulsant activity in the maximal electroshock model of grand mal epilepsy in doses ranging from 26 to 258 μmol/kg of body mass following intraperitoneal, subcutaneous, or oral treatment. The DMF ternary complex was also found to be effective in the subcutaneous injection of metrazol model of petit mal epilepsy. We conclude that both ternary copper complexes are lipophilic and bioavailable, capable of facilitating the inflammatory response to brain injury and causing the subsidence of this response in bringing about remission of these disease states.

Neutral bis(ethylenedithio)tetrathiafulvalene at 100 K

The low-temperature crystal structure of bis­(ethyl­enedi­thio)­tetra­thia­fulvalene (BEDT-TTF), C10H8S8, is similar to its high-temperature structure. The room-temperature central bond lengths of this mol­ecule are often used as reference in empirical methods to estimate the charge carried by the (BEDT-TTF)xn+ cations in the BEDT-TTF mol­ecule-based organic conductors. We show that the method we previously reported can still be used with low-temperature BEDT-TTF salts data. Moreover, we confirm the purely thermal origin of the ordering of the ethyl­ene group.

Neutral bis(ethylenedithio)tetrathiafulvalene at 100 K

The low-temperature crystal structure of bis­(ethyl­enedi­thio)­tetra­thia­fulvalene (BEDT-TTF), C10H8S8, is similar to its high-temperature structure. The room-temperature central bond lengths of this mol­ecule are often used as reference in empirical methods to estimate the charge carried by the (BEDT-TTF)xn+ cations in the BEDT-TTF mol­ecule-based organic conductors. We show that the method we previously reported can still be used with low-temperature BEDT-TTF salts data. Moreover, we confirm the purely thermal origin of the ordering of the ethyl­ene group.

The Modulated Crystal Structure of the Molecular Adduct of 2,4,6-Trinitrobenzoic Acid with 2,6-Diaminopyridine

The 1 : 1 adduct of 2,4,6-trinitrobenzoic acid (tnba) with 2,6-diaminopyridine (2,6-dap), [(2,6-dap)+(tnba)-], has been prepared and the low-temperature crystal structure has been determined by X-ray crystallography. A modulated structure has been identified and refined by using a stacking fault model that requires reflection data to be put on three scales depending on an index condition. Crystals are triclinic, space group P1–, with Z 8 in a cell of dimensions a 13.538(3), b 14.516(4), c 16.480(4) Å; α 97.17(2), β 105.69(2), γ 106.09(2)˚. The structure involves proton transfer from the tnba molecule to the 2,6-dap molecule, with the resulting pyridinium proton and an amine proton interacting with the carboxyl oxygens of the tnba molecule in a primary cyclic hydrogen-bonding association. Additional peripheral hydrogen bonding completes a two-dimensional sheet structure.

B-DNA at atomic resolution reveals extended hydration patterns.

Despite the importance of hydration around DNA in the understanding of its conformation and interactions with other molecules in many biological processes, only limited atomic resolution information is available. Crystal-engineering techniques, which were originally developed to mimic DNA base triplets in a crystal lattice, also eliminate the rotational disorder of oligonucleotides around their helical axis and thereby enhance the resolution of the structure analysis. We have determined the low-temperature crystal structure of the synthetic DNA decamer d(GGCCAATTGG) at atomic resolution (1. 15 A) using 17700 reflections and have characterized the highly organized hydration patterns in both grooves. The narrow d(AATT) minor groove is occupied by an 'extended hydration spine' alternately bridging base pairs and phosphate O1P atoms of opposite strands, while a distinctive pattern of parallel water ribbons is observed in the major groove. This analysis provides structural insight into the correlation found between narrow minor-groove width and occurrence of the B(I) conformation and can be used to design new minor-groove binders. By their location between adjacent helices, two fully hydrated magnesium ions further stabilize the crystal packing. The structure also provides details of the hydration and conformation of G.GC triple helices.

Critical behavior of crystal lattice of NaV 2O 5

Critical behavior of crystal lattice was investigated by X-ray scattering for both stoichiometric NaV 2O 5 and Na-deficient Na x V 2O 5 ( x=0.99–0.96). Critical exponents were determined from superlattice reflections with a wave number vector Q=(1/2,1/2,1/4), specifying a lattice modulation formed below T C=35 K. The previously observed anomalous lattice strain below T C was found to be a secondary order parameter driven by a primary order parameter which is an atomic displacement with Q governing the low-temperature crystal structure. The temperature–concentration phase diagram was also determined and the transition temperature was found to decrease linearly with increasing deficiency x as dT C / dx=4.2 ( K/%).

Low temperature crystal structure of Ni–Mn–Ga alloys

Transmission electron microscope (TEM) observation at room temperature of the low temperature phase of Ni2.14Mn0.86Ga shows stress-induced 5 periodicity modulation along a pseudo-[111] cubic zone axis. On cooling to 173 K, the periodicity changes to 7. In stress-free areas, a [001] zone axis with new lattice parameters for the tetragonal phase was observed. The new lattice parameters are smaller by a factor of √2 than the expected lattice parameters. A new model for the tetragonal compound Ni2MnGa and the non-stoichiometric phases was developed with the help of TEM data, X-ray powder diffraction measurements, and a computational simulation based on the X-ray powder diffraction patterns.

Low temperature superstructure and transfer integrals in κ -(BEDT-TTF) 2Cu[N(CN) 2]X: X = Cl, Br

Low temperature crystal structures and band parameters were presented for the deuterized (d) and the hydrogenized (h) κ-(BEDT-TTF) 2Cu[N(CN) 2]Cl and for deuterized κ-(BEDT-TTF) 2Cu[N(CN) 2]Br. An enhanced molecular dimerization was observed for the Cl salts. Theoretical prediction by H. Kino and H. Fukuyama that the molecular dimerization stabilizes the Mott insulating state was confirmed. Below 200 K, X-ray diffuse scattering study revealed formation of two dimensional a×2 c superstructure in the deuterized κ-(BEDT-TTF) 2Cu[N(CN) 2]Br. The structural disorder for the d-Br salt was observed in the superstructure and in the terminal ethylenes.

Influence of the pressure on the low temperature (7K) crystal structure of the superconducting molecular salt (TMTSF) 2ClO 4

The anion ordering which occurs in (TMTSF) 2ClO 4 at 24 K is characterized by the appearance of b */2 superlattice reflections, without any important change in the basic crystal structure. The intensities of these superlattice reflections have been measured at 7 K (ambient pressure). At the same temperature, these reflections do not appear under pressure (5 kbar). Thus, in the latter case, the anions remain disordered.

Methyl group dynamics in paracetamol and acetanilide: probing the static properties of intermolecular hydrogen bonds formed by peptide groups

Measurements of tunnelling and librational excitations for the methyl group in paracetamol and tunnelling excitations for the methyl group in acetanilide are reported. In both cases, results are compared with molecular mechanics calculations, based on the measured low temperature crystal structures, which follow an established recipe. Agreement between calculated and measured methyl group observables is not as good as expected and this is attributed to the presence of comprehensive hydrogen bond networks formed by the peptide groups. Good agreement is obtained with a periodic quantum chemistry calculation which uses density functional methods, these calculations confirming the validity of the one-dimensional rotational model used and the crystal structures. A correction to the Coulomb contribution to the rotational potential in the established recipe using semi-emipircal quantum chemistry methods, which accommodates the modified charge distribution due to the hydrogen bonds, is investigated.

Neutron-diffraction studies of single crystals ofU2T2In (T=Ni,Pd, Pt)

Neutron-diffraction experiments on single crystals of ${\mathrm{U}}_{2}{T}_{2}\mathrm{In} (T=\mathrm{Ni},$ Pd, Pt) verify the noncollinear magnetic structures found with studies of polycrystalline samples, and determine the values of the ordered moments. Compared to the earlier studies, we find the ordered moments on the uranium atoms larger, and no moment associated with the T atoms, in disagreement with one previous study. The $T=\mathrm{Pt}$ sample has a large electronic specific heat and does not order magnetically. We give a detailed description of the low-temperature crystal structure. Polarized-neutron experiments show that the site susceptibilities of the two independent uranium atoms in ${\mathrm{U}}_{2}{\mathrm{Pt}}_{2}\mathrm{In}$ are substantially different and the conduction-electron polarization is unusually large.

Xylan binding subsite mapping in the xylanase from Penicillium simplicissimum using xylooligosaccharides as cryo-protectant.

Following a recent low-temperature crystal structure analysis of the native xylanase from Penicillium simplicissimum [Schmidt et al. (1998) Protein Sci. 7, 2081-2088], where an array of glycerol molecules, diffused into the crystal during soaking in a cryoprotectant, was observed within the active-site cleft, we utilized monomeric xylose as well as a variety of linear (Xn, n = 2 to 5) and branched xylooligomers at high concentrations (typically 20% w/v) as cryoprotectant for low-temperature crystallographic experiments. Binding of the glycosidic moiety (or its hydrolysis products) to the enzyme's active-site cleft was observed after as little as 30 s soaking of a native enzyme crystal. The use of a substrate or substrate analogue as cryoprotectant therefore suggests itself as a simple and widely applicable alternative to the use of crystallographic flow-cells for substrate-saturation experiments. Short-chain xylooligomers, i.e., xylobiose (X2) and xylotriose (X3), were found to bind to the active-site cleft with its reducing end hydrogen-bonded to the catalytic acid-base catalyst Glu132. Xylotetraose (X4) and -pentaose (X5) had apparently been cleaved during the soaking time into a xylotriose plus a monomeric (X4) or dimeric (X5) sugar. While the trimeric hydrolysis product was always found to bind in the same way as xylotriose, the monomer or dimer yielded only weak and diffuse electron density within the xylan-binding cleft, at the opposite side of the active center. This suggests that the two catalytic residues divide the binding cleft into a "substrate recognition area" (from the active site toward the nonreducing end of a bound xylan chain), with strong and specific xylan binding and a "product release area" with considerably weaker and less specific binding. The size of the substrate recognition area (3-4 subsites for sugar rings) explains enzyme kinetic data, according to which short oligomers (X2 and X3) bind to the enzyme without being hydrolyzed.

The range in static stereochemistry of the cation distortion isomers of the [Cu (chelate)2Cl]+ cation, where chelate=bipy, phen or bipyam. The low temperature crystal structure (150 K) of [Cu (bipy)2Cl] [PF6]·H2O and [Cu (phen)2Cl] [BPh4

Low temperature crystallography (150 K) has been used to confirm that the two extreme [Cu (chelate) 2Cl] [Y] stereochemistries of 3 [Cu (bipy) 2Cl] [PF 6]·H 2O, trigonal bipyramidal and 6 [Cu (phen) 2Cl] [BPh 4], trigonal bipyramidal distorted square based pyramidal, are genuine and static stereochemistries of the copper (II) ion.

分子性伝導体（ＤＭｅ‐ＤＣＮＱＩ）２Ｃｕの物性と低温構造

The mixed-valence Cu salt of DMe-DCNQI provides unique physical properties due to the interaction between the one-dimensional (1D) organic pπ band and the d-orbital of Cu ion. This system is metallic down to very low temperature at ambient pressure in spite of the 1D column structure, whereas the system exhibits a sharp metal-insulator (M-I) transition accompanied by a threefold superstructure under pressure. Reentrant behavior (M-I-M transition) is observed in the boundary pressure region. The selective dueteration of (DMe-DCNQI) 2Cu has enabled to control the chemical pressure. Application of this technique produces the Petf-T phase diagram of this system under ambient pressure. The effect of (chemical) pressure on these transitions in the system is generally understood from the change in charge transfer amount from metal ions to DCNQI molecules by low temperature crystal structure analysis and a doping method.

遷移金属錯体伝導体の開発研究と結晶構造

During the past three decades, the old image of molecular conductors has been changed completely. Nowadays, molecular metals are regarded as clean systems with well-defined Fermi surfaces. X-ray diffraction studies have made a great contribution to this progress. Here a brief survey of our structural studies and development of new molecular metals and superconductors is presented. The main topics are, (1) Peierls distorted structure of partially oxidized platinum complex, (2) discovery of metallic complexes without one-dimensional platinum chains, (3) designing analysis of the first molecular superconductor, (4) discovery of pure π-acceptor superconductors, (5) band structure and low temperature crystal structure analysis and (6) novel highly conducting transition metal complex with extended π-conjugated ligands.

Synthesis and co-ordination chemistry of perfluorovinyl phosphine derivatives. Single crystal structures of PPh(CFCF2)2, cis-[PtCl2{PPh2(CFCF2)}2] and [{AuCl[PPh2(CFCF2)]}2

Reaction of perfluorovinyllithium, derived from CF3CH2F, with chloro-substituted phosphines generated perfluorovinylphosphines of the type PPhm(CFCF2)n and P(CFCF2)nClm (n + m = 3) in high yields. A low-temperature crystal structure determination of the air- and moisture-stable compound PPh(CF=CF2)2 provided the first reported structural data for any perfluorovinyl-containing material. There is considerable variation in the C–F bond distances [1.310(4), 1.321(4), 1.353(3) A] within the perfluorovinyl group in the phosphine. The co-ordination chemistry of these ligands has been investigated via the synthesis of examples of late transition-metal complexes. The results of single crystal structural determinations of cis-[PtCl2{PPh2(CFCF2)}2] and [{AuCl[PPh2(CFCF2)]}2]·0.5CH2Cl2 are reported. In both of these molecules short metal–phosphorus distances [d(Pt–P)av = 2.231(3) and d(Au–P)av = 2.217(2) A] are observed compared with typical distances for similar phosphine complexes. A comparison of the electronic properties of these ligands with those of other phosphines, halogenophosphines and phosphites was made on the basis of a spectroscopic investigation of the carbonyl stretching frequencies of the complexes [Mo(CO)5{PPhm(CFCF2)n}] (n + m = 3).

Die Kristallstruktur von N,N'-Ditosyl-/7-phenylendiamin, Dichtefunktionaltheorie-Berechnungen von Konformationen und Wasserstoffbrücken-Motive von Sulfonamiden / Interactions in M olecular Crystals, 146 [1, 2], The Crystal Structure of N,N'-Ditosyl-p-phenylenediam ine, Density Functional Theory Calculations of Conformations and Hydrogen Bond Motifs in Sulfonamides

In a study preceeding the investigation of a novel class of inclusion compounds, the lowtemperature crystal structure o f the host-m olecule N ,N ’-ditosyl-p-phenylenediamine has been determined. It crystallizes in the monoclinic space group P21/N with two formula units in the unit cell, forming layers of hydrogen-bonded molecules. The essential subunits are rigid phenyl rings and flexible sulfonamide linkages C -N(H)-S(O2)-C, the conformations o f which are discussed by comparison with data from the Cambridge Structural Database and based on density functional theory (DFT) as well as semiempirical PM3 calculations for the selected model compounds, N-methyl-methane-, N-methyl-benzene- and N-phenyl-methane-sulfonamide. The torsion angle dependent energy and enthalpy profiles allow estimates o f the rotational barriers around the C -S-N -C bonds. In addition, potential hydrogen bonding by the host molecule is discussed in comparison to analogous carbonic acid derivatives.

Hydrothermal synthesis and low temperature crystal structure of an ammonium beryllophosphate with the merlinoite topology

Abstract An ammonium beryllophosphate (BeP-MER1) with the merlinoite framework topology has been made by the hydrothermal synthesis. Similar to the mineral merlinoite, BeP-MER1 belongs to the orthorhombic space group, but its unit cell is metrically tetragonal. The framework of a merlinoite structure such as BeP-MER1 can be viewed as the body-centered tetragonal packing of double 8-rings or the stacking of 4.8.8 nets along the c-axis. BeP-MER1 has three-dimensional, intersecting 8-ring channels along the crystallographic [001], [110] and [110] directions. The sites of extra-framework species are located, but the distribution of H2O and NH+4 among these sites are not unambiguously determined. A summary of beryllophosphate zeolite structures provides an interesting comparison among hydrous and anhydrous alkali metal templated beryllophosphate phases.

Unexpectedly Lengthened N-H.Co Hydrogen Bonds?

Low-temperature crystal structures of QuinH(+)Co(CO)(4)(-), 1 (QuinH(+) = quinuclidinium), (DABCO)H(+)Co(CO)(3)P(p-tolyl)(3)(-), 2, and (DABCO)H(+)Co(CO)(3)PPh(2)(p-tolyl)(-), 3 (DABCO = 1,4-diazabicyclooctane), 2 and 3 as their acetonitrile solvates, demonstrate that these salts exhibit intermolecular N-H.Co hydrogen bonding between the cation and anion components. NMR and IR data demonstrate the persistence of these interactions in toluene solution. Such solution-state data, which examine solvated ion pairs, suggest little difference between these salts and the corresponding previously reported salts (DABCO)H(+)Co(CO)(3)L(-) (4, L = CO; 5, L = PPh(3)). However, in the solid state, the N-H.Co hydrogen bonds in 1-3 are some 0.1-0.15 Å longer than would be predicted from consideration of the structures of 4 and 5 and the aforementioned similarity to 4 and 5 in solution. In previous reports we have shown that major steric or electronic changes to the anion or cation have resulted in substantial changes (0.15-0.3 Å) in the N.Co [H.Co] separation for N-H.Co hydrogen bonds in related R(3)NH(+)Co(CO)(3)L(-) (L = CO, PR(3)) salts. In this report, we present examples in which small changes are made to the anion or cation remote from the N-H.Co hydrogen bond. In the solid state, the effect of these small changes on this hydrogen bond is subsumed by the effect of changes in the supramolecular structure. This clearly indicates the sensitivity of the geometry of these hydrogen bonds to the overall balance of intermolecular interactions in the solid state and as such is pertinent to current interest in weak (intermolecular) interactions for which characterization by X-ray crystallography is important.