Crystal packing molecular structures

In 1990, Baumeister et al. [127] described the crystal and molecular structure of 4-ethoxy-3 -(4-ethoxyphenyliminomethyl)-4 -(4-methoxy-benzoy-loxy)azobenzene. The molecules have a bifurcated shape. The phenyliminom-ethyl branch is bent markedly from the nearly linear three ring fragment, but is almost coplanar with the azobenzene moiety. They found that the molecular conformation is affected by an intramolecular interaction of the carboxylic and azomethine groups. The crystal packing was described in terms of a sheet structure with interdigitating rows of molecules. 

Oi T, Odagiri T, Nomura M (1997) Extraction of lithium from GSJ rock reference samples and determination of their lithium isotopic compositions. Anal Chim Acta 340 221-225 Oi T, Shimizu K, Tayama S, Matsuno Y, Hosoe M (1999) Cubic antimonic acid as column-packing material for chromatographic lithium isotope separation. Sep Sci Tech 34 805-816 Olsher U, Izatt RM, Bradshaw JS, Dailey NK (1991) Coordination chemistry of lithium ion a crystal and molecular structure review. Chem Rev 91 137-164... 

The crystal and molecular structure data of the three Se8 forms listed in Table II have been determined by X-ray diffraction (27-29, 31). a-, /3-, and y-cyclooctaselenium crystallize in the same space group but differ in the packing of the molecules (see Fig. 4). The average bond distances, bond angles, and torsional angles of the Se8 molecules are identical within the limits of the standard deviation. The torsional angle of 101° is close to the value of 99° observed in the case of Sg (36) and obviously corresponds to the minimum of the torsional potential energy function. The shortest intermolecular distance has been observed in the case of -y-Se8 the value of 334.6 pm is even smaller than the shortest intermolecular contact in orthorhombic cy-clooctasulfur, S8 [337 pm (33)]. 

The crystal and molecular structure of eight different complexes was established by X-ray analysis, indicating three types of disulfide arrangements in the crystal lattice. All crystals are built up from DGTD molecules packed along the twofold symmetry axes and solvent molecules located around the twofold... 

Berkovitch-Yellin, Z. and Leiserowitz, L. (1984) The role played by C-H- - -O and C-H- - -N interactions in determining molecular packing and conformation, Acta Cryst. B40, 159-165. Parthasarathy, R., Fridey, S.M., and Srikrishnan, T. (1989) Conformation and hydrogen bonding of A-formylmethionyl peptides. II. Crystal and molecular structure of iV-formyl-L-methionyl-L-phenylalanine, Int. J. Peptide Protein Res. 33, 308-312. 

Crystals of endo-Su (a-Sig) are intense lemon-yellow, rhombic plates and belong to the orthorhombic crystal system. The molecules are arranged to form a pseudohexagonal close packing which accounts for the higher density of the endo-Sis crystal. Crystals of exo-Sig (PSu) are monoclinic. The crystal and molecular structure data are summarized in Table 15. A detailed analysis and modeling of the intermolecular forces in 12 sulfur allotropes... 

Crystal and molecular structures of 3 bile salt hydrates have been solved [7,51,53]. The crystallographic data (Table 2) show that all are monoclinic with 2 molecules in each unit cell. Whereas the anions are held together mainly by ion-ion and ion-dipole interactions between the counterions and the carboxylate and hydroxyl groups to which water molecules contribute, the crystal packing patterns are remarkably similar (Figs. 4 and 5). The crystal packing upon looking down the b... 

W. Mackie, B. Sheldrick, D. Akrigg, and S. Perez, Int. J. Biol. Macromol. 8, 43 (1986). Crystal and Molecular Structure of Mannotriose and Its lationship to the Conformations and Packing of Mannan and Glucomannan Chains and Mannobiose. 

The crystal and molecular structure of a tri-O-ethylamylose polymorph, TEA-3, has been solved by stereochemical conformation and packing analysis, combined with X-ray fibre diffraction analysis. The unit cell is orthorhombic, space group jP2i2i2i, with a = 15.36 ( 0.03)A, Z> = 12.18 ( 0.05)A, and c (fibre repeat) = 15.48 ( 0.01) A. The actual chain conformation is a 43 helix with the 6-ethoxy-group in the tg position, as was previously found for the polymorph TEA-1. 

Figure 3.4 Molecular (a and b) and crystal packing (c) structures of methano-indene-fullerene, C6o(CH2)(Ind). A black circle denotes the dihydro-methano group (ref. 78) 2013 WILEY-VCH Verlag GmbH Co. KGaA, Weinheim.

Other compounds characterized and analyzed by XRD, with other complementary techniques used, include the sterically-crowded triarylphos-phines with formyl and benzoyl groups, benzyl(triphenyl)phosphonium dichloroiodate, the A,A-bis(terphenyl)aminophosphenium cation, dithiophosphinate ligands, and mercury(II) complexes of a-keto stabilized phosphorus ylides. Also, the crystal and molecular structure of 2-(4-chlorophenyl)-5,7-dimethoxyquinolin-4-yl phenyl bis(2-chloroethyl)phos-phoramidate (32) has been determined by NMR, IR, and XRD analysis. The crystal is triclinic, PI space group, a = 9.5188 A, )= 12.856 A, c= 13.250 A, F= 1412.0 A, and Z = 2 (at 291K). The crystal packing... 

The parameters in the original parameterization are adjusted in order to reproduce the correct results. These results are generally molecular geometries and energy differences. They may be obtained from various types of experimental results or ah initio calculations. The sources of these correct results can also be a source of error. Ah initio results are only correct to some degree of accuracy. Likewise, crystal structures are influenced by crystal-packing forces. 

Whenever the polymer crystal assumes a loosely packed hexagonal structure at high pressure, the ECC structure is found to be realized. Hikosaka [165] then proposed the sliding diffusion of a polymer chain as dominant transport process. Molecular dynamics simulations will be helpful for the understanding of this shding diffusion. Folding phenomena of chains are also studied intensively by Monte Carlo methods and generalizations [166,167]. 

---