The electron density distribution in CN−, LiCN and LiNC. The use of minimal and extended basis set SCF calculations

Electron density maps are reported for the CN−ion and the LiCN and LiNC molecules, calculated from molecular wave-functions near the Hartree-Fock limit. The electron density distribution derived from CNDO/ 2 wavefunctions does not resemble the ab initio results. The ultimate ability of a minimal basis set to represent the electron density near the Hartree-Fock limit, has been tested. The requirement of N-representability of the trial electron density has been satisfied. It is found that the molecular valence density cannot be reproduced to a satisfactory extent by a minimal set of Slater orbitals, even when the exponents of the basis orbitals are optimized

An electron density study of sodium sulfanilate dihydrate at 78 K

The crystal structure of sodium sulfanilate dihydrate has been redetermined from single-crystal X-ray data collected at 78 K. Separate least-squares refinements were performed on the low-order data, the high-order data and the entire data set. The nonplanarity of the amino group has been reconfirmed. Difference density maps, based on the atomic parameters from the high-order refinement, are interpreted in terms of bonding effects. An analysis of the charge distribution led to net charges of -0.37 (4), +0-07 (4) and +0.15 (4) e for the sulfanilate group, Na atom and hydrate molecules respectively

The crystal structure of urea oxalic acid (2:1)

The crystal structure of urea oxalic acid, 2[CO(NH2)2].(COOH)2 has been determined using three-dimensional X-ray data, collected on an automatic diffractometer. The space group is P21/c. The lattice constants are: a = 5.058 (3), b = 12.400 (3), c = 6.964 (2) A, fl= 98"13 (7) °. The number of molecules in the unit cell is two. The structure consists of layers of urea and oxalic acid molecules held together by hydrogen bonds. The positions of all hydrogen atoms have been found. The compound is not a uronium salt

A comparison of the theoretical and experimental electron density distribution in the cyanide and thiocyanate group

Electron density distributions, derived from ab initio molecular wavefunctions, have been calculated for CN− and SCN− ions. From these dynamic densities were calculated assuming rigid body thermal vibrations of the molecules. Comparison with the difference density in NaCN - 2H2O, NaSCN and NH4SCN, observed by X-ray diffraction, is fair. Remaining differences between theory and experiment are discussed. The Hartree-Fock method gives a better correspondence with the observed electron density distribution in the thiocyanate ion than the Hartree-Fock-Slater method

One-dimensional zinc(II) fumarate coordination polymers

<div><p>A new procedure developed for the synthesis and crystallization of various zinc(II) fumarate hydrate coordination polymers is described. In the first step, anhydrous Zn(II) fumarate, [Zn(C₄H₂O₄)] (<b>1</b>), is synthesized from Zn(II) acetate and fumaric acid in methanol. Subsequently, this product is used as a starting material for growing small crystals of bis–aqua Zn(II) fumarate, [Zn(H₂O)₂(C₄H₂O₄)] (<b>2</b>), triaqua Zn(II) fumarate monohydrate, [Zn(H₂O)₃(C₄H₂O₄)]·H₂O (<b>3</b>), tetraaqua Zn(II) fumarate, [Zn(H₂O)₄(C₄H₂O₄)] (<b>4</b>), and tetraaqua Zn(II) fumarate monohydrate, [Zn(H₂O)₄(C₄H₂O₄)]·H₂O (<b>5</b>). All structures were determined or redetermined by X-ray structure analyses. The hitherto unknown compound <b>3</b> exhibits a zig-zag chain structure with five-coordinate Zn(II) ions.</p></div

Neutronenstreuung zur Kristallchemie und zum Realbau von Kristallen

TIB: D.Dt.F./AC 1000 (17,73) / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekSIGLEDEGerman