Coherent X‐Ray Scattering for the Hydrogen Atom in the Hydrogen Molecule
01 May 1965-Journal of Chemical Physics (American Institute of PhysicsAIP)-Vol. 42, Iss: 9, pp 3175-3187
TL;DR: In this paper, the x-ray form factors for a bonded hydrogen in the hydrogen molecule have been calculated for a spherical approximation to the bonded atom, and the corresponding complex scattering factors have also been calculated.
Abstract: The x‐ray form factors for a bonded hydrogen in the hydrogen molecule have been calculated for a spherical approximation to the bonded atom. These factors may be better suited for the least‐squares refinement of x‐ray diffraction data from organic molecular crystals than those for the isolated hydrogen atom. It has been shown that within the spherical approximation for the bonded hydrogens in H2, a least‐squares refinement of the atomic positions will result in a bond length (Re value) short of neutron diffraction or spectroscopic values. The spherical atoms are optimally positioned 0.07 A off each proton into the bond. A nonspherical density for the bonded hydrogen atom in the hydrogen molecule has also been defined and the corresponding complex scattering factors have been calculated. The electronic density for the hydrogen molecule in these calculations was based on a modified form of the Kolos—Roothaan wavefunction for H2. Scattering calculations were made tractable by expansion of a plane wave in spheroidal wavefunctions.
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TL;DR: Tubercidin (7-deazaadenosine, 1a) and several 6-chlorotuber-Cidin derivatives were synthesized including 4-amino-6-chloro-7-β-D-ribofuranosylpyrrolo[2,3-d]pyrimidine-3′,5′-cycyclic phosphate 9 as discussed by the authors.
Abstract: Tubercidin (7-deazaadenosine, 1a) and several 6-chlorotuber-cidin derivatives were synthesized including 4-amino-6-chloro-7-β-D-ribofuranosylpyrrolo[2,3-d]pyrimidine-3′,5′-cycyclic phosphate 9. Isolation of a side product found in the glycosylation step of the reaction sequence proved to be the N-1 ribosyl-attached isomer as shown by X-ray diffraction analysis. All derivatives were tested for in vitro antiviral and antitumor activity.
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TL;DR: In this article, a multipole model of the charge density distribution in the di-substituted alkyne title compound containing weak intramolecular interactions was obtained from high-resolution single crystal diffraction data, which suggests that the cis conformation of the molecule in this particular crystalline state is due to strong intermolecular hydrogen bonding.
Abstract: A multipole model of the charge density distribution in the di-substituted alkyne title compound containing weak intramolecular interactions as defined by the topology of the charge density, has been obtained from high-resolution single crystal diffraction data. Bond paths are located between formally non-bonded C and O atom pairs and also between a pair of O atoms. This observation of weak intramolecular interactions in an experimentally derived charge density proves that the multipole modeling formalism is sufficiently sensitive to detect such features which are small on an absolute scale. Evidence is presented which suggests that the cis conformation of the molecule in this particular crystalline state is due to strong intermolecular hydrogen bonding.
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TL;DR: In this article, the authors measured the Mossbauer spectra, magnetic susceptibilities, cyclic voltammograms, and electronic spectra of the dinuclear iron(II,III) complex, [Fe2(bpmp)(ena)2](BF4)2, and the crystal structure was determined at 293 K, where Hbpmp represents 2,6-bis[bis(2-pyridylmethyl)aminoethyl]-4-methylphenol and Hena is heptanoic acid.
Abstract: The Mossbauer spectra, magnetic susceptibilities, cyclic voltammograms, and electronic spectra of the dinuclear iron(II,III) complex, [Fe2(bpmp)(ena)2](BF4)2, were measured and the crystal structure was determined at 293 K, where Hbpmp represents 2,6-bis[bis(2-pyridylmethyl)aminoethyl]-4-methylphenol and Hena is heptanoic acid. The valence states of the irons of the complex are localized below about 200 K in the Mossbauer time scale (10−7 s), and are delocalized above 260 K. The activation energy of the electron interexchange between Fe2+ and Fe3+ was evaluated to be 15 kJ mol−1 at between 200 and 230 K based on an analysis of the Mossbauer spectra. The complex crystallizes in the monoclinic system, space group P2/c, with a = 10.129(4), b = 23.295(30), c = 11.324(7) A, β = 104.55(4)°, dcalc = 1.34 g cm−3, Z = 2, and molecular formula Fe2F8O5N6C47B2H59. The structure was solved by the heavy-atom method and was refined anisotropically by the least-squares method, employing 1981 unique reflections with |F| >...
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TL;DR: In this article, a new class of deoxyribonucleic acid (DNA)-intercalating antitumor agents, novel 9-anilino-2,3-methylenedioxyacridines (twelve compounds) have been synthesized and evaluated for the activity against L1210 leukemia in vivo.
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TL;DR: In this article, the synthesis and characterization of three copper triphenylacetate-pyridine complexes are reported along with their magnetic and spectral properties: [Cu2(O2CCPh3)4(py)2]·C6H6 (1), [Cu 2(OCPh3]4(π)2 ] (2), and Cu(O 2CCPh 3)2·2py (3).
Abstract: The synthesis and characterization of three copper(II) triphenylacetate-pyridine complexes are reported along with their magnetic and spectral properties: [Cu2(O2CCPh3)4(py)2]·C6H6 (1), [Cu2(O2CCPh3)4(py)2] (2), and Cu(O2CCPh3)2·2py (3). Crystal structure analyses of 1 and 3 have revealed unusual geometries around copper: 1, triclinic, space group P\bar1 with a=19.558(7) b=16.605(6), c=14.997(5) A, α=14.55(2)°, β=97.11(2)°, γ=111.65(2)°, and Z=2; 3, monoclinic, space group P21⁄c with a=8.931(1), b=12.602(1), c=19.578(1) A, β=118.17(0.4)°, and Z=2. The coordination sphere around each copper in the dimeric complex 1 is a highly distorted trigonal bipyramid with bridging triphenylacetato ligands spanning the apical and equatorial positions, resulting in a long Cu–Cu distance of 3.086(1) A. Temperature-dependent magntic susceptibility measurements on 1 indicate that the two coppers are antiferromagnetically coupled with −2J=187 cm−1. The structure of the monomeric complex 3 is unusual in that the out-of-plane...
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TL;DR: In this article, the quantum mechanical wave functions of molecules are discussed and an attempt is made to effect a simultaneous regional and physical partitioning of the molecular density, the molecular pair density, and the molecular energy, in such a way that meaningful concepts can be associated with the density and energy fragments thus formed.
Abstract: The quantum mechanical wave functions of molecules are discussed. An attempt is made to effect a simultaneous regional and physical partitioning of the molecular density, the molecular pair density, and the molecular energy, in such a way that meaningful concepts can be associated with the density and energy fragments thus formed. The origin of chemical binding is interpreted in terms of the concepts formulated in the partitioning process. (T.F.H.)
768 citations
576 citations
TL;DR: The solution of Schroedinger's equation for the normal hydrogen molecule is approximated by the function $C[{e}^{\ensuremath{-}\frac{z({r}_{1}+{p}_{2})}{a}}+{e^{\ensem{-]-{m{e})+{m}−m{n}−n}]$ where m is the distance of one of the electrons to the two nuclei, and r is the distances of one electron to the other electron.
Abstract: The solution of Schroedinger's equation for the normal hydrogen molecule is approximated by the function $C[{e}^{\ensuremath{-}\frac{z({r}_{1}+{p}_{2})}{a}}+{e}^{\ensuremath{-}\frac{z({r}_{2}+{p}_{1})}{a}}]$ where $a=\frac{{h}^{2}}{4{\ensuremath{\pi}}^{2}m{e}^{2}}$, ${r}_{1}$ and ${p}_{1}$ are the distances of one of the electrons to the two nuclei, and ${r}_{2}$ and ${p}_{2}$ those for the other electron. The value of $Z$ is so determined as to give a minimum value to the variational integral which generates Schroedinger's wave equation. This minimum value of the integral gives the approximate energy $E$. For every nuclear separation $D$, there is a $Z$ which gives the best approximation and a corresponding $E$. We thus obtain an approximate energy curve as a function of the separation. The minimum of this curve gives the following data for the configuration corresponding to the normal hydrogen molecule: the heat of dissociation = 3.76 volts, the moment of inertia ${J}_{0}=4.59\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}41}$ gr. ${\mathrm{cm}}^{2}$, the nuclear vibrational frequency ${\ensuremath{
u}}_{0}=4900$ ${\mathrm{cm}}^{\ensuremath{-}1}$.
292 citations
TL;DR: In this paper, a simple wave function for the normal state of the hydrogen molecule, in which both the atomic and ionic configurations are taken into account, was set up and treated by a variational method.
Abstract: A simple wave function for the normal state of the hydrogen molecule, in which both the atomic and ionic configurations are taken into account, was set up and treated by a variational method. The dissociation energy was found to be 4.00 v.e. as compared to the experimental value of 4.68 v.e. and Rosen's value of 4.02 v.e. obtained by use of a function involving complicated integrals. It was found that the atomic function occurs with a coefficient 3.9 times that of the ionic function. A similar function with different screening constants for the atomic and ionic parts was also tried. It was found that the best results are obtained when these screening constants are equal. The addition of Rosen's term to the atomic‐ionic function resulted in a value of 4.10 v.e. for the dissociation energy.
253 citations
133 citations