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The structures of tricarbonyl(formylcyclopentadienyl)manganese(I), [Mn(C6H5O)(CO)3], (I), and tricarbonyl(formylcyclopentadienyl)rhenium(I), [Re(C6H5O)(CO)3], (II), were determined at 100 K. Compounds (I) and (II) both possess a carbonyl group in a trans position relative to the substituted C atom of the cyclopentadienyl ring, while the other two carbonyl groups are in almost eclipsed positions relative to their attached C atoms. Analysis of the intermolecular contacts reveals that the molecules in both compounds form stacks due to short attractive π(CO)...π(CO) and π(CO)...π interactions, along the crystallographic c axis for (I) and along the [201] direction for (II). Symmetry-related stacks are bound to each other by weak intermolecular C-H...O hydrogen bonds, leading to the formation of the three-dimensional network. [ABSTRACT FROM AUTHOR]

The geometrical preferences of hydrogen bonds with azide anion are studied using topological analysis of experimental and calculated electron density distribution. The comparison of electron localization function (ELF) and QTAIM analysis shows the reasons behind the apparent unidirectionality of azide anion's lone pairs. The similarity between hydrogen and coordinated bonds involving azide species is demonstrated viathe analysis of the CSD. [ABSTRACT FROM AUTHOR]

The article discusses a study on the crystal and molecular structures of the compounds [Mn(C5H4I(CO)3], [Re(C5H4I)(CO)3], [Mn2(C12H8(CO)6] and [Re2(C12H8(CO)6]. Zigzag chains are formed by the molecules in the four metal-organic compounds. Weak intermolecular hydrogen bonds join the said chains. Also cited are the methods used to prepare the compounds.

The novel title furazan-containing macrocycle (systematic name: 6,9,14,17-tetraoxa-2,3,5,7,16,18-hexaazatricyclo[13.3.0.- 04.8]octadeca-4,7,15,18-tetraene), C8H10N6O4, (I), is the first macrocycle where the furazan rings are connected via a hydrazine group. In spite of the strain in the 12-membered macrocycle of (I), the geometry of the furazan fragment is the same in (I) and in its acyclic analogue 1,8-bis(5-aminofurazan-4-yloxy)-3,6-dioxaoctane, C10H16N6O6, (II). In both compounds, the participation of the furazan rings in intermolecular hydrogen bonding equalizes the N-O bonds within the furazan rings, in contrast with rings which do not participate in such interactions. [ABSTRACT FROM AUTHOR]

Detailed analysis of the charge density distribution function in the crystal of L-nitroarginine with two crystallographycally distinct molecules using Richard Bader''s ‘Atoms in Molecules’ theory demonstrated the strengthening of hydrogen bonds owing to cooperativity effects and revealed the role of H-bonding in charge transfer in a structurally frustrated system. [Copyright &y& Elsevier]

Topological analysis of the experimental electron density distribution functions for two polymorphs of paracetamol showed that strong H-bonds are responsible for the higher stability of crystal phase I, weak interactions for the higher density of phase II. This made it possible to finally resolve the contradiction between the relative stabilities and the densities of the two paracetamol polymorphs. [ABSTRACT FROM AUTHOR]

The stereoelectronic interaction in the S–C–NH+ fragment and its manifestation in geometry of cations are considered using X-ray diffraction data and quantum-chemical calculations of 5-(2-hydroxyethyl)-1,3,5-dithiazinan-5-ium chloride and bromide. [Copyright &y& Elsevier]

Abstract: Interaction of copper(II) acetate with benzoic acid (benzene-1,3,5-tricarboxylic acid=H3-btc and 3,5-dinitro-benzoic acid=H-dnb) and pyridine (Py) resulted in two mononuclear square-planar complexes with the compositions [Cu(H2-btc)2(Py)2] (1) and [Cu(dnb)2(Py)2] (2). The recrystallization of 2 from dimethylsulfoxide (DMSO) yielded the square-bipyramidal complex [Cu(dnb)2(DMSO)2(H2O)2] (3). Crystal structures of 1–3 were determined by single crystal X-ray diffraction at 100K. The square-planar Cu(II) geometry with the Cu–O and Cu–N distances of 1.924(2), 1.925(2) and 2.024(3) and 2.025(3)Å in 1, and 1.930(4) and 2.033(5)Å in 2 was found. The extended H-bonding system in 1 built on the robust carboxylic synthons is giving rise to the high-ordered porous layered structure. Insight into metal center environment and stabilizing intramolecular short interactions is obtained through quantum theory of atoms in molecules (QTAIM). As revealed by QTAIM, in octahedral complex 3 Cu-dnb and Cu-DMSO bonds are stronger than Cu–N bonds in 1 and 2. [Copyright &y& Elsevier]

Abstract: The annular tautomeric equilibrium of two 4-cyano-3(5)-aminopyrazoles having hydrogen atom or methyl group in position 5(3) was studied by X-ray crystallography for the solid compounds and by DFT B3LYP/6-31G** and CBS-QB3 calculations for the free molecules. The 3-amino tautomer was found to be the more favorable form for the free molecules and the sole form in the solid state. [Copyright &y& Elsevier]

Electron density analysis in the title compound has revealed that, due to H-bond formation, the total charges of the dianion and H5O2 + cation are substantially decreased and bond length distribution in the SO3 moiety can be directly related to the total energy of the cation–anion interactions and partial charges. [Copyright &y& Elsevier]