Theoretical study of energies,structures, and vibrational spectra of the carbonic acid–hydroperoxy radical complexes

In this work, we present the results for the first time of our study on hydrogen‐bonded H₂CO₃–HO₂ complexes (structures 1, 2) by means of ab initio molecular orbital theory. These complexes are important intermediates in the reaction of the hydroperoxy radical and cabonic acid. We calculated that these structures are a six‐membered ring. We found that the binding energy of two complexes are 5.8 and 9.3 kcal/mol using the CCSD(T) method. We also calculated the vibrational and rotational frequencies for these complexes. © 2004 Wiley Periodicals, Inc. Int J Quantum Chem, 2005     

Hybrid iodoperfluoroalkane-ferrocene supramolecular arrays: the shortest contacts iodine forms with nitrogen atoms and unsaturated moieties

α,ω-Diiodoperfluoralkanes self-assemble in solution and in the solid phase with (S)-(−)-N,N-dimethyl-1-ferrocenylethylamine. The formed adducts have been characterized by DSC, IR, Raman, and NMR techniques. Single crystal X-ray analysis of one of the obtained adducts shows that perfluorinated and organometallic modules alternate giving rise to infinite one-dimensional (1D) chains. The interacting modules are connected through strong n-type halogen bondings, involving nitrogen and iodine atoms, and weak π-type halogen bondings, involving Cp rings and iodine atoms. Both interactions are the shortest reported to now in their respective classes. Theoretical calculations have been performed to quantify the observed π-type halogen bonding. For the first time a metallocene-perfluorocarbon (PFC) hybrid material is described.     

Vibrational spectra, structure and hydrogen bonding of 5-tert-butylpyrazole and its zinc complexes

New zinc complexes [L₂ZnX₂] with X=Cl (I), Br (II), I (III) and NO₃ (IV), [L₃Zn(OClO₃)]ClO₄ (V) and [L₄Zn](ClO₄)₂ (VI) with 5-tert-butylpyrazole as ligand L were synthesized and characterized by infrared-, Raman-, mass- and NMR-spectroscopy. The assignment of the vibrational frequencies for the complexes in the range of 4000–80 cm⁻¹ is proposed. Analysis of the IR spectra in the range of ν_NH frequencies shows that 5-tert-butylpyrazole forms cyclic associates in the solid using intermolecular NHN hydrogen bonds. This was proven by a crystal structure determination, which showed that L exists as tetramers in the solid state. In solution there is an equilibrium between tetramers and monomers and, probably, dimers or trimers. In the complexes, the NH-groups of L form intramolecular H-bonds with the X-group. The intramolecular H-bond in VI has interionic character and partially dissociates in solution at high dilution. Ligand vibrations that are sensitive to the coordination and the dependence of their frequencies on the anionic group X has been revealed.     

The change in the vibrational anharmonicity for FHRg, FArHRg, FArHN2 and FArHP2 (Rg=Ne, Ar, Kr)

The change in the vibrational anharmonic constant for the linear hydrogen-bonded complexes FHRg, FArHRg, FArHN₂, FArHP₂ (Rg=Ne, Ar, Kr) was determined at the MP2/6-311++G(3df,3pd) level of theory. It was found that in the vibrationally red-shifted complexes, hydrogen bond formation increases the anharmonic constant while in the vibrationally blue-shifted species (except FArHNe) the anharmonic constant decreases on complexation.     

Hydrogen bonding in 2-hydroxybenzoyl and 2-hydroxythiobenzoyl compounds: Spectroscopic characterization and spectroscopic bond strength sequences

Summary A survey of IR and NMR spectroscopic data is given for 30 2-hydroxybenzoyl and 2-hydroxy-thiobenzoyl compounds, which are representative for various kinds of (thio)carbonyl groups. The data shall provide a basis for a comparison between corresponding intramolecular O-H··O and O-H··S hydrogen bonds and for the evaluation of systematic dependencies. Correlations between v_OH frequencies, which are considered as the main characteristic of hydrogen bond strengths, and several other spectroscopic quantities are shown. For O-H··O type associations the bond strength sequence is acid chloridesOH-Frequenzen, die als wesentliches Kriterium zur Charakterisierung der Bindungsstärken herangezogen werden, und verschiedenen anderen spektroskopischen Daten werden gezeigt. Bei den Wasserstoffbrückenbindungen des Typs O-H··O nehmen die Bindungsstärken in der Reihenfolge SäurechlorideCO-Frequenzen. Die auffällige Sonderstellung der tertiären Amide ist auf sterische Effekte zurückzuführen. Die v_OH-Frequenzen der O-H··S Wasserstoffbrückenbindungen sind denen der entsprechenden O-H··O Bindungen sehr ähnlich, ausgenommen Thiosäuren und Thioester, für die wesentlich niedrigere Frequenzen gefunden wurden.     

SCF-CI studies of the equilibrium structure and the proton transfer barrier H3O 2 −

Large-scale configuration interaction (CI) calculations have been performed in order to study the effect of the correlation energy on the equilibrium geometrical structure, the stability, and on the energy barrier of the proton transfer reaction in the hydrogen bonded system HO^– · HOH. An extended Gaussian basis set including polarization functions on each nuclear centre has been employed to approximate the molecular Orbitals. All possible single and double replacements resulting from a single determinant Hartree-Fock reference state have been taken into account in the CI wavefunction. Compared to the SCF results the equilibrium oxygen/oxygen distance has been obtained from the CI calculations to be smaller by about 0.08 Å and the correlation energy has been found to stabilize the composed system by 3.6 kcal/mole. An almost symmetric equilibrium structure with the hydrogen bonding H-atom midway between the two oxygen centres has been obtained in the CI treatment, whereas SCF calculations yield an asymmetric geometrical configuration with a small energy barrier of 1.4 kcal/mole for the proton transfer process.     

Mechanical properties of the Ni filler metal layer in Si3N4 joints measured by nanoindentation

Nanoindentation experiments were done on Si₃N₄/Ni/Si₃N₄ specimens bonded at different temperatures. Tests were carried out in both the ceramic adherent and the metal filler. Results from nanoindentation experiments done across the interlayer verify that a solution of Si atoms in the Ni interlayer did not modify the mechanical properties of the metal (elastic modulus and hardness). The increase in bonding temperature produced an increase in hardness in the metal interlayer but did not affect its elastic modulus. This hardening of the Ni interlayer was related to the decrease in the shear strength of these joints. Copyright © 2004 John Wiley & Sons, Ltd.     

A Sterically Hindered Phosphonic Acid with a Hydrogen‐Bonded Cage Structure: [4‐tert‐Bu‐2,6‐Mes2‐C6H2P(O)(OH)2·H2O]4

The synthesis and molecular structure of the novel phosphonic acid 4‐tert‐Bu‐2,6‐Mes₂‐C₆H₂P(O)(OH)₂ ( 1 ) is reported. Compound 1 crystallizes in form of its monohydrate as a hydrogen‐bonded cluster ( 1·H₂O )₄ comprizing four phosphonic acid molecules (O···O 2.383(3)‐3.006(4) Å). Additionally, sterically hindered terphenyl‐substituted phosphorus compounds of the type 4‐tert‐Bu‐2,6‐Mes₂‐C₆H₂PR(O)(OH) ( 5 , R = H; 7 , R = O₂CC₆H₄‐3‐Cl; 9 , R = OEt) were prepared, which all show dimeric hydrogen‐bonded structures with O···O distances in the range 2.489(2)–2.519(3) Å. Attempts at oxidizing 5 using H₂O₂, KMnO₄, O₃, or Me₃NO in order to give 1 failed. Crystallization of 5 in the presence of Me₃NO gave the novel hydrogen bonded aggregate 4‐tert‐Bu‐2,6‐Mes₂‐C₆H₂PH(O)(OH)·ONMe₃ ( 6 ) showing an O–H···O distance of 2.560(4) Å.     

渣油中沥青质胶粒缔合状况初探

目前一般认为[1] ,石油中的沥青质的基本结构是以多个芳香环组成的稠合芳香环系为核心 ,周围连接有若干的环烷环 ,芳香环和环烷环上都还带有若干个长度不一的正构烷基侧链 ,其中还杂有各种含硫、氮、氧的基团 ,同时还会络合钒、铁等金属。这种以一个稠合的芳香环系为核心的结构是组成胶质或沥青质的基本单元。大量研究表明 ,沥青质由若干个这类单元结构组成 ,以缔合状态存在 ,渣油及其沥青质的分子量都随测定所用溶剂的极性不同而变化 ,在弱极性有机溶剂中所测得的分子量较大 ,在强极性的有机溶剂中所测得的分子量偏小。初步研究表明 ,沥青…     

Inclusion Compounds of Thiourea and Paralkylated Ammonium Salts. Part VII. Hydrogen-Bonded Host Lattices Constructed from Thiourea and Anionic Species Derived from Benzoic Acid

New inclusion complexes (n-C₃H₇)₄N⁺C₆H₅CO ₂ ^– · 3(NH₂)₂CS (1), (n-C₄H₉)₄N⁺[(C₆H₅CO₂)₂H]^–·6(NH₂)₂CS (2) and (C₂H₅)₄N⁺C₆H₅CO ₂ ^– ·(NH₂)₂CS (3) have been prepared and characterized by X-ray crystallography. Crystal data, MoK radiation: 1, space group P2₁2₁2₁, Z = 4, a = 8.544(3), b = 14.588(4), c = 24.448(4) Å, and R1 = 0.062 for 1536 observed data; 2, space group Pbcn, Z = 4, a = 24.938(3), b = 8.911(1), c = 23.733(9) Å, and R1 = 0.055 for 2132 observed data; 3, space group P2₁2₁2₁, Z = 4, a = 9.996(2), b = 10.122(4), c = 18.350(2) Å, and R1 = 0.049 for 1180 observed data. In the crystal structure of 1, the (n-C₃H₇)₄N⁺ cations are stacked in a single column and accommodated within each channel built up by wide thiourea ribbons and benzoate ions via N—H···O hydrogen bonds. In the crystal structure of 2, the tetrabutylammonium cations are arranged in a zigzag column within each channel built of parallel corrugated thiourea layers that are inter-linked by dimeric [(C₆H₅CO₂)₂H]^– groups through N—H·O hydrogen bonds. In compound 3 the (C₂H₅)₄N⁺ cations are accommodated in pseudo-channels generated from infinitely extended thiourea-benzoate composite ribbons.