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Ab initio molecular orbital and density functional theory (DFT) in conjunction with different basis sets calculations were performed to study the N&bond;H...O and S&bond;H...O blue-shifted H-bonds in the HNO...HFSO2 complex. The geometric structures, vibrational frequencies, and interaction energies were calculated by both standard and CP-corrected methods. Natural bond orbital (NBO) analysis was used to investigate the origin of blue-shifted H-bonds, showing that the decrease in the σ*(N&bond;H) and σ*(S&bond;H) is due to the electron density redistribution effect. The structure reorganization effect on the blue-shifted hydrogen bonds was discussed in detail. © 2006 Wiley Periodicals, Inc. Int J Quantum Chem, 2007 [ABSTRACT FROM AUTHOR]

Furan dimer (C4H4O)2 was subjected to density functional theory (DFT). Four equilibrium isomers were located, and the most stable isomer has two strong O⋯H–C hydrogen bonds which interactions are enhanced by the presence of the cooperation effect. The interaction energies were calculated and the effects of basis set superposition errors (BSSE) were systematically considered. The natural bond orbital (NBO) analysis was performed to understand better the nature of the corresponding intermolecular interactions. All the results indicate that I and II are formed via hydrogen-bonding interactions, and van der Waals interactions play a key role in the formation of III and IV. [Copyright &y& Elsevier]

Abstract: The hydrogen bonding interaction of formamide–nitrosyl hydride complex has been investigated using density functional theory (DFT) and ab initio method. The natural bond orbital (NBO) analysis and atom in molecules (AIM) theory were applied to understand the nature of the interaction. Two stable geometries are found on the potential energy surface, a six-membered cyclic structure of complex A and a seven-membered cyclic structure of complex B, characterized by AIM analysis. Complex A is less stable than complex B. It is confirmed that there are contractions of Ced with the monomer HCONH2), Ncompared with the monomer HNO) and the corresponding stretching vibrational frequencies are blue-shifted, while there is an elongation of the Nd the corresponding stretching vibrational frequency is red-shifted, relative to those of the monomer HCONH2. From NBO analysis, it is evident that the electron densities in the σ ∗ (Ce:italic>σ ∗(N complex A are less than those of the monomers HCONH2 and HNO, which strengthen Ce:glyph name="sbnd" />H bonds. Furthermore, the increases in s-characters of X also strengthen X/ce:simple-para> [Copyright &y& Elsevier]

Acetic acid (CH3COOH) and pyridine (C5H5N) 1:1 complex was subjected to Density Functional Theory (DFT) calculations using 6-311G(d,p) basis set. Five equilibrium isomers were located, and the most stable structure has a strong N⋯H–O hydrogen-bonding interaction. A normal-mode analysis of the vibrations of the five isomers was carried out and compared with the experimental values. The calculations indicate that solvents enhance significantly the strength of hydrogen bond as shown by the decrease of the N–H distance and appreciable red shift of the H–O vibration mode and blue shift of N⋯H–O vibration mode. [Copyright &y& Elsevier]

Abstract: The adsorption behavior of iron phthalocyanine (FePc) on the Cu(100) surface at the initial stage has been investigated by combining scanning tunneling microscopy (STM) and density functional theory (DFT) calculations. At low coverage, FePc molecules deposited on the sample surface at room temperature tend to adsorb dispersedly with their molecular planes parallel to the crystallographic directions of the substrate. Another interesting STM observation for the sub-monolayer coverage is that the molecular axes of FePc are aligned along [037] (as well as ) azimuth. At the monolayer coverage and elevated temperature, two types of ordered structures are observed. The FePc adsorption sites for the experimentally observed two distinct ordered domains have been revealed through DFT calculations. With further increasing the coverage, molecular clusters are formed particularly near the step edges. [Copyright &y& Elsevier]

Abstract: The adsorption of perylene on Si (001) surface has been studied by UPS measurement and DFT calculation. With 0.5 monolayer, the perylene molecule adsorbs uprightly with its long axis cross the dimer. At the coverage of 1.0 monolayer, the perylene molecule adsorbs uprightly with its short axis cross the dimer. To increase the separation between the molecules, the molecules adsorb forming a zigzag structure. With coverage increasing, the work function decreases. When the coverage is 1ML, the work function is the minimum. The dipole, formed on the surface, contributes to the change in work function. [Copyright &y& Elsevier]

Abstract: The ordered adsorption structures of FePc on Cu (100) have been studied by scanning tunneling microscopy (STM) and density functional theory (DFT) calculations. With the deposition rate beyond 0.5 ML per min, the FePc molecules are not deposited dispersedly but are deposited as molecular clusters. After the heat treatment (the temperature higher than 420K), the ordered organic structures of p(5×2) or p(2×5) are obtained. The ordered adsorption structures are in the tilt adsorption model. The FePc molecules in the different domains are aligned along the [011] or [] azimuth, respectively, the molecules are tilted. [Copyright &y& Elsevier]

Abstract: Using a combination of scanning tunneling microscopy (STM) and density functional theory calculations, we have studied the adsorption of tetracene on the Cu(110) (2×1)O substrate. At monolayer coverage the adsorbed molecules are in the flat-laying geometry with their long axis along the close-packed [001] direction of the substrate and a long-range ordered structure on the length scale up to 100nm has been observed. DFT calculation results indicate a stronger interaction between tetracene molecules and Cu(110) substrate than Cu(110) (2×1)O substrate. The preferential adsorption sites have also been pointed out on both substrates. The observed wavelike structure is explained by the interdigitation of C–H bonds of adjacent molecules. [Copyright &y& Elsevier]

Abstract: The growth of tetracene on SiO2/Si(111) substrate has been studied by ultraviolet photoemission spectroscopy measurements. Seven emission features of the organic material are located at 2.26, 3.56, 4.77, 5.88, 6.98, 8.18 and 9.90eV, respectively, below the Fermi level. The changes in binding energy and work function during the deposition of tetracene molecules on SiO2 substrate indicate an interaction between tetracene molecule and substrate. The interaction between tetracene molecule and substrate is weaker than that between the organic and silicon substrate. The reduction in work function is due to the formation of interface dipole. Based on the density functional theory (DFT) calculation, tetracene molecules are arranged in an upright standing manner with the optimal growth of a small cluster consisting four molecules. [Copyright &y& Elsevier]

Abstract: The monolayer structures of perylene adsorbed on Ag(110) surface were studied by combining scanning tunneling microscopy (STM) experiments and density functional theory (DFT) calculations. Several superstructures (i.e. loose and compact dimer structures, compact trimer structures) were observed. DFT calculation results show that the interaction between molecule and Ag substrate is weak, the intermolecular interaction is comparable with that between molecule and substrate. The organic self-assembly on metal surface results from the balance between intermolecular interaction and molecule–substrate interaction. On Ag(110) surface, the dimer-α structure was found to be more stable than other structures. [Copyright &y& Elsevier]

Abstract: Resonance Raman spectra were acquired for acetophenone using 228.7, 239.5, and 245.9nm excitations in cyclohexane solution. The spectra display overtones of the benzene ring C–C stretch (1578cm−1) and the carbonyl C (1671cm−1) modes and their combination bands with other five vibrational modes. A preliminary resonance Raman intensity analysis was done and these results for acetophenone were compared to the those previously reported for 2-hydroxyacetophenone. The differences between the vibrational reorganizational energies for acetophenone relative to those of 2-hydroxyacetophenone were briefly discussed. [Copyright &y& Elsevier]

Abstract: Resonance Raman spectra of p-nitroacetophenone(PNAP) have been obtained in resonance with the charge-transfer (CT) band using 252.7, 266 and 273.9nm in methanol solvent. The spectra indicate that the Franck–Condon region photodissociation dynamics have multidimensional character with motion mainly along the Cing ν 8(1691cm−1) and the benzene ring stretch ν 10(1593cm−1). A preliminary resonance Raman intensity analysis was done and the results for PNAP were compared with nitrobenzene and aceptophenone. Our results indicate that –NO2 is more photoactive than –COCH3. The isomerization process of PNAP takes place somewhere after the wave packet leaves the Franck–Condon region. [Copyright &y& Elsevier]