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1.
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B3LYP/6-31G* calculations indicate that sequential annelation of benzene rings to the rim of corannulene gradually flattens the skeleton. Pentabenzocorannulene is predicted to exhibit nearly barrierless flipping motion at room temperature. A mixed quartic-quadratic potential successfully explains the inversion barrier and curvature (given by the pi-orbital axis vector angle) relationship. 相似文献
3.
Guy Guelachvili K. Narahari Rao Richard H. Tipping Brenda P. Winnewisser Manfred Winnewisser 《Mikrochimica acta》1988,95(1-6):339-343
This paper reports the observation of the far infrared absorption spectrum of a single crystal of N2, measured over absorption paths of 4 cm (lengthwise) and 2 cm (across the crystal). The crystal chamber, with quartz windows, was immersed in a flow of cold helium gas. The spectrum from 20 to 120 cm–1 was recorded in the liquid phase, the-phase, and over the full temperature range of the-phase (35.6–2.0 K) with a Fourier transform spectrometer. The spectral resolution, which was not instrument-limited, and the large path allowed the observation of more detailed multiphonon-transition structure in the spectrum of the-phase than has previously been observed. 相似文献
4.
Tryptophan is an essential amino acid, and understanding the conformational preferences of monomer and dimer is a subject of outstanding relevance in biological systems. An exhaustive first principles investigation of tryptophan ( W ) and its ionized counterparts cations (WC) , anions (WA) , and zwitterions (WZ) has been carried out. A comprehensive and systematic study of tryptophan dimer (WD) conformations resulted in about 62 distinct minima on the potential energy surface. The hydrogen bonds and a variety of noncovalent interactions such as OH‐π, NH‐π, CH‐π, CH‐O, and π‐π interactions stabilized different forms of tryptophan and its dimers. Over all in monomeric conformers which have NH‐O, hydrogen bonds showed higher stability than other conformers. A cursory analysis reveal that the most stable dimers stabilized by hydrogen bonding interactions while the less stable dimers showed aromatic side chain interactions. Protein Data Bank analysis of tryptophan dimers reveals that at a larger distance greater than 5 Å, T‐shaped orientations (CH‐π interactions) are more prevalent, while stacked orientations (π‐π interactions) are predominant at a smaller distance. © 2013 Wiley Periodicals, Inc. 相似文献
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Dispersion relations have been obtained on the basis of linear response theory for helicon waves propagating parallel to a magnetic field applied along the axis of a superlattice. Numerical applications have been made to a Kronig-Penney model and the preliminary results clearly indicate nonlocal effects. 相似文献
7.
Understanding noncovalent interactions on the surfaces of carbon nanostructures (CNSs) is of fundamental importance and also has implications in nano‐ and biotechnology. The interactions of aromatic compounds such as benzene, naphthalene, and aromatic amino acids with CNSs of varying diameter, chirality, and curvature were systematically explored by using density functional theory. Planar graphene exhibits stronger binding affinity than curved carbon nanotubes (CNTs), whereas zigzag CNTs appear to show stronger binding affinity than armchair CNTs. For hydrocarbons, there exist two competing modes, namely, π–π stacking interactions and CH ??? π interactions, which bring the aromatic motifs into parallel and perpendicular dispositions with respect to the CNSs, respectively. Our results reveal that π–π stacking interactions override CH ??? π interactions in such cases. However, in the case of aromatic amino acids, π–π interactions can exist simultaneously along with a range of other interactions, including CH ??? π. The polarizability and HOMO energy of the CNSs were found to be the key factors that determine the binding energies. The HOMO–LUMO energy gaps of the CNSs were found to be undisturbed by the noncovalent functionalization of the aromatic molecules. 相似文献
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9.
A. Valentin A. Henry Ph. Cardinet M.F. Le Moal Da-Wun Chen K. Narahari Rao 《Journal of Molecular Spectroscopy》1978,70(1):9-17
The wavenumbers of the vibration rotation band lines of 14N16O are reported for the , and subbands of the 1-0 transition in the infrared. The full set of spectroscopic constants for this band has been determined by direct approach using the analysis of Zare, Schmeltekopf, Harrop, and Albritton. In addition to the band origin ν0 and the B, D, H constants for the lower and upper vibrational levels, the following spin-orbit coupling constants have been derived: and (in cm?1). Apparent centrifugal corrections to these constants have been determined and the values obtained for them are and . Λ-Type doubling constants evaluated by using both grating and tunable laser data are also reported. 相似文献
10.
The previously reported (J. Mol. Spectrosc.68, 195–222 (1977)) study of the CH3D spectrum occurring at 1033–1270 cm?1 which was mainly concerned with the ν6 fundamental has now been extended to cover the region 1270–1420 cm?1. In all, 342 transitions belonging to the ν3 band are now assigned. Both the ν3 and ν6 bands are processed simultaneously taking into account of the Coriolis interaction between them, and the fitting of all the experimental data led to 21 significant spectroscopic constants for the states v6= 1 and v3 = 1 of CH3D. 相似文献