Structures and stabilities of C2H2F3+ cations: an abinitio molecular orbital study
4
Citation
0
Reference
10
Related Paper
Citation Trend
Abstract:
Eleven stationary points on the singlet C 2 H 2 F 3 + potential energy surface have been calculated using the 3-21G basis set, and characterized as minima (four structures) or first-order saddle points (seven structures) by vibrational analysis. To check the reliability of this basis set, three of the structures have also been optimized at the 6-31G* level; although the geometries change somewhat, the relative energies and nature (maxima, minima) of the structures remain the same. For CF 3 CH 2 + the minimum energy structure has one C—F bond coplanar with the vacant p-atomic orbital at the cationic centre. The structure is 16.4 kcal/mol less stable than the lowest energy conformation of FCH 2 CF 2 + , and the barrier for the 1,2 fluorine migration which connects the two structures is low. The cation F 2 CHCHF + has a conformation that is a minimum on the potential energy surface that is 16.9 kcal/mol higher in energy than FCH 2 CF 2 + ; the two structures are separated by a barrier for 1,2 hydrogen migration of 23.5 kcal/mol. The electronic effects in the various structures have been studied using a quantitative PMO analysis of the interactions between the two carbon fragments of the ions. For CF 3 CH 2 + the net effect of the fluorine is highly destabilizing; the principal stabilizing interactions between CF 3 + and CH 2 consist of π donation from CF 3 + to CH 2 and homoconjugation of a fluorine lone pair with the cationic centre. No net stabilization attributable to fluorine bridging could be found.Keywords:
Lone pair
Fluorine
Potential energy surface
Molecular geometry
Based on the helical and rotational symmetries and Tersoff potential, the structural parameters, i.e., bond lengths and bond angles, have been investigated for armchair single-wall carbon nanotubes. The bond lengths and bond angles are determined for several radii tubes of various lengths. Results for armchair tubes show that one bond length is greater than that of the graphite while the other is smaller. Furthermore, the tube length is found to have significant effects on these bond lengths and bond angles. We have also recalculated the variation of these bonds under hydrostatic pressure. With the application of pressure, the bond lengths compress and the larger bond length decreases faster with pressure in comparison to the shorter one. As a consequence, at some critical pressure the bond lengths become equal. An analysis regarding the cross-sectional shape of the nanotubes and its pressure dependence has also been done. At some particular pressure, the first transition from circular to elliptical cross section takes place. For (10,10) tube the first transition pressure is found to be equal to $2.2\phantom{\rule{0.3em}{0ex}}\mathrm{GPa}$.
Hydrostatic pressure
Molecular geometry
Single bond
Cite
Citations (26)
Molecular geometry
Bent bond
Single bond
Cite
Citations (8)
Molecular geometry
Line (geometry)
Cite
Citations (1)
Molecular geometry
Energy minimization
Bond energy
Butane
Single bond
Parametrization (atmospheric modeling)
Cite
Citations (6)
We have studied bond length and bond angle of a series of phenols. For present study the molecular modelling and geometry optimization of all the compounds were carried out with MOPAC software using MINDO/3 methods. We have conclude that the order of bond lengths between C-O, C-C, C-H and O-H atoms have been changed by changing the position of the substituents i.e., from ortho to para substitution. The C-C-C band angles have the same value while the C-C-O and C-O-H band angles differ from their normal values on substitution.
MINDO
Molecular geometry
Cite
Citations (2)
Zigzag
Molecular geometry
Single bond
Bond energy
Cite
Citations (19)
Bond-length distributions have been examined for 33 configurations of the metalloid ions and 56 configurations of the post-transition metal ions bonded to oxygen, for 5279 coordination polyhedra and 21 761 bond distances for the metalloid ions, and 1821 coordination polyhedra and 10 723 bond distances for the post-transition metal ions. For the metalloid and post-transition elements with lone-pair electrons, the more common oxidation state between n versus n +2 is n for Sn, Te, Tl, Pb and Bi and n +2 for As and Sb. There is no correlation between bond-valence sum and coordination number for cations with stereoactive lone-pair electrons when including secondary bonds, and both intermediate states of lone-pair stereoactivity and inert lone pairs may occur for any coordination number > [4]. Variations in mean bond length are ∼0.06–0.09 Å for strongly bonded oxyanions of metalloid and post-transition metal ions, and ∼0.1–0.3 Å for ions showing lone-pair stereoactivity. Bond-length distortion is confirmed to be a leading cause of variation in mean bond lengths for ions with stereoactive lone-pair electrons. For strongly bonded cations ( i.e. oxyanions), the causes of mean bond-length variation are unclear; the most plausible cause of mean bond-length variation for these ions is the effect of structure type, i.e. stress resulting from the inability of a structure to adopt its characteristic a priori bond lengths.
Lone pair
Metalloid
Coordination number
Oxidation state
Valence electron
Bond energy
Cite
Citations (78)
We investigate structural parameters, i.e., bond lengths and bond angles of isolated uncapped zigzag single-wall nanotubes in detail. The bond lengths and bond angles are determined for several radii tubes by using a theoretical procedure based on the helical and rotational symmetry for atom coordinates generation, coupled with Tersoff potential for interaction energy calculations. Results show that the structure of zigzag tubes is governed by two bond lengths. One bond length is found to have a value equal to that of graphite, while the other one is larger. Furthermore, the tube length is found to have significant effect only on larger bond length in zigzag tubes. With the application of the pressure, only the larger bond length compresses, the other one remaining practically constant. At some critical pressure, this bond length becomes equal to constant bond length. This behavior of bond lengths is different from those of armchair tubes. An analysis regarding the cross sectional shape has also been done. At some higher pressure, transition from circular to oval cross section takes place. This transition pressure is found to be equal 2.06GPa for (20,0) tube. Some comparison with chiral tubes has also been made and important differences on bond length behavior have been observed.
Zigzag
Molecular geometry
Single bond
Bond energy
Cite
Citations (0)
The crystal structure of [Ni(en)(OH2)4][NO3]2 is reported (en = ethylenediamine). The mean Ni–N bond length is 2.065 A, and N–Ni–N bond angle 83.6°. N–M–N angles in en complexes, and O–M–O angles in acetylacetonates, are discussed in terms of their relation to M–N or M–O bond length. A conformational analysis of tris-en complexes is carried out so as to compare the predicted effect on the N–M–N angle of varying the M–N bond length with the observed relation between N–M–N angle and M–N length.
Ethylene diamine
Molecular geometry
Tetra
Crystal (programming language)
Cite
Citations (21)
A Hartree-Fock optimized geometry for a water molecule in a statistical mechanical Monte Carlo bath of 89 water molecules was determined using a polarization model. Both the O–H bond lengths and ∠HOH bond angle were found to increase from the gas to the liquid phase. The bond length increase is in good agreement with recent neutron diffraction results; liquid water is closer in bond length to gas phase water than ice. In combination with the optimized ∠HOH bond angle approaching tetrahedral, the conclusion is that quadrupole moment dominates the water geometry in the liquid phase.
Molecular geometry
Energy minimization
Cite
Citations (46)