Ab initio molecular orbital calculations of the internal rotation of styrene with electron correlation using the polarized 6-31G* basis set

1990 ◽  
Vol 94 (16) ◽  
pp. 6175-6179 ◽  
Author(s):  
Seiji. Tsuzuki ◽  
Kazutoshi. Tanabe ◽  
Eiji. Osawa
Keyword(s):  
Ab Initio ◽  
Internal Rotation ◽  
Molecular Orbital ◽  
Electron Correlation ◽  
Basis Set ◽  
Molecular Orbital Calculations

Structures of simple anions from ab initio molecular orbital calculations

1976 ◽  
Vol 29 (8) ◽  
pp. 1635 ◽  
Author(s):  
L Radom
Keyword(s):  
Ab Initio ◽  
Molecular Orbital ◽  
Basis Set ◽  
Basis Sets ◽  
Molecular Orbital Calculations ◽  
Limited Information ◽  
Orbital Theory ◽  
Comparable Quality ◽  
Split Valence ◽  
Theoretical Results

Ab initio molecular orbital theory with the minimal STO-3G and split-valence 4-31G basis sets is used to obtain geometries of 18 anions:OH-, NH2-, HF2-, BH4-, BF4-, C22-, CN-, NCN2-, N3-, NO2-, NO3-, 0CCO2-, CO32-, HCOO-, CH3COO-, C2O42-, C4O42- and C(CN)3-. The theoretical results are compared with experimental results from the literature. The STO-3G basis set performs somewhat worse for anions than for neutral molecules. On the other hand, the 4-31G basis set gives good results and predicts bond lengths to within 0.02� for all the molecules considered. Limited information on bond angle predictions suggests that these are of comparable quality to those for neutral molecules. The tricyanomethanide ion is predicted to be planar.

Molecular Orbital Calculations of Cu-Halides

1981 ◽  
Vol 36 (10) ◽  
pp. 1095-1099 ◽  
Author(s):  
H. Itoh
Keyword(s):  
Ab Initio ◽  
Molecular Orbital ◽  
Energy Levels ◽  
Basis Set ◽  
Orbital Energy ◽  
Ionic Character ◽  
Molecular Orbital Calculations ◽  
Ab Initio Hf ◽  
Mo Theory

An ab initio HF MO theory is applied to CuX, CuX2 (X = F and Cl) and (CuCl)3 . Although the detailed sequence of energy levels depends upon the basis set used, high-lying orbital energy levels have largely halogen p-like character, whereas low-lying orbital energy levels have largely Cu 3 d-like character. This is in agreement with the chemical intuition of a highly ionic character of these compounds.

scholarly journals The para substituent dependence of the internal rotational barrier in benzenethiol

1977 ◽  
Vol 55 (3) ◽  
pp. 552-556 ◽  
Author(s):  
Ted Schaefer ◽  
William J. E. Parr
Keyword(s):  
Ab Initio ◽  
Internal Rotation ◽  
Molecular Orbital ◽  
Rotational Barrier ◽  
Coupling Constants ◽  
Spin Coupling ◽  
Molecular Orbital Calculations ◽  
Fluorine Nucleus ◽  
Spin Coupling Constants ◽  
Spin Spin Coupling

On the basis of the observed spin–spin coupling constants between the sulfhydryl and ring protons and a hindered rotor treatment of the twofold barrier to internal rotation in a series of para substituted benzenethiol derivatives, it is argued that V2 is essentially zero in p-amino-benzenethiol and is 2.5 ± 0.2 kcal/mol in p-nitrobenzenethiol; having intermediate values for the methoxy, fluoro, methyl, and bromo derivatives in solution. The results are based on an assumed relationship between the four-bond and the fictitious six-bond couplings to the sulfhydryl proton. The conclusions are consistent with the observed magnitudes of the couplings over six and seven bonds, respectively, between the sulfhydryl proton and the fluorine nucleus and the methyl protons in the appropriate derivatives; as well as with the coupling between the sulfhydryl and methyl protons in 4-bromo-3-methylbenzenethiol. The experimental barriers are compared with ab initio molecular orbital calculations of their substituent dependence.

Halogen...O(Nitro) Supramolecular Synthon in Crystal Engineering: A Combined Crystallographic Database and Ab Initio Molecular Orbital Study

1997 ◽  
Vol 53 (6) ◽  
pp. 1006-1016 ◽  
Author(s):  
F. H. Allen ◽  
J. P. M. Lommerse ◽  
V. J. Hoy ◽  
J. A. K. Howard ◽  
G. R. Desiraju
Keyword(s):  
Ab Initio ◽  
Molecular Orbital ◽  
Crystal Engineering ◽  
Basis Set ◽  
Molecular Orbital Calculations ◽  
Model Dimer ◽  
Experimental Crystal ◽  
Van Der Waals Radii ◽  
Experimental Crystal Structure ◽  
Intermolecular Perturbation Theory

Crystallographic data for 309 C—X...O(nitro)—C, X = Cl, Br, I, interactions, involving 245 symmetry-independent X atoms, have been investigated out to 0.2 Å above van der Waals radii limits [\nu(O) + \nu(X)]. A total of 138 (45%) of these interactions are shorter than \nu(O) + \nu(X), with the degree of interpenetration of the X and O atoms increasing in the order Cl < Br < I. The analysis also shows that: (a) the C—X...O angle tends to linearity as the X...O distance shortens, (b) the angle of approach of X to the C—NO2 plane is preferentially less than 45° for Cl, with an increasing tendency to in-plane X approach in the order Cl < Br < I, and (c) the halogen (X) forms either (i) mono-coordinate interactions with one nitro O atom, with X...O in a cis relationship to the nitro C substituent about the N—O bond, or (ii) approaches both nitro O atoms in a bifurcated manner; the tendency to form such bifurcated motifs increases in the order Cl < Br < I. Only iodine consistently forms short interactions with both nitro O atoms. Ab-initio-based molecular orbital calculations, using intermolecular perturbation theory (IMPT) applied to a nitromethane–1-chloro-2-methylacetylene model dimer, agree with the analysis of experimental crystal structure geometries. The IMPT calculations yield an attractive interaction energy of ca −6 kJ mol−1 for Cl...O at the 6-31G* basis set level. Calculations for Br...O at the (only available) [6s4p1d] basis set level indicate that this interaction is more attractive than Cl...O.

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