ChemInform Abstract: Ab initio Molecular Orbital Calculations on LiPO2 and LiClO2 Charge-Transfer Complexes: Geometries and Vibrational Frequencies.

ChemInform ◽  
1990 ◽  
Vol 21 (47) ◽  
Author(s):  
F. RAMONDO ◽  
L. BENCIVENNI
Keyword(s):  
Charge Transfer ◽  
Ab Initio ◽  
Molecular Orbital ◽  
Vibrational Frequencies ◽  
Charge Transfer Complexes ◽  
Molecular Orbital Calculations

Analysis of molecular polarizabilities and polarizability derivatives in H2, N2, F2, CO, and HF, with the theory of atoms in molecules

1996 ◽  
Vol 74 (6) ◽  
pp. 1139-1144 ◽  
Author(s):  
Kathleen M. Gough ◽  
Margaret M. Yacowar ◽  
Richard H. Cleve ◽  
Jason R. Dwyer
Keyword(s):  
Charge Transfer ◽  
Ab Initio ◽  
Molecular Orbital ◽  
Atoms In Molecules ◽  
Molecular Polarizability ◽  
Molecular Orbital Calculations ◽  
Induced Dipole ◽  
Order Of Magnitude ◽  
Atomic Dipole ◽  
Molecular Polarizabilities

Ab initio molecular orbital calculations have been performed on the title molecules at the SCF-HF and MP2 levels to obtain molecular polarizabilities and the derivatives associated with bond stretch. The wave functions from these calculations have been analyzed with the theory of atoms in molecules (AIM). Both the polarizability and its derivative are successfully reconstructed from AIM terms representing the transfer of charge between atoms (CT = charge transfer) and the rearrangement of charge within an atomic basin (AD = atomic dipole). The results for the diatomics are compared to each other and to the alkanes studied previously. Equilibrium polarizabilities are qualitatively explained with reference to atomic electronegativity and type of bonding. While derivatives of the mean molecular polarizability differ by a factor of two at most, individual contributions vary by an order of magnitude. The derivatives along the bond axis for H2 are ΔCT = 2.06 and ΔAD = −0.62 × 10−30 C m/V, while for N2 they are ΔCT = 13.77 and ΔAD = −10.00 × 10−30 C m/V. The common feature observed is that as the induced dipole due to charge transfer increases, the induced dipole due to changes in the atomic dipole also increases and opposes it. Key words: diatomic molecules, molecular polarizability, molecular polarizability derivative, theory of atoms in molecules, ab initio molecular orbital calculations.

Photochemical reactions of charge-transfer complexes. III. Molecular orbital studies of the charge-transfer complexes between 1,2-dimethoxyethylenes and 1,2-dicyanoethylenes

1981 ◽  
Vol 59 (6) ◽  
pp. 974-981 ◽  
Author(s):  
Po Cheong Wong ◽  
Russell J. Boyd
Keyword(s):  
Charge Transfer ◽  
Ab Initio ◽  
Molecular Orbital ◽  
Photochemical Reactions ◽  
Charge Transfer Complexes ◽  
Double Bonds ◽  
Mo Calculations ◽  
Model Compounds ◽  
Projected Distance

Ab initio and PCILO molecular orbital (MO) calculations for the four π–π* charge-transfer complexes formed between maleonitrile (MN) and fumaronitrile (FN), and cis (CS) and trans-1,2-dimethoxyethyIene (TR) are reported. The donor and the acceptor molecules are stacked in parallel planes. Trans and cis-l,2-dihydroxyethylene are used as the model compounds for TR and CS in the determination of the optimum geometries of the complexes. Both types of MO calculations indicate that the eclipsed geometry (with the two central double bonds parallel and the centres of the double bonds centred over one another) is relatively unstable. With limited geometry searching, we find that the slipped geometry (with the two central double bonds parallel but separated at a projected distance of 2.2 Å and the oxygen atoms above the cyanocarbon atoms) is the preferred structure. According to the ab initio calculations the relative order of the calculated heats of formation (ΔHθ's) for these complexes is: MN−CS > FN−CS > FN−TR > MN−TR.

A pairwise additivity scheme for conformational energies of substituted ethanes

1975 ◽  
Vol 343 (1632) ◽  
pp. 1-10 ◽  
Keyword(s):  
Large Deviations ◽  
Ab Initio ◽  
Dihedral Angle ◽  
Molecular Orbital ◽  
Methyl Groups ◽  
Molecular Orbital Calculations ◽  
Linear Combinations ◽  
Strongly Interacting ◽  
Conformational Energies

Ab initio molecular orbital calculations are used to explore additivity in the conformational energies of poly-substituted ethanes in terms of conformational energies of ethane and appropriate mono- and 1,2-di-substituted derivatives. Such relations would allow complex calculations for poly-substituted ethanes to be replaced by much simpler ones on a small number of parent molecules. General expressions for the linear combinations are derived from the assumption that interactions between vicinal substituents are pairwise additive and depend only on the vicinal dihedral angle. The additivity scheme is tested for 15 ethanes, di-, tri- or tetrasubstituted by cyano and methyl groups and for a smaller number of fluoroethanes. Additivity applies to within 0.1- 0.3 k J mol -1 in the methylethanes and mostly to within about 0.7- 0.8 kJ mol -1 in cyanoethanes. Large deviations are found among the geminally substituted fluoroethanes. It is suggested that the additivity approximation is most successful in the absence of strongly interacting geminal groups. Predictions are made of conformational energies of ten hexa(cyano- and methyl-) substituted ethanes.

Gas-Phase Tautomerism in the Triazoles and Tetrazoles: A Study by Photoelectron Spectroscopy and ab Initio Molecular Orbital Calculations

1981 ◽  
Vol 36 (11) ◽  
pp. 1246-1252 ◽  
Author(s):  
Michael H. Palmer ◽  
Isobel Simpson ◽  
J. Ross Wheeler
Keyword(s):  
Ab Initio ◽  
Gas Phase ◽  
Molecular Orbital ◽  
Photoelectron Spectroscopy ◽  
Relative Stability ◽  
Photoelectron Spectra ◽  
Equilibrium Geometry ◽  
Molecular Orbital Calculations ◽  
Methyl Derivatives

The photoelectron spectra of the tautomeric 1,2,3,- and 1,2,4-triazole and 1,2,3,4-tetrazole systems have been compared with the corresponding N-methyl derivatives. The dominant tautomers in the gas phase have been identified as 2 H-1,2,3-triazole, 1 H-1,2,4-triazole and 2H-tetrazole.Full optimisation of the equilibrium geometry by ab initio molecular orbital methods leads to the same conclusions, for relative stability of the tautomers in each of the triazoles, but the calculations wrongly predict the tetrazole tautomerism.

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