scholarly journals Analysis of One-Bond Se-Se Nuclear Couplings in Diselenides and 1,2-Diselenoles on the Basis of Molecular Orbital Theory: Torsional Angular Dependence, Electron Density Influence, and Origin inJ1(Se, Se)

2009 ◽  
Vol 2009 ◽  
pp. 1-9 ◽  
Author(s):  
Akito Tanioku ◽  
Satoko Hayashi ◽  
Waro Nakanishi
Keyword(s):  
Electron Density ◽  
Molecular Orbital ◽  
Angular Dependence ◽  
Basis Sets ◽  
Molecular Orbital Theory ◽  
Spin Orbit ◽  
Slater Type ◽  
Orbital Theory ◽  
Derivatives Of ◽  
Mo Theory

Nuclear couplings for the Se-Se bonds,J1(Se, Se), are analyzed on the basis of the molecular orbital (MO) theory. The values are calculated by employing the tripleζbasis sets of the Slater type at the DFT level.J1(Se, Se)are calculated modeled by MeSeSeMe (1a), which shows the typical torsional angular dependence onϕ(CMeSeSeCMe). The dependence explains well the observedJ1(Se, Se)obsdof small values (≤64 Hz) forRSeSeR′(1) (simple derivatives of1a) and large values (330–380 Hz) observed for 4-substituted naphto[1,8-c,d]-1,2-diselenoles (2) which correspond tosymperiplanardiselenides.J1(Se, Se :2) becomes larger as the electron density on Se increases. The paramagnetic spin-orbit terms contribute predominantly. The contributions are evaluated separately from each MO(ψi)and eachψi→ψatransition, whereψiandψaare occupied and unoccupied MO's, respectively. The separate evaluation enables us to recognize and visualize the origin and the mechanism of the couplings.

Molecular Orbitals and CH3, CH2, and CH Deformation Group Frequencies

1980 ◽  
Vol 34 (1) ◽  
pp. 1-6 ◽  
Author(s):  
Norman B. Colthup
Keyword(s):  
Linear Relationship ◽  
Electron Density ◽  
Force Constant ◽  
Molecular Orbital ◽  
Interaction Force ◽  
Molecular Orbitals ◽  
Deformation Vibration ◽  
Molecular Orbital Theory ◽  
Orbital Theory ◽  
Symmetrical Deformation

A linear relationship has been found between the wavenumber of the CH3 symmetrical deformation vibration and the electron density on the CH3 carbon as calculated from CNDO/2 molecular orbital theory. Other CH deformation vibrations are also related to the electron density on the carbon and, as a result, can be correlated with the CH3 symmetrical deformation wavenumber. These include ν̄(CH2 def), ν̄(CH2 wag) and both components of ν̄(CH wag). The splitting of ν̄(CH3 sym def) in isopropyl and t-butyl groups has long been known. It is shown here that the effect is due to an interaction force constant relating to the CH3 symmetrical deformation vibrations of two or three different neighboring CH3 groups. The origin of the interaction is thought to be an H,H′ repulsion between hydrogens on the different CH3 groups.

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