The electronic absorption spectra of some coumarins. A molecular orbital treatment

1985 ◽  
Vol 63 (6) ◽  
pp. 1173-1179 ◽  
Author(s):  
Rafie H. Abu-Eittah ◽  
Bahgat Ali H. El-Tawil
Keyword(s):  
Absorption Spectra ◽  
Molecular Orbital ◽  
Electronic Absorption ◽  
Transition Energy ◽  
Electronic Absorption Spectra ◽  
Band Intensity ◽  
Molecular Orbital Calculations ◽  
Atomic Orbitals ◽  
Experimental Transition

The electronic absorption spectra of coumarin and its derivatives umbelliferone (6-hydroxycoumarin), esculetin (6,7-dihydroxycoumarin), and scopoletin (6-methoxy-7-hydroxycoumarin) were investigated. The n → π* transition was not observed in the spectrum of coumarin but was observed in the spectra of some of its derivatives. Molecular orbital calculations, using the INDO procedures, were carried out on coumarin and some of its derivatives. The activities of the different sites of the molecules are discussed in terms of the coefficients of the atomic orbitals constituting the HOMO and the LUMO. The correspondence between the calculated and experimental transition energy and band intensity is satisfactory.

The electronic absorption spectra of some N-sulfinylanilines. A molecular orbital treatment

1997 ◽  
Vol 75 (7) ◽  
pp. 934-941 ◽  
Author(s):  
R. Abu-Eittah ◽  
H. Moustafa ◽  
A.M. Al-Omar
Keyword(s):  
Absorption Spectra ◽  
Molecular Orbital ◽  
Electron Acceptor ◽  
Electronic Absorption ◽  
Electronic Absorption Spectra ◽  
Basis Sets ◽  
Theoretical Treatment ◽  
Molecular Orbital Calculations ◽  
Strong Electron ◽  
Anti Conformer

The electronic absorption spectra of N-sulfinylaniline and some of its derivatives were investigated using different solvents. The spectral behavior of the molecules indicated their planarity and that the NSO group is a strong electron acceptor. All the observed bands correspond to delocalized π → π* transitions; n → π* transition were not observed as discrete bands. Ab initio molecular orbital calculations were performed using four different basis sets. The results showed that the NSO group is nonlinear, the molecules studied are planar, and the syn conformer is more stable than the anti conformer. Keywords: N-sulfinylanilines, spectra and theoretical treatment.

The Electronic Absorption Spectra of Some N-Substituted Pyrroles—Molecular Orbital Calculations

1982 ◽  
Vol 36 (3) ◽  
pp. 297-301 ◽  
Author(s):  
R. Abu-Eittah ◽  
R. Hilal ◽  
M. S. El-Shall
Keyword(s):  
Absorption Spectra ◽  
Molecular Orbital ◽  
Electronic Absorption ◽  
Electronic Transition ◽  
Electronic Absorption Spectra ◽  
Experimental Results ◽  
Electronic Transitions ◽  
Molecular Orbital Calculations ◽  
Nonpolar Solvents ◽  
State Functions

The electronic absorption spectra of N-phenylpyrrole and some of its parasubstituted derivatives have been investigated in polar and nonpolar solvents. Such an investigation could predict the extent of resonance interaction between the pyrryl and phenyl moieties of the composite molecule. The direction and polarization of the electronic transitions were predicted. Molecular orbital calculations using the SCF-CI procedures were performed on N-phenylpyrrole and some of its p-substituted derivatives. The state functions and energies were computed. The weight of each configuration was evidence for the direction of the electronic transition. The correspondence between the theoretical and experimental results is satisfactory.

scholarly journals Electronic Absorption Spectra of Some Triazolopyrimidine Derivatives

2011 ◽  
Vol 2011 ◽  
pp. 1-8 ◽  
Author(s):  
Hussein Moustafa ◽  
M. F. Shibl ◽  
Rifaat Hilal ◽  
Laila I. Ali ◽  
Sheimaa Abdel Halim
Keyword(s):  
Charge Transfer ◽  
Absorption Spectra ◽  
Electronic Absorption ◽  
Electronic Absorption Spectra ◽  
Dipole Moments ◽  
Molecular Orbital Calculations ◽  
Transition Energies ◽  
Density Distributions ◽  
Nonpolar Solvents ◽  
Experimental Transition

The electronic absorption spectra of triazolo pyrimidine and some of its derivatives were measured in polar as well as nonpolar solvents. Assignment of the observed transitions is facilitated via molecular orbital calculations. Charge density distributions, dipole moments, and the extent of delocalization of the MOS were used to interpret the observed solvent effects. The observed transitions are assigned as charge transfer (CT), localized, and delocalized according to the contribution of the various configurations in the CI-states. The correspondence between the calculated and experimental transition energies is satisfactory.

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