Photocolouration of 2,4,4,6-Tetraaryl-4H-thiopyrans: A Semiempirical Quantum Chemical Study

1994 ◽  
Vol 59 (5) ◽  
pp. 1115-1125 ◽  
Author(s):  
Stanislav Böhm ◽  
Pavel Šebek ◽  
Stanislav Nešpůrek ◽  
Josef Kuthan
Keyword(s):  
Absorption Spectra ◽  
Electronic Absorption ◽  
Quantum Chemical ◽  
Electronic Absorption Spectra ◽  
Quantum Chemical Study ◽  
Theoretical Data ◽  
Chemical Study ◽  
Pm3 Method ◽  
Uv Illumination

Molecular geometries of 4H-thiopyrans Ia, Ib and their possible photoisomers IVa - VIIa and IVb - VIIb were optimized by the AM1 and PM3 method and used for the calculation of electronic absorption spectra by the CNDO/S-CI procedure. Comparison of the theoretical data with experimental UV-VIS absorption spectra made it possible to postulate two probable mechanisms of the photocolouration of Ia, Ib caused by sunlight or UV-illumination.

Photocolouration of 2,4,4,6-Tetraaryl-1,4-dihydropyridines: A Semiempirical Quantum Chemical Study

1994 ◽  
Vol 59 (2) ◽  
pp. 262-272 ◽  
Author(s):  
Stanislav Böhm ◽  
Michal Hocek ◽  
Stanislav Nešpůrek ◽  
Josef Kuthan
Keyword(s):  
Absorption Spectra ◽  
Electronic Absorption ◽  
Quantum Chemical ◽  
Spectroscopic Data ◽  
Electronic Absorption Spectra ◽  
Quantum Chemical Study ◽  
Chemical Study ◽  
Probable Mechanism ◽  
Pm3 Method ◽  
Uv Illumination

Molecular geometries of 1,4-dihydropyridines Ia, Ib and their possible photoisomers IIa - Va and IIb - Vb were optimized by the PM3 method. The electronic absorption spectra were calculated by the CNDO/S-CI procedure and compared with the experimental spectroscopic data. A probable mechanism of the photocolouration of Ia, Ib, caused by sunlight or UV illumination, is proposed, and structures IIIa, IIIb are assigned to violet or green coloured species.

Photocolouration of 2,4,4,6-Tetraaryl-4H-pyrans and Their Heteroanalogues: Importance of Hypervalent Photoisomers

1995 ◽  
Vol 60 (10) ◽  
pp. 1621-1633 ◽  
Author(s):  
Stanislav Böhm ◽  
Mojmír Adamec ◽  
Stanislav Nešpůrek ◽  
Josef Kuthan
Keyword(s):  
Reaction Kinetics ◽  
Absorption Spectra ◽  
Electronic Absorption ◽  
Electronic Absorption Spectra ◽  
Theoretical Data ◽  
Order Reaction ◽  
Bleaching Process ◽  
First Order ◽  
Photodegradation Products ◽  
Hypervalent Molecules

Molecular geometries of 2,4,4,6-tetraphenyl-4H-pyran (Ia), 4,4-(biphenyl-2,2e-diyl)-2,6-diphenyl-4H-pyran (Ib) and their heterocyclic isomers II-V were optimized by the PM3 method and used for the calculation of electronic absorption spectra by the CNDO/S-CI procedure. Comparison of the theoretical data with experimental UV-VIS absorption spectra made possible to select hypervalent molecules IIIa, IIIb, IVa and IVb being responsible for the photocolouration of 4H-pyrans Ia, Ib, while compounds Va, Vb, VI and VII come into account as possible photodegradation products. The bleaching process of the UV illuminated compound Ia is analyzed in terms of dispersive first-order reaction kinetics.

Electronic spectroscopy of ethyl bromide probed by VUV photoabsorption and quantum chemical calculations

2017 ◽  
Vol 19 (9) ◽  
pp. 6454-6469 ◽  
Author(s):  
Aparna Shastri ◽  
Param Jeet Singh ◽  
Sunanda Krishnakumar ◽  
Asim Kumar Das ◽  
B. N. Raja Sekhar
Keyword(s):  
Synchrotron Radiation ◽  
Quantum Chemical Calculations ◽  
Absorption Spectra ◽  
Electronic Absorption ◽  
Quantum Chemical ◽  
Electronic Absorption Spectra ◽  
Electronic Spectroscopy ◽  
Ethyl Bromide ◽  
Tddft Calculations ◽  
Comprehensive Study

A comprehensive study of the electronic absorption spectra of C2H5Br and C2D5Br using synchrotron radiation photoabsorption spectroscopy and TDDFT calculations.

Electronic absorption spectra of imidazolium-based ionic liquids studied by far-ultraviolet spectroscopy and quantum chemical calculations

2016 ◽  
Vol 18 (32) ◽  
pp. 22526-22530 ◽  
Author(s):  
Ichiro Tanabe ◽  
Yuji Kurawaki ◽  
Yusuke Morisawa ◽  
Yukihiro Ozaki
Keyword(s):  
Ionic Liquids ◽  
Quantum Chemical Calculations ◽  
Absorption Spectra ◽  
Electronic Absorption ◽  
Quantum Chemical ◽  
Electronic Absorption Spectra ◽  
Ultraviolet Spectroscopy ◽  
Deep Ultraviolet ◽  
Far Ultraviolet

Electronic absorption spectra of imidazolium-based ionic liquids were studied by far- and deep-ultraviolet spectroscopy and quantum chemical calculations.

Electronic absorption spectra and dipole moments of diazafluoren-9-ones studied by the MIM, PPP, and CNDO/2 methods

1976 ◽  
Vol 54 (12) ◽  
pp. 1870-1874 ◽  
Author(s):  
Concetta Gandolfo ◽  
Giuseppe Buemi ◽  
Domenico Grasso ◽  
Salvatore Fasone
Keyword(s):  
Absorption Spectra ◽  
Satisfactory Agreement ◽  
Electronic Absorption ◽  
Electronic Spectra ◽  
Benzene Solution ◽  
Electronic Absorption Spectra ◽  
Dipole Moments ◽  
Theoretical Data ◽  
Uv Spectra

The electronic spectra of three diazafluoren-9-one isomers have been measured in cyclohexane solution and the results compared with those of 'molecules in molecules'(MIM) and PPP calculations. A satisfactory agreement between experimental and theoretical data has been found, and five π → π* transitions can be assigned to their uv spectra. For two compounds dipole moments in benzene solution have been measured and results are compared with theoretical values obtained by MIM and CNDO/2 calculations.

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