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.

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.

Dipole moments and electronic absorption spectra of aryltricyanoethylenes

1970 ◽  
Vol 66 ◽  
pp. 769 ◽  
Author(s):  
Israel Agranat ◽  
Zvi Rappoport ◽  
Hannah Weiler-Feilchenfeld
Keyword(s):  
Absorption Spectra ◽  
Electronic Absorption ◽  
Electronic Absorption Spectra ◽  
Dipole Moments

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.

scholarly journals THE CHARACTERISTIC FEATURES OF THE ELECTRONIC ABSORPTION SPECTRA AND ELEMENTAL COMPOSITION OF HUMIC ACIDS OF DIFFERENT TYPES AND TYPES OF PEAT KHANTY-MANSIYSK AUTONOMOUS OKRUG - YUGRA

2017 ◽  
Vol 13 (4) ◽  
pp. 7-16
Author(s):  
Evgeniy Mikhailovich Osnitsky ◽  
Oleg Stepanovich Kuzmenko ◽  
Ksenya Valeryevna Dobryakovа ◽  
Davyd Vladimirovich Boroday ◽  
Mikhail Petrovich Sartakov ◽  
...  
Keyword(s):  
Elemental Composition ◽  
Absorption Spectra ◽  
Humic Acids ◽  
Electronic Absorption ◽  
Electronic Spectra ◽  
Electronic Absorption Spectra ◽  
Middle Taiga ◽  
Taiga Zone ◽  
Extinction Coefficients ◽  
Characteristic Features

The article reveals the results of studies of the humic acids electronic spectra for various types and kinds of peat in the middle-taiga zone of Western Siberia (Khanty-Mansiysk Autonomous Okrug - Yugra). It was found that the increase in optical density is observed in samples of humic acids which were extracted from the peat with a high degree of decomposition (40-65 %). At the first approximation the interpretation of received electronic spectra gives reason to range humic acids in the order with increasing proportion of aromatic structures share in macromolecules in the following order: 1) peat humic acids having a degree of expansion from 0 to 35 % with the content of a large number of peat-forming plants, where the extinction coefficients vary from 0.039 to 0.054 or sphagnum peat with the same degree of decomposition with the sphagnum containing 95-100 %, where the extinction coefficients have values between 0.030 and 0.042; 2) humic acids of all types and kinds of peat with a degree up to 35 %, where the extinction coefficients are from 0.042 to 0.068; 3) humic acid of peats of all examined types and species with a degree of decomposition from 40 % to 65 %, where the extinction coefficients vary from 0.059 to 0.087. Although the method of electron spectroscopy is an important tool in the study of humification processes in peat, it has a limited informative value due to unresolved spectra. Thus, peat humic acids with various botanical composition and various degree of decomposition are characterized by similar absorption spectra in the visible area in the form of a monotone increasing of absorption in short wavelength interval and differ from each other only by the absorption intensity. Based on the obtained values of the electronic absorption spectra of the GK and the magnitudes of their degree of benzoindole (α), which are calculated by the results of elemental analysis, the obtained information about the ratio of aromatic and aliphatic fragments in the molecules of humic acids, i.e. the information about the structural organization of the molecule . For the conditions of the Khanty-Mansi Autonomous Okrug - Yugra in all samples of peat humic acids did not reveal the dependence of their elemental composition from the types of source of peat, from the peculiarities of their species caused by the location and the specifics of peat formation.

Electronic absorption spectra and π-electron structure of 2-propenylidene-1,2-dihydropyridine and its derivatives

1979 ◽  
Vol 44 (3) ◽  
pp. 884-894 ◽  
Author(s):  
Josef Kuthan ◽  
Dušan Ilavský ◽  
Jiří Krechl
Keyword(s):  
Absorption Spectra ◽  
Satisfactory Agreement ◽  
Electronic Absorption ◽  
Heterocyclic System ◽  
Electronic Absorption Spectra ◽  
Electron Structure ◽  
Ultraviolet Region ◽  
Near Ultraviolet ◽  
Experimental Absorption

The results of the PPP calculations of the singlet-singlet transitions of 1-methyl-3'-cyano-3'-alkoxycarbonyl-2-propenylidene-1,2-dihydropyridines II and 1-methyl-4-amino-3,3'-dicyano-3',5-di(methoxycarbonyl)-2-propenylidene-1,2-dihydropyridine (III) are in a satisfactory agreement with the experimental absorption curves in the visible and near ultraviolet region. Based on this finding, the absorption of the parent heterocyclic system of 2-propenylidene-1,2-dihydropyridine (I) is predicted. Some aspects of the π-electron structure of the substances I-III in the S0, S1 S2 and states are discussed.

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