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-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 Enstatite (MgSiO3) and forsterite (Mg2SiO4) monomers and dimers: highly detectable infrared and radioastronomical molecular building blocks

2019 ◽  
Vol 492 (1) ◽  
pp. 276-282 ◽  
Author(s):  
E Michael Valencia ◽  
Charlie J Worth ◽  
Ryan C Fortenberry
Keyword(s):  
Small Molecules ◽  
Quantum Chemical ◽  
Spectroscopic Data ◽  
Dipole Moments ◽  
Quantum Chemical Study ◽  
Building Blocks ◽  
Chemical Study ◽  
High Energy ◽  
Molecular Building Blocks ◽  
High Level

ABSTRACT Isolated MgSiO3 and Mg2SiO4 molecules are shown here to exhibit bright infrared (IR) features that fall close to unattributed astronomical lines observed toward objects known to possess crystalline enstatite and forsterite, minerals of the same respective empirical formulae. These molecules are therefore tantalizing candidates for explaining the origin of such features. Furthermore, the C2v monomer minima of each formula set have dipole moments on the order of 10.0 D or larger making them desirable candidates for radioastronomical observation as enabled through rotational spectroscopic data further provided in this high-level CCSD(T)-F12/cc-pVTZ-F12 quantum chemical study. Astrophysical detection of these molecules could inform the build-up pathways for creating nanocrystals from small molecules in protoplanetary discs or could show the opposite in explaining the destruction of enstatite and forsterite minerals in supernovae events or other high-energy stellar processes. This work also shows that the lowest energy isomers for molecules containing the geologically necessary elements Mg and Si have oxygen bonded between any of the other heavier elements making oxygen the glue for pre-mineralogic chemistry.

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.

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