Quantum-chemical study of photochemical E-Z isomerization of methanimine and its fluoro derivatives

1985 ◽  
Vol 50 (6) ◽  
pp. 1283-1290
Author(s):  
Peter Ertl ◽  
Jaroslav Leška
Keyword(s):  
Singlet State ◽  
Quantum Chemical Study ◽  
Chemical Study ◽  
Radiative Transition ◽  
Reaction Paths ◽  
Excited Singlet ◽  
Optimization Of Geometry ◽  
Full Optimization ◽  
Franck Condon ◽  
Fluoro Derivatives

The CNDO/2 CI method has been used for full optimization of geometry of methanimine and its fluoro derivatives in the first excited singlet state (S1). The reaction paths of the photochemical E-Z isomerization of these molecules in the S1 state by inversion and rotation mechanisms have been studied by the method of reaction coordinate with full optimization of all other coordinates. Each of the two mechanisms mentioned goes through an energy minimum, the rotation minimum being deeper. The non-radiative transition from the rotation minimum in the S1 state to the corresponding Franck-Condon ground state enables the isomerization of the molecule. The reaction paths obtained are similar to, and the energy differences of the corresponding Franck-Condon states are close to or identical with results of the model ab initio calculations published by other authors.

A quantum-chemical study of structure of H3O+ in electronically excited states

1986 ◽  
Vol 51 (4) ◽  
pp. 738-745 ◽  
Author(s):  
Peter Ertl ◽  
Jaroslav Leška
Keyword(s):  
Quantum Chemical Study ◽  
Chemical Study ◽  
Electronic Distribution ◽  
Singlet States ◽  
Electronically Excited ◽  
Electron Distributions ◽  
Optimization Of Geometry ◽  
Full Optimization ◽  
Excited Singlet States ◽  
Almost All

The CNDO/2-Cl method has been used for full optimization of geometry of the H3O+ ion in all its electronically excited singlet states and for calculation of electron distribution. The electronic structure shows that H3O+ in almost all states exhibits lower tendency to split off the proton than it does in the ground state. For the first excited state the geometries and electron distributions of the isoelectronic set H3O+, NH3, CH-3 have been calculated by the INDO-Cl method in the triplet state, too. The particles only have slightly different geometry and electronic distribution from those of the first singlet state.

A quantum-chemical study of dehydration of ortho forms of formaldehyde and formic acid

1986 ◽  
Vol 51 (9) ◽  
pp. 1819-1833 ◽  
Author(s):  
Jaroslav Leška ◽  
Eugen Németh ◽  
Dušan Loos
Keyword(s):  
Oxygen Atom ◽  
Water Molecule ◽  
Formic Acid ◽  
Gas Phase ◽  
Quantum Chemical ◽  
Quantum Chemical Study ◽  
Chemical Study ◽  
Reaction Paths ◽  
Full Optimization ◽  
Acid Catalyzed

Gas-phase dehydration of methanediol (I) and methanetriol (II) has been studied by the MINDO/3 method with full optimization of the reaction paths. The intramolecular dehydration goes via high barriers (I 257.4, II 193.3 kJ mol-1). The acid-catalyzed dehydration involving protonation at oxygen atom of I goes via a considerably lower barrier (63.3 kJ mol-1), whereas protonation at oxygen atom of II results in practically spontaneous dehydration (0.4 kJ mol-1), which is the reason for the formic acid not being hydrated in water. Deprotonation of the protonated formaldehyde (II) and protonated formic acid (IV) is connected with high barriers (429.1 and 523.0 kJ mol-1, resp.). The deprotonation by a water molecule added to III and IV involves substantially lower barriers (53.9 and 96.3 kJ mol-1, resp.).

An ab initio quantum chemical study of vertically excited singlet states of pyrimidine

1992 ◽  
Vol 162 (2-3) ◽  
pp. 359-367 ◽  
Author(s):  
Per-Åke Malmqvist ◽  
Björn O. Roos ◽  
Markus P. Fülscher ◽  
Alistair P. Rendell
Keyword(s):  
Ab Initio ◽  
Quantum Chemical ◽  
Quantum Chemical Study ◽  
Chemical Study ◽  
Excited Singlet ◽  
Singlet States ◽  
Excited Singlet States

Die Schwingungsstruktur der Shpolskii-Spektren von Anthracen, 9-Methyl-und 9,10-Dimethylanthracen in n-Hexan bei 77 K. I. Fluoreszenz / The Vibronic Structure of Shpolskii Spectra of Anthracene, 9-Methyl- and 9,10-Dimethylanthracene in n-Hexane at 77 K I. Fluorescene

1979 ◽  
Vol 34 (1) ◽  
pp. 105-113 ◽  
Author(s):  
Ch. Jung ◽  
A. Kawski ◽  
M. I. Żukowska
Keyword(s):  
Fluorescence Spectra ◽  
Singlet State ◽  
Methyl Groups ◽  
Excited Singlet ◽  
Normal Coordinates ◽  
Pi Method ◽  
Out Of Plane ◽  
Condon Factors ◽  
Franck Condon ◽  
Equilibrium Geometries

Abstract The fluorescence spectra of anthracene, 9-methyl- and 9,10-dimethylanthracene in n-hexane at 77 K were measured. The Franck-Condon-Factors are evaluated using equilibrium geometries, vibrational frequencies and normal coordinates of the molecules in the ground and first excited singlet state which were calculated by the QCFF/PI-method. These results are then compared with experimentally determined frequencies and estimated intensities. The new vibronic lines in the fluorescence spectra of the methylated anthracenes correspond to totally symmetric vibrations, up to 1000 cm-1 originated mostly by mixing with out-of-plane vibrations of the atoms of the anthracene skeleton. Above 1000 cm-1 these vibrations which have greater projections of their normal coordinates on the internal coordinates of the methyl groups, are not visible as vibronic lines in the fluorescence spectra. The multiplet structures of the O-O-transitions are ascertained.

The Gold Porphyrin First Excited Singlet State¶

2002 ◽  
Vol 76 (1) ◽  
pp. 47 ◽  
Author(s):  
Joakim Andréasson ◽  
Gerdenis Kodis ◽  
Su Lin ◽  
Ana L. Moore ◽  
Thomas A. Moore ◽  
...  
Keyword(s):  
Singlet State ◽  
Excited Singlet State ◽  
Excited Singlet
Sign in / Sign up

Export Citation Format

Share Document