Conformational changes accompanying electronic excitation of trifluoronitrosomethane

1976 ◽  
Vol 54 (16) ◽  
pp. 2658-2668 ◽  
Author(s):  
R. D. Gordon ◽  
S. C. Dass ◽  
J. R. Robins ◽  
H. F. Shurvell ◽  
R. F. Whitlock
Keyword(s):  
Absorption Spectrum ◽  
Excited State ◽  
Gas Phase ◽  
Conformational Changes ◽  
Ground State ◽  
Electronic Excitation ◽  
Excited Electronic State ◽  
Vibrational Structure ◽  
The Other ◽  
Transition Analysis

The 690 nm absorption spectrum of CF3NO has been studied in the gas phase at various temperatures and in the condensed phase at 77 K, and assigned to an (nπ*) transition. Analysis of the vibrational structure shows that, while only the eclipsed conformer is stable in the ground state, there are two stable isomers of comparable energy in the excited electronic state. One has an eclipsed conformation, but with the CF3 group tilted away from the oxygen atom. The other has a staggered conformation. In both of the excited state isomers the barrier to internal rotation is higher than in the ground state.

scholarly journals Solvent-Dependent Resonance Raman Excitation Profiles of 9,9'-Bianthryl

1999 ◽  
Vol 19 (1-4) ◽  
pp. 51-56
Author(s):  
Gregory D. Scholes ◽  
Thierry Fournier ◽  
David Phillips ◽  
Anthony W. Parker
Keyword(s):  
Excited State ◽  
Charge Transfer ◽  
Ground State ◽  
Electronic Excitation ◽  
Electronic Absorption Spectra ◽  
Excited Electronic State ◽  
Resonance Raman ◽  
Initial State ◽  
Solvent Environment ◽  
Raman Excitation Profiles

Dynamics subsequent to the electronic excitation of 9,9′-bianthryl produce a polar emissive excited state for which the symmetry of the bichromophore is broken by a dynamic solvent stabilisation of one of the two, otherwise degenerate, charge transfer configurations which contribute to the excited electronic state. The initial state created upon excitation is examined here by analysis of ground state resonance Raman excitation profiles (REPs) and electronic absorption spectra in solvents of various polarities. The results suggest that the REPs are signalling electronic differences between the initially excited state in the various solvents. We suggest that this is related to the bianthryl excited state being responsive to the disordered solvent environment.

The 5515 Å electronic transition and the geometric structure of s -tetrazine

1968 ◽  
Vol 302 (1469) ◽  
pp. 271-284 ◽  
Keyword(s):  
Molecular Structure ◽  
Absorption Spectrum ◽  
Excited State ◽  
Ground State ◽  
Electronic Excitation ◽  
Visible Region ◽  
Electron Theory ◽  
X Ray ◽  
Isotopic Species

The electronic absorption spectrum of gaseous s -tetrazine (H 2 C 2 N 4 ) in the visible region has been examined under high resolution, and rotational analyses of the J -structure have been performed for bands of six isotopic species. The results have permitted the determination of the molecular structure of s -tetrazine, both in the 1 A g ground state and in the A ~ 1 B 3 u excited state. The s -tetrazine molecule in its ground state is not as distorted from the hexagonal con­formation as previous X-ray data suggest: the principal parameters are NĈN = 124°.6; r(C—N) = 1.338Å; r (N—N) = 1.330Å; r (C—H) = 1.07 ± 0-02 Å.. On electronic excitation the N—N bond lengths are reduced by 0.11A and the separation of the carbon atoms increases by 0.10Å. It does not seem possible to understand the con­siderable change of geometry on excitation on the basis of simple Hiickel π-electron theory.

The electronic spectra of phenyl radicals

1965 ◽  
Vol 287 (1411) ◽  
pp. 457-470 ◽  
Keyword(s):  
Absorption Spectrum ◽  
Electronic Absorption Spectrum ◽  
Electronic Absorption ◽  
Ground State ◽  
Electronic Spectra ◽  
Flash Photolysis ◽  
Visible Region ◽  
Electronic Configuration ◽  
Vibrational Structure ◽  
Fundamental Frequencies

An electronic absorption spectrum, attributed to phenyl, has been observed in the visible region with origin at 18 908 cm -1 after flash photolysis of benzene and halogenobenzenes. Similar spectra of fluoro, chloro and bromo phenyl are observed after flash photolysis of disubstituted benzenes. The vibrational structure of the phenyl spectrum has been analysed in terms of two fundamental frequencies at 571 and 896 cm -1 which correspond to the e 2 g and a 1 g frequencies of the B 2 u state of benzene. The ground state of phenyl has a π 6 n electronic configuration and the observed transition is interpreted as 2 A 1 → 2 B 1 resulting from a π → n excitation.

Vibrational Structure of the High-Resolution UV Absorption Spectrum of Acetophenone in the Gas Phase

2021 ◽  
Vol 95 (10) ◽  
pp. 2090-2095
Author(s):  
L. A. Koroleva ◽  
K. S. Andriasov ◽  
A. V. Koroleva
Keyword(s):  
Absorption Spectrum ◽  
High Resolution ◽  
Gas Phase ◽  
Vibrational Structure ◽  
Uv Absorption ◽  
Uv Absorption Spectrum

THE ABSORPTION SPECTRUM OF CF2

1967 ◽  
Vol 45 (7) ◽  
pp. 2355-2374 ◽  
Author(s):  
C. Weldon Mathews
Keyword(s):  
Absorption Spectrum ◽  
Electronic State ◽  
Ground State ◽  
Band System ◽  
Electronic States ◽  
Vibrational Structure ◽  
Rotational Structure ◽  
Transition Moment ◽  
High Dispersion ◽  
Parallel Type

The absorption spectrum of CF2 in the 2 500 Å region has been photographed at high dispersion, and the rotational structure of a number of bands has been analyzed. The analysis of the well-resolved subbands establishes that these are perpendicular- rather than parallel-type bands, as previously assigned. Further analysis shows that the upper and lower electronic states are of 1B1 and 1A1symmetries respectively, corresponding to a transition moment that is perpendicular to the plane of the molecule. In the upper electronic state, r0(CF) = 1.32 Å and [Formula: see text], while in the ground state, r0(CF) = 1.300 Å and [Formula: see text]. An investigation of the vibrational structure of the band system has shown that the vibrational numbering in ν2′ must be increased by one unit from earlier assignments, thus placing the 000–000 band near 2 687 Å (37 220 cm−1). A search between 1 300 and 8 500 Å showed two new band systems near 1 350 and 1 500 Å which have been assigned tentatively to the CF2 molecule.

Vibrational Structure of a High-Resolution UV Absorption Spectrum of 2-Fluoroacryloyl Fluoride in the Gas Phase

2021 ◽  
Vol 76 (6) ◽  
pp. 370-379
Author(s):  
L. A. Koroleva ◽  
K. S. Andriasov ◽  
A. V. Koroleva
Keyword(s):  
Absorption Spectrum ◽  
High Resolution ◽  
Gas Phase ◽  
Vibrational Structure ◽  
Uv Absorption ◽  
Uv Absorption Spectrum

Vibrational structure of n–π* transition of the UV absorption spectrum of acryloyl fluoride in the gas phase

2014 ◽  
Vol 122 ◽  
pp. 609-615 ◽  
Author(s):  
Lidiya A. Koroleva ◽  
Vladimir I. Tyulin ◽  
Vladimir K. Matveev ◽  
Yuriy A. Pentin
Keyword(s):  
Absorption Spectrum ◽  
Gas Phase ◽  
Vibrational Structure ◽  
Uv Absorption ◽  
Uv Absorption Spectrum

The Near-ultraviolet Absorption Spectrum of Diimide in Liquid Ammonia and its Decomposition between −65 and −38 °C

1974 ◽  
Vol 52 (13) ◽  
pp. 2513-2515 ◽  
Author(s):  
R. A. Back ◽  
C. Willis
Keyword(s):  
Absorption Spectrum ◽  
Gas Phase ◽  
Room Temperature ◽  
Liquid Ammonia ◽  
Vibrational Structure ◽  
Ultraviolet Absorption ◽  
Ultraviolet Absorption Spectrum ◽  
First Order ◽  
Rapid Decomposition ◽  
Near Ultraviolet

The near-ultraviolet absorption spectrum of diimide in liquid ammonia at −50 °C is shifted about 500 Å to the red compared with the gas-phase spectrum, with λmax = 4000 Å. The spectrum is also broadened and the vibrational structure largely obscured. It is suggested that hydrogen bonding is responsible for these changes.Diimide is much more stable in liquid ammonia between −65 and −38 °C than in the gas phase at room temperature. A first-order decay is observed with Arrhenius parameters of A = 1.9 × 103 s−1 and E = 6.6 kcal/mol; this is always preceded by a more rapid, higher-order initial decay which may be related to the rapid decomposition observed during vaporization.

Vibrational Structure of a High-Resolution UV Absorption Spectrum of Benzaldehyde in the Gas Phase

2020 ◽  
Vol 94 (11) ◽  
pp. 2265-2271
Author(s):  
L. A. Koroleva ◽  
K. S. Andriasov ◽  
A. V. Koroleva
Keyword(s):  
Absorption Spectrum ◽  
High Resolution ◽  
Gas Phase ◽  
Vibrational Structure ◽  
Uv Absorption ◽  
Uv Absorption Spectrum

scholarly journals Role of active site conformational changes in photocycle activation of the AppA BLUF photoreceptor

2017 ◽  
Vol 114 (7) ◽  
pp. 1480-1485 ◽  
Author(s):  
Puja Goyal ◽  
Sharon Hammes-Schiffer
Keyword(s):  
Electron Transfer ◽  
Free Energy ◽  
Excited State ◽  
Charge Transfer ◽  
Conformational Changes ◽  
Ground State ◽  
Active Site ◽  
Locally Excited ◽  
Proton Relay ◽  
Locally Excited State

Blue light using flavin adenine dinucleotide (BLUF) proteins are essential for the light regulation of a variety of physiologically important processes and serve as a prototype for photoinduced proton-coupled electron transfer (PCET). Free-energy simulations elucidate the active site conformations in the AppA (activation of photopigment and puc expression) BLUF domain before and following photoexcitation. The free-energy profile for interconversion between conformations with either Trp104 or Met106 closer to the flavin, denoted Trpin/Metout and Trpout/Metin, reveals that both conformations are sampled on the ground state, with the former thermodynamically favorable by ∼3 kcal/mol. These results are consistent with the experimental observation of both conformations. To analyze the proton relay from Tyr21 to the flavin via Gln63, the free-energy profiles for Gln63 rotation were calculated on the ground state, the locally excited state of the flavin, and the charge-transfer state associated with electron transfer from Tyr21 to the flavin. For the Trpin/Metout conformation, the hydrogen-bonding pattern conducive to the proton relay is not thermodynamically favorable on the ground state but becomes more favorable, corresponding to approximately half of the configurations sampled, on the locally excited state. The calculated energy gaps between the locally excited and charge-transfer states suggest that electron transfer from Tyr21 to the flavin is more facile for configurations conducive to proton transfer. When the active site conformation is not conducive to PCET from Tyr21, Trp104 can directly compete with Tyr21 for electron transfer to the flavin through a nonproductive pathway, impeding the signaling efficiency.

Sign in / Sign up

Export Citation Format

Share Document