The photodissociation of N,N-dimethylnitrosamine at 355 nm: The effect of excited-state conformational changes on product vector correlations

2017 ◽  
Vol 147 (1) ◽  
pp. 013925 ◽  
Author(s):  
Masroor Hossain ◽  
Aidan J. Klobuchar ◽  
Jeffrey A. Bartz
Keyword(s):  
Excited State ◽  
Conformational Changes ◽  
Vector Correlations ◽  
Product Vector

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.

Intramolecular Charge Transfer Assisted by Conformational Changes in the Excited State of Fluorene-dibenzothiophene-S,S-dioxide Co-oligomers

2006 ◽  
Vol 110 (39) ◽  
pp. 19329-19339 ◽  
Author(s):  
Fernando B. Dias ◽  
Sam Pollock ◽  
Gordon Hedley ◽  
Lars-Olof Pålsson ◽  
Andy Monkman ◽  
...  
Keyword(s):  
Excited State ◽  
Charge Transfer ◽  
Conformational Changes ◽  
Intramolecular Charge Transfer

Development of solid-state emissive o-carboranes and theoretical investigation of the mechanism of the aggregation-induced emission behaviors of organoboron “element-blocks”

2017 ◽  
Vol 196 ◽  
pp. 31-42 ◽  
Author(s):  
Kazuo Tanaka ◽  
Kenta Nishino ◽  
Shunichiro Ito ◽  
Honami Yamane ◽  
Kazumasa Suenaga ◽  
...  
Keyword(s):  
Excited State ◽  
Conformational Changes ◽  
Functional Group ◽  
Theoretical Calculations ◽  
Luminescent Properties ◽  
Ring Structure ◽  
Aggregation Induced Emission ◽  
Intramolecular Mobility ◽  
Fused Ring ◽  
Potential Strategy

This paper presents the aggregation-induced emission (AIE) properties of o-carborane derivatives and proposes a potential strategy for constructing AIE-active organoboron complexes via the enhancement of freedom of intramolecular mobility. Initially, the optical properties of o-carborane derivatives with or without the fused ring structure at the C–C bond in o-carborane in which elongation should be induced by photo-excitation according to theoretical calculations were compared. Accordingly, it was shown that large mobility at the C–C bond in o-carborane should be responsible for the annihilation of emission in solution, leading to the AIE property. From this result, it was presumed that by enhancing the freedom of intramolecular mobility in conventional luminescent organoboron complexes, the deactivation of the excited state in solution and emission recovery in the aggregate can be induced. Based on this idea, we have performed several studies and introduce two representative results. Firstly, the decrease in luminescent properties of boron dipyrromethene (BODIPY) in solution by introducing a movable functional group is explained. Next, the AIE behaviors of boron ketoiminates and the potential mechanism concerning conformational changes for the deactivation of the excited state in the solution state are illustrated. It is proposed that enhancement of the freedom of mobility in the excited state of luminescent organoboron complexes could be a potential strategy for realizing AIE behaviors.

scholarly journals Disentanglement of excited-state dynamics with implications for FRET measurements: two-dimensional electronic spectroscopy of a BODIPY-functionalized cavitand

2018 ◽  
Vol 9 (15) ◽  
pp. 3694-3703 ◽  
Author(s):  
John P. Otto ◽  
Lili Wang ◽  
Igor Pochorovski ◽  
Samuel M. Blau ◽  
Alán Aspuru-Guzik ◽  
...  
Keyword(s):  
Energy Transfer ◽  
Excited State ◽  
Conformational Changes ◽  
Electronic Spectroscopy ◽  
Two Dimensional ◽  
Excited State Dynamics ◽  
Competing Dynamics

Two-dimensional electronic spectroscopy of energy transfer and competing dynamics highlights how conformational changes create issues with lifetime-based FRET measurements.

Deactivation of the S,-State of w-Substituted 4-Dimethylamino-trans-Styrenes in Alkane Solutions

1991 ◽  
Vol 46 (12) ◽  
pp. 1043-1048
Author(s):  
A. Kawski ◽  
I. Gryczyński ◽  
K. Nowaczyk ◽  
P. Bojarski ◽  
J. Lichacz
Keyword(s):  
Excited State ◽  
Double Bond ◽  
Fluorescence Quenching ◽  
Conformational Changes ◽  
Linear Dependence ◽  
Fluorescence Anisotropy ◽  
Intersystem Crossing ◽  
Strong Fluorescence ◽  
Fluorescence Depolarization ◽  
High Fluorescence

Abstract Deactivation of three co-substituted acceptors in 4-dimethylamino-trans-styrenes (P(S)Ph2 (la), P(0)Ph2 (2a) and SO2CH3 (3a)), dissolved in «-paraffins (from n = 5 to n = 16) at 293 K, was investigated. Trans-cis isomerization and intersystem crossing are the main processes responsible for radiationless deactivation of the S1 excited state. High fluorescence anisotropy, r, observed in low-viscous «-paraffins, is due to strong fluorescence quenching resulting in the considerable shortening of the lifetime τ of these molecules. The fluorescence depolarization which occurs when lowering the viscosity, η, of the solution is caused by Brownian rotations and conformational changes due to fast adiabatic twisting of the planar trans-S1 form around the double bond, leading to the formation of the perp.-S1 structure with perpendicularly oriented parts of the molecule, and to the concomitant change in the transition moment direction. Linear dependence of τ2{r0/r - 1) on η - τ in the whole viscosity range was only observed for molecule 3a

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.

Structural implications on the excitation dynamics of fluorescent 3H-indolium cations

2017 ◽  
Vol 19 (19) ◽  
pp. 11904-11913 ◽  
Author(s):  
Ek Raj Thapaliya ◽  
Jaume Garcia-Amorós ◽  
Santi Nonell ◽  
Burjor Captain ◽  
Françisco M. Raymo
Keyword(s):  
Excited State ◽  
Conformational Changes ◽  
State Control ◽  
Excitation Dynamics

Conformational changes in the excited state control the excitation dynamics of fluorescent 3H-indolium cations.

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