scholarly journals Vibrational coherence and quantum yield of retinal-chromophore-inspired molecular switches

2020 ◽  
Vol 221 ◽  
pp. 299-321 ◽  
Author(s):  
Moussa Gueye ◽  
Marco Paolino ◽  
Etienne Gindensperger ◽  
Stefan Haacke ◽  
Massimo Olivucci ◽  
...  
Keyword(s):  
Quantum Yield ◽  
Transient Absorption ◽  
Molecular Switches ◽  
Systematic Investigation ◽  
Vibrational Coherence ◽  
Retinal Chromophore ◽  
Molecular Framework

UV-Vis transient absorption (TA) spectroscopy is used to carry out a systematic investigation of the ultrafast CC double photoisomerization dynamics and quantum yield of each isomer of a set of six chromophores based on the same retinal-inspired, indanylidene pyrrolinium (IP) molecular framework.

scholarly journals Спектральное исследование фотодинамических процессов в системе C-=SUB=-60-=/SUB=--(н-метилпирролидон)-кислород

2021 ◽  
Vol 129 (12) ◽  
pp. 1493
Author(s):  
И.М. Кисляков ◽  
И.М. Белоусова ◽  
В.М. Киселев ◽  
И.В. Багров ◽  
А.М. Стародубцев ◽  
...  
Keyword(s):  
Quantum Yield ◽  
Singlet Oxygen ◽  
Transient Absorption ◽  
Rapid Quenching ◽  
Quenching Rate ◽  
Broadband Absorption ◽  
Laser Pumping ◽  
Time Dependencies ◽  
Quenching Rate Constant

The processes of photoexcitation and energy transfer in an air-saturated solution of fullerene C60 in n-methylpyrrolidone are studied. With femtosecond laser pumping at a wavelength л(p) = 520 nm, transient absorption spectra were obtained in the range 470-750 nm. Broadband absorption is observed at л > 650 nm as a result of aggregation of fullerene molecules, characterized by a short decay time of the picosecond scale. The analysis of the time dependencies indicates the presence of several processes. Within the proposed interpretation, we state a remarkable reduction in the time of singlet-triplet intersystem crossing with an increase of nanocluster size while the rapid quenching of the singlet state varies only slightly. The quantum yield of the triplet state can therefore increase, reaching 0.14. The phosphorescence spectra of singlet oxygen with a maximum at л = 1276 nm were measured with LED excitation at various wavelengths in the range 370-625 nm. The lifetime and quenching rate constant of singlet oxygen in n-methylpyrrolidone are determined. The combined quantum yield of triplet fullerene and singlet oxygen in n-methylpyrrolidone is estimated as 0.74. The efficiency spectra of the singlet oxygen photosensibilization in the C60-(n-methylpyrrolidone)-oxygen system are obtained, indicating the increasing role of large nanoclusters in this process during aging of the solution.

scholarly journals Mechanistic Investigations of an α-Aminoarylation Photoredox Reaction

2021 ◽  
Author(s):  
Bernard Stevenson ◽  
Ethan Spielvogel ◽  
Emily Loiaconi ◽  
Victor M. Wambua ◽  
Roman Nakhamiyayev ◽  
...  
Keyword(s):  
Quantum Yield ◽  
Absorption Spectroscopy ◽  
Rate Constant ◽  
Kinetic Modeling ◽  
Rate Constants ◽  
Transient Absorption ◽  
Coupling Reaction ◽  
Time Dependent ◽  
Transient Absorption Spectroscopy ◽  
Mechanistic Investigations

We present time-dependent percent and quantum yield measurements of a photoredox-catalyzed coupling reaction between 1,4-dicyanobenzene and N-phenylpyrrolidine. We also use transient absorption spectroscopy to examine the kinetics within the reaction and use kinetic modeling to extract rate constants and predict how changes in rate constant will impact the quantum yield.

scholarly journals The structural biology of voltage-gated calcium channel function and regulation

2006 ◽  
Vol 34 (5) ◽  
pp. 887-893 ◽  
Author(s):  
F. Van Petegem ◽  
D.L. Minor
Keyword(s):  
Neurotransmitter Release ◽  
Action Potentials ◽  
Molecular Switches ◽  
Voltage Gated ◽  
Calcium Dependent ◽  
Voltage Gated Calcium Channels ◽  
Dependent Inactivation ◽  
Voltage Dependent ◽  
Soluble Calcium ◽  
Molecular Framework

Voltage-gated calcium channels (CaVs) are large (∼0.5 MDa), multisubunit, macromolecular machines that control calcium entry into cells in response to membrane potential changes. These molecular switches play pivotal roles in cardiac action potentials, neurotransmitter release, muscle contraction, calcium-dependent gene transcription and synaptic transmission. CaVs possess self-regulatory mechanisms that permit them to change their behaviour in response to activity, including voltage-dependent inactivation, calcium-dependent inactivation and calcium-dependent facilitation. These processes arise from the concerted action of different channel domains with CaV β-subunits and the soluble calcium sensor calmodulin. Until recently, nothing was known about the CaV structure at high resolution. Recent crystallographic work has revealed the first glimpses at the CaV molecular framework and set a new direction towards a detailed mechanistic understanding of CaV function.

Impact of Vibrational Coherence on the Quantum Yield at a Conical Intersection

2016 ◽  
Vol 7 (17) ◽  
pp. 3491-3496 ◽  
Author(s):  
Hong-Guang Duan ◽  
R. J. Dwayne Miller ◽  
Michael Thorwart
Keyword(s):  
Quantum Yield ◽  
Conical Intersection ◽  
Vibrational Coherence

scholarly journals Direct observation of light-driven, concerted electron–proton transfer

2016 ◽  
Vol 113 (40) ◽  
pp. 11106-11109 ◽  
Author(s):  
Christopher J. Gagliardi ◽  
Li Wang ◽  
Prateek Dongare ◽  
M. Kyle Brennaman ◽  
John M. Papanikolas ◽  
...  
Keyword(s):  
Proton Transfer ◽  
Transient Absorption ◽  
Observation Time ◽  
Low Energy ◽  
Vibrational Coherence ◽  
Visible Spectra ◽  
Transient Spectra ◽  
Uv Visible ◽  
Electron Proton Transfer ◽  
Absorption Measurements

The phenols 4-methylphenol, 4-methoxyphenol, and N-acetyl-tyrosine form hydrogen-bonded adducts with N-methyl-4, 4′-bipyridinium cation (MQ+) in aqueous solution as evidenced by the appearance of low-energy, low-absorptivity features in UV-visible spectra. They are assigned to the known examples of optically induced, concerted electron–proton transfer, photoEPT. The results of ultrafast transient absorption measurements on the assembly MeOPhO-H---MQ+ are consistent with concerted EPT by the instantaneous appearance of spectral features for MeOPhO·---H-MQ+ in the transient spectra at the first observation time of 0.1 ps. The transient decays to MeOPhO-H---MQ+ in 2.5 ps, accompanied by the appearance of oscillations in the decay traces with a period of ∼1 ps, consistent with a vibrational coherence and relaxation from a higher υ(N-H) vibrational level or levels on the timescale for back EPT.

Optomechanical Control of Quantum Yield in Trans -Cis Ultrafast Photoisomerization of a Retinal Chromophore Model

2017 ◽  
Vol 56 (14) ◽  
pp. 3842-3846 ◽  
Author(s):  
Alessio Valentini ◽  
Daniel Rivero ◽  
Felipe Zapata ◽  
Cristina García-Iriepa ◽  
Marco Marazzi ◽  
...  
Keyword(s):  
Quantum Yield ◽  
Retinal Chromophore ◽  
In Trans

scholarly journals Approaching the Spin-Statistical Limit in Visible-to-UV Photon Upconversion

2021 ◽  
Author(s):  
Axel Olesund ◽  
Jessica Johnsson ◽  
Fredrik Edhborg ◽  
Shima Ghasemi ◽  
Kasper Moth-Poulsen ◽  
...  
Keyword(s):  
Quantum Yield ◽  
Transient Absorption ◽  
High Energy ◽  
Delayed Fluorescence ◽  
Photochemical Reactions ◽  
Quantum Yields ◽  
Great Promise ◽  
Time Resolved ◽  
Statistical Limit ◽  
Triplet Triplet Annihilation

Triplet-triplet annihilation photon upconversion (TTA-UC) is a process in which triplet excitons combine to form emissive singlets, and holds great promise to improve the spectral match in solar energy and biological applications. While high TTA-UC quantum yields has been reported for e.g., red-to-green TTA-UC systems there are only a few examples of visible-to-UV transformations in which the quantum yield reaches 10%. In this study we investigate the performance of six annihilators when paired with the sensitizer 2,3,5,6-tetra(9H-carbazol-9-yl)benzonitrile (4CzBN), a purely organic compound that exhibits thermally activated delayed fluorescence (TADF). We report a record-setting TTA-UC quantum yield of 16.8% (out of a 50% maximum) for 1,4-bis((triisopropylsilyl)ethynyl)naphthalene (TIPS-Naph), demonstrating the first example of a visible-to-UV TTA-UC system approaching the classical spin-statistical limit of 20%. Three other annihilators, of which 2,5-diphenylfuran (PPF) has never been used for TTA-UC previously, also showed impressive performances with TTA-UC quantum yields above 12%. In addition, a new method to determine the rate constant of triplet-triplet annihilation is proposed in which only time-resolved emission measurements are needed, circumventing the need for more challenging transient absorption measurements. The results reported herein represent an important step towards highly efficient visible-to-UV TTA-UC systems which hold great potential for driving high-energy photochemical reactions.

scholarly journals Quantifying Triplet State Formation in Zinc Dipyrrin Complexes

2019 ◽  
Author(s):  
Norah Z. Alqahtani ◽  
Toni G. Blevins ◽  
Catherine McCusker
Keyword(s):  
Quantum Yield ◽  
Triplet State ◽  
State Formation ◽  
Transient Absorption ◽  
Photophysical Properties ◽  
Solvent Polarity ◽  
Transient Absorption Spectroscopy ◽  
Heavy Atoms ◽  
Earth Abundant ◽  
Photocatalytic Reactions

Photocatalysis is a promising method to harness solar energy and use it to form fuels and other high value chemicals, but most sensitizers used in photocatalytic reactions are complexes of rare and expensive metals such as ruthenium and iridium. Zinc dipyrromethene complexes have potential to be a more earth-abundant alternative, but their photophysical properties are largely unexplored. In this study, triplet state formation was quantified in two zinc dipyrromethene complexes, with a and without heavy atoms, by transient absorption spectroscopy. Without heavy atoms the triplet quantum yield was 16% in toluene and 27% in THF. With the addition of heavy I atoms the triplet quantum yield is increased to 62-63% and is insensitive to solvent polarity. These triplet yields meet or exceed those of successful organic photosensitizers, illustrating the potential for zinc dipyrromethene complexes as photosensitizers

scholarly journals Femtosecond Time Resolved Infrared Spectroscopy of the Ethylenic Stretch Vibration During the all-Trans to 13-Cis Isomerization of Bacteriorhodopsin

1999 ◽  
Vol 19 (1-4) ◽  
pp. 173-178 ◽  
Author(s):  
Reiner Dziewior ◽  
Karsten Romey ◽  
Rolf Diller
Keyword(s):  
Absorption Band ◽  
Vibrational Relaxation ◽  
Room Temperature ◽  
Transient Absorption ◽  
Difference Spectrum ◽  
Low Energy ◽  
Time Resolved ◽  
Stretch Vibration ◽  
Retinal Chromophore ◽  
Time Resolved Infrared Spectroscopy

We report on room temperature infrared transient absorption experiments on Bacteriorhodopsin concerning the early picosecond dynamics of the all trans to 13-cis isomerization of the retinal chromophore. The absorption band of the all-trans chromophore ethylenic stretch vibration bleaches concomitantly to photoexcitation whereas new absorption strength is created redshifted within less than 1 ps. the initial bleach recovers partly according to the non unity quantum yield of the photoisomerization within 2 ps. With a time constant of 3ps the low energy absorption band is downshifled 5–10 cm-1. Thus, vibrational relaxation and cooling processes appear to have ended within a few ps and on the time scale of 20 ps a stationary BR-K difference spectrum is obtained.

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