scholarly journals Don’t help them to bury the light. The interplay between intersystem crossing and hydrogen transfer in photoexcited curcumin revealed by state-hopping dynamics.

2021 ◽  
Author(s):  
Raul Losantos ◽  
Andreea Pasc ◽  
Antonio Monari
Keyword(s):  
Hydrogen Transfer ◽  
Intersystem Crossing

Don’t help them to bury the light. The interplay between intersystem crossing and hydrogen transfer in photoexcited curcumin revealed by state-hopping dynamics

2021 ◽  
Author(s):  
Raúl Losantos ◽  
Andreea Pasc ◽  
Antonio Monari
Keyword(s):  
Natural Compound ◽  
Hydrogen Transfer ◽  
Curcuma Longa ◽  
Intersystem Crossing ◽  
Intense Absorption

Curcumin is a natural compound extracted from turmeric (curcuma longa), which has shown remarkable antiinflammatory, antibacterial, and possibly anticancert properties. The intense absorption in the visible domain, and the possibility...

Solvent-Dependent Excited-State Hydrogen Transfer and Intersystem Crossing in 2-(2′-Hydroxyphenyl)-Benzothiazole

2014 ◽  
Vol 119 (6) ◽  
pp. 2596-2603 ◽  
Author(s):  
Shawkat M. Aly ◽  
Anwar Usman ◽  
Maytham AlZayer ◽  
Ghada A. Hamdi ◽  
Erkki Alarousu ◽  
...  
Keyword(s):  
Excited State ◽  
Hydrogen Transfer ◽  
Intersystem Crossing

Excited state hydrogen transfer dynamics in phenol–(NH3)2 studied by picosecond UV-near IR-UV time-resolved spectroscopy

2020 ◽  
Vol 22 (10) ◽  
pp. 5740-5748
Author(s):  
Shun-ichi Ishiuchi ◽  
Junko Kamizori ◽  
Norihiro Tsuji ◽  
Makoto Sakai ◽  
Mitsuhiko Miyazaki ◽  
...  
Keyword(s):  
Excited State ◽  
Hydrogen Transfer ◽  
Transfer Reaction ◽  
Bound State ◽  
Intersystem Crossing ◽  
Time Resolved ◽  
Time Resolved Spectroscopy ◽  
Hydrogen Transfer Reaction ◽  
Near Ir

Intersystem crossing from 1πσ* to 3πσ* states traps excited state hydrogen transfer reaction in a bound state formed by 3ππ* and 3πσ* states.

scholarly journals Probing Competing Relaxation Pathways in Malonaldehyde with Transient X-Ray Absorption Spectroscopy

2020 ◽  
Author(s):  
Nanna Holmgaard List ◽  
Adrian L. Dempwolff ◽  
Andreas Dreuw ◽  
Patrick Norman ◽  
Todd J. Martínez
Keyword(s):  
Excited State ◽  
Absorption Spectroscopy ◽  
Hydrogen Transfer ◽  
Intersystem Crossing ◽  
Light Sources ◽  
X Ray ◽  
Valence States ◽  
Specific Mapping ◽  
Intramolecular Hydrogen ◽  
X Ray Absorption

<p>Excited-state intramolecular hydrogen transfer (ESIHT) is a fundamental reaction relevant to chemistry and biology. Malonaldehyde is the simplest example of ESIHT, yet only little is known experimentally about its excited-state dynamics. Several competing relaxation pathways have been proposed, including internal conversion mediated by ESIHT and C=C torsional motion as well as intersystem crossing. We perform an in silico transient X-ray absorption spectroscopy (TRXAS) experiment at the oxygen K-edge to investigate its potential to monitor the proposed ultrafast decay pathways in malonaldehyde upon photoexcitation to its bright S2(pp*) state. We employ both restricted active space perturbation theory and algebraic diagrammatic construction for the polarization propagator along interpolated reaction coordinates as well as representative trajectories from ab initio multiple spawning simulations to compute the TRXAS signals from the lowest valence states. Our study suggests that oxygen K-edge TRXAS can distinctly fingerprint the passage through the H-transfer intersection and the concomitant population transfer to the S1(np*) state. Potential intersystem crossing to T1(pp*) is detectable from reappearance of the double pre-edge signature and reversed intensities. Moreover, the torsional deactivation pathway induces transient charge redistribution from the enol side towards the central C-atom and manifests itself as substantial shifts of the pre-edge features. Given the continuous advances in X-ray light sources, our study proposes an experimental route to disentangle ultrafast excited-state decay channels in this prototypical ESIHT system and provides a pathway-specific mapping of the TRXAS signal to facilitate the interpretation of future experiments.</p>

scholarly journals Probing Competing Relaxation Pathways in Malonaldehyde with Transient X-Ray Absorption Spectroscopy

2020 ◽  
Author(s):  
Nanna Holmgaard List ◽  
Adrian L. Dempwolff ◽  
Andreas Dreuw ◽  
Patrick Norman ◽  
Todd J. Martínez
Keyword(s):  
Excited State ◽  
Absorption Spectroscopy ◽  
Hydrogen Transfer ◽  
Intersystem Crossing ◽  
Light Sources ◽  
X Ray ◽  
Valence States ◽  
Specific Mapping ◽  
Intramolecular Hydrogen ◽  
X Ray Absorption

<p>Excited-state intramolecular hydrogen transfer (ESIHT) is a fundamental reaction relevant to chemistry and biology. Malonaldehyde is the simplest example of ESIHT, yet only little is known experimentally about its excited-state dynamics. Several competing relaxation pathways have been proposed, including internal conversion mediated by ESIHT and C=C torsional motion as well as intersystem crossing. We perform an in silico transient X-ray absorption spectroscopy (TRXAS) experiment at the oxygen K-edge to investigate its potential to monitor the proposed ultrafast decay pathways in malonaldehyde upon photoexcitation to its bright S2(pp*) state. We employ both restricted active space perturbation theory and algebraic diagrammatic construction for the polarization propagator along interpolated reaction coordinates as well as representative trajectories from ab initio multiple spawning simulations to compute the TRXAS signals from the lowest valence states. Our study suggests that oxygen K-edge TRXAS can distinctly fingerprint the passage through the H-transfer intersection and the concomitant population transfer to the S1(np*) state. Potential intersystem crossing to T1(pp*) is detectable from reappearance of the double pre-edge signature and reversed intensities. Moreover, the torsional deactivation pathway induces transient charge redistribution from the enol side towards the central C-atom and manifests itself as substantial shifts of the pre-edge features. Given the continuous advances in X-ray light sources, our study proposes an experimental route to disentangle ultrafast excited-state decay channels in this prototypical ESIHT system and provides a pathway-specific mapping of the TRXAS signal to facilitate the interpretation of future experiments.</p>

Effect of Niacin on Mitochondria of Allium Cepa Root Cells

1967 ◽  
Vol 25 ◽  
pp. 78-79
Author(s):  
M. Arif Hayat
Keyword(s):  
Nicotinamide Adenine Dinucleotide ◽  
Hydrogen Transfer ◽  
Nicotinamide Adenine Dinucleotide Phosphate ◽  
Nicotinamide Adenine ◽  
Root Tips ◽  
Root Cells ◽  
Transfer Processes ◽  
Standard Procedures ◽  
A Cell ◽  
Critical Interest

Although it is recognized that niacin (pyridine-3-carboxylic acid), incorporated as the amide in nicotinamide adenine dinucleotide (NAD) or in nicotinamide adenine dinucleotide phosphate (NADP), is a cofactor in hydrogen transfer in numerous enzyme reactions in all organisms studied, virtually no information is available on the effect of this vitamin on a cell at the submicroscopic level. Since mitochondria act as sites for many hydrogen transfer processes, the possible response of mitochondria to niacin treatment is, therefore, of critical interest.Onion bulbs were placed on vials filled with double distilled water in the dark at 25°C. After two days the bulbs and newly developed root system were transferred to vials containing 0.1% niacin. Root tips were collected at ¼, ½, 1, 2, 4, and 8 hr. intervals after treatment. The tissues were fixed in glutaraldehyde-OsO4 as well as in 2% KMnO4 according to standard procedures. In both cases, the tissues were dehydrated in an acetone series and embedded in Reynolds' lead citrate for 3-10 minutes.

Cobalt/Lewis Acid Catalysis for Hydrocarbofunctionalization of Alkynes via Cooperative C–H Activation

2020 ◽  
Author(s):  
Chang-Sheng Wang ◽  
Sabrina Monaco ◽  
Anh Ngoc Thai ◽  
Md. Shafiqur Rahman ◽  
Chen Wang ◽  
...  
Keyword(s):  
Catalytic System ◽  
Lewis Acid ◽  
Hydrogen Transfer ◽  
Acid Catalysis ◽  
Rate Limiting Step ◽  
Site Selectivity ◽  
Set Up ◽  
Site Selective ◽  
First Time ◽  
Rate Limiting

A catalytic system comprised of a cobalt-diphosphine complex and a Lewis acid (LA) such as AlMe3 has been found to promote hydrocarbofunctionalization reactions of alkynes with Lewis basic and electron-deficient substrates such as formamides, pyridones, pyridines, and azole derivatives through site-selective C-H activation. Compared with known Ni/LA catalytic system for analogous transformations, the present catalytic system not only feature convenient set up using inexpensive and bench-stable precatalyst and ligand such as Co(acac)3 and 1,3-bis(diphenylphosphino)propane (dppp), but also display distinct site-selectivity toward C-H activation of pyridone and pyridine derivatives. In particular, a completely C4-selective alkenylation of pyridine has been achieved for the first time. Mechanistic stidies including DFT calculations on the Co/Al-catalyzed addition of formamide to alkyne have suggested that the reaction involves cleavage of the carbamoyl C-H bond as the rate-limiting step, which proceeds through a ligand-to-ligand hydrogen transfer (LLHT) mechanism leading to an alkyl(carbamoyl)cobalt intermediate.

Spin-Forbidden Excitation Enables Infrared Photoredox Catalysis

2020 ◽  
Author(s):  
Tomislav Rovis ◽  
Benjamin D. Ravetz ◽  
Nicholas E. S. Tay ◽  
Candice Joe ◽  
Melda Sezen-Edmonds ◽  
...  
Keyword(s):  
Excited State ◽  
Ground State ◽  
Intersystem Crossing ◽  
Photoredox Catalysis ◽  
Infrared Irradiation ◽  
Triplet Excitation ◽  
New Family ◽  
Ir Light

We describe a new family of catalysts that undergo direct ground state singlet to excited state triplet excitation with IR light, leading to photoredox catalysis without the energy waste associated with intersystem crossing. The finding allows a mole scale reaction in batch using infrared irradiation.

Nanometer Scale Spectroscopic Visualization of Catalytic Sites During a Hydrogenation Reaction on a Pd/Au Bimetallic Catalyst

2020 ◽  
Author(s):  
hao yin ◽  
Liqing Zheng ◽  
Wei Fang ◽  
Yin-Hung Lai ◽  
Nikolaus Porenta ◽  
...  
Keyword(s):  
Catalytic Hydrogenation ◽  
Density Functional ◽  
Hydrogen Transfer ◽  
Bimetallic Catalyst ◽  
Local Environment ◽  
Hydrogenation Reaction ◽  
Boundary Density ◽  
Catalytic Sites ◽  
Powerful Analytical Tool ◽  
Tip Enhanced Raman Spectroscopy

<p>Understanding the mechanism of catalytic hydrogenation at the local environment requires chemical and topographic information involving catalytic sites, active hydrogen species and their spatial distribution. Here, tip-enhanced Raman spectroscopy (TERS) was employed to study the catalytic hydrogenation of chloro-nitrobenzenethiol on a well-defined Pd(sub-monolayer)/Au(111) bimetallic catalyst (<i>p</i><sub>H2</sub>=1.5 bar, 298 K), where the surface topography and chemical fingerprint information were simultaneously mapped with nanoscale resolution (≈10 nm). TERS imaging of the surface after catalytic hydrogenation confirms that the reaction occurs beyond the location of Pd sites. The results demonstrate that hydrogen spillover accelerates hydrogenation at the Au sites within 20 nm from the bimetallic Pd/Au boundary. Density functional theory was used to elucidate the thermodynamics of interfacial hydrogen transfer. We demonstrate that TERS as a powerful analytical tool provides a unique approach to spatially investigate the local structure-reactivity relationship in catalysis.</p>

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