scholarly journals Electron transfer dynamics and excited state branching in a charge-transfer platinum(ii) donor–bridge-acceptor assembly

2014 ◽  
Vol 43 (47) ◽  
pp. 17677-17693 ◽  
Author(s):  
Paul A. Scattergood ◽  
Milan Delor ◽  
Igor V. Sazanovich ◽  
Oleg V. Bouganov ◽  
Sergei A. Tikhomirov ◽  
...  
Keyword(s):  
Electron Transfer ◽  
Excited State ◽  
Charge Transfer ◽  
A Charge

scholarly journals Sensitization of ultra-long-range excited-state electron transfer by energy transfer in a polymerized film

2012 ◽  
Vol 109 (38) ◽  
pp. 15132-15135 ◽  
Author(s):  
Akitaka Ito ◽  
David J. Stewart ◽  
Zhen Fang ◽  
M. Kyle Brennaman ◽  
Thomas J. Meyer
Keyword(s):  
Electron Transfer ◽  
Energy Transfer ◽  
Excited State ◽  
Charge Transfer ◽  
Long Range ◽  
Methyl Viologen ◽  
Polymer Network ◽  
Triplet Energy ◽  
Ligand Charge Transfer ◽  
Triplet Energy Transfer

Distance-dependent energy transfer occurs from the Metal-to-Ligand Charge Transfer (MLCT) excited state to an anthracene-acrylate derivative (Acr-An) incorporated into the polymer network of a semirigid poly(ethyleneglycol)dimethacrylate monolith. Following excitation, to Acr-An triplet energy transfer occurs followed by long-range, Acr-3An—Acr-An → Acr-An—Acr-3An, energy migration. With methyl viologen dication (MV2+) added as a trap, Acr-3An + MV2+ → Acr-An+ + MV+ electron transfer results in sensitized electron transfer quenching over a distance of approximately 90 Å.

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.

scholarly journals Structure-Photochemical Function Relationships in Nitrogen-Containing Heterocyclic Aromatic Photobases Derived from Quinoline

2019 ◽  
Author(s):  
Sophya Alamudun ◽  
Kyle Tanovitz ◽  
April Fajardo ◽  
Kaitlind Johnson ◽  
Andy Pham ◽  
...  
Keyword(s):  
Excited State ◽  
Charge Transfer ◽  
Excitation Energy ◽  
Systematic Study ◽  
Experimental Studies ◽  
Substituent Effects ◽  
Vertical Excitation ◽  
Vertical Excitation Energy ◽  
Heterocyclic Aromatics ◽  
A Charge

<p>Photobases are compounds which become strong bases after electronic excitaton into a charge-transfer excited state. Recent experimental studies have highlighted the photobasicity of the 5-R quinoline compounds, demonstrating a strong substituent dependence to the pK<sub>a</sub><sup>*</sup>. Here we describe our systematic study of how the photobasicity of four families of nitrogen-containing heterocyclic aromatics are tuned through substituents. We show that substituent position and identity both significantly impact the pK<sub>a</sub><sup>*</sup>. We demonstrate that the substituent effects are additive and identify many disubstituted compounds with substantially greater photobasicity than the most photobasic 5-R quinoline compound identified previously. We show that the addition of a second fused benzene ring to quinoline, along with two electron-donating substituents, lowers the vertical excitation energy into the visible while still maintaining a pK<sub>a</sub><sup>*</sup> > 14. Overall, the structure-function relationships developed in this study provide new insights to guide the development of new photocatalysts that employ photobasicity. </p>

Luminescence and reactivity of a charge-transfer excited iron complex with nanosecond lifetime

Science ◽  
2018 ◽  
Vol 363 (6424) ◽  
pp. 249-253 ◽  
Author(s):  
Kasper Skov Kjær ◽  
Nidhi Kaul ◽  
Om Prakash ◽  
Pavel Chábera ◽  
Nils W. Rosemann ◽  
...  
Keyword(s):  
Electron Transfer ◽  
Charge Transfer ◽  
Room Temperature ◽  
Iron Complex ◽  
Transfer Reactions ◽  
Carbene Ligands ◽  
Doublet Ground State ◽  
A Charge ◽  
Bimolecular Quenching ◽  
Metal Charge Transfer

Iron’s abundance and rich coordination chemistry are potentially appealing features for photochemical applications. However, the photoexcitable charge-transfer states of most iron complexes are limited by picosecond or subpicosecond deactivation through low-lying metal-centered states, resulting in inefficient electron-transfer reactivity and complete lack of photoluminescence. In this study, we show that octahedral coordination of iron(III) by two mono-anionic facialtris-carbene ligands can markedly suppress such deactivation. The resulting complex [Fe(phtmeimb)2]+, where phtmeimb is {phenyl[tris(3-methylimidazol-1-ylidene)]borate}−, exhibits strong, visible, room temperature photoluminescence with a 2.0-nanosecond lifetime and 2% quantum yield via spin-allowed transition from a doublet ligand-to-metal charge-transfer (2LMCT) state to the doublet ground state. Reductive and oxidative electron-transfer reactions were observed for the2LMCT state of [Fe(phtmeimb)2]+in bimolecular quenching studies with methylviologen and diphenylamine.

Wave-Function Symmetry Control of Electron-Transfer Pathways within a Charge-Transfer Chromophore

2020 ◽  
Vol 11 (19) ◽  
pp. 8399-8405
Author(s):  
Bruno M. Aramburu-Trošelj ◽  
Ivana Ramírez-Wierzbicki ◽  
Franco Scarcasale ◽  
Paola S. Oviedo ◽  
Luis M. Baraldo ◽  
...  
Keyword(s):  
Electron Transfer ◽  
Wave Function ◽  
Charge Transfer ◽  
Electron Transfer Pathways ◽  
A Charge
Sign in / Sign up

Export Citation Format

Share Document