The photochemical reaction of tris(ethylenediamine)cobalt(III) ion with ferrocyanide

1981 ◽  
Vol 59 (4) ◽  
pp. 647-651 ◽  
Author(s):  
Cooper H. Langford ◽  
Roger L. P. Sasseville
Keyword(s):  
Electron Transfer ◽  
Excited State ◽  
Excited States ◽  
Photochemical Reaction ◽  
Ion Pairs ◽  
Ligand Field ◽  
Excited State Lifetime ◽  
Photochemical Formation ◽  
Reaction Proceeds ◽  
Reactive Excited State

The photochemical formation of [Cl(en)2Co—N≡C—Fe(CN)5]2− from Co(en)33+ and Fe(CN)64− is explored. Earlier evidence established that the reaction proceeds via electron transfer. Ligand field Co(III) excited states are clearly indicated to be effective. There is evidence that free Fe(CN)64− can scavenge these excited states or their successors arising in ion pairs with Fe(CN)64−. This suggests that the reactive excited state lifetime is at least comparable to the rate of diffusional encounters. However, racemization does not accompany reaction if (+)589Co(en)33+ is the reactant. Wavelength studies indicate approximate wavelength independence as far as 647.1 nm. These results are in contrast with the behaviour of photosubstitution yields for Co(III) amines.

scholarly journals Assessing the Accuracy of Simplified Coupled Cluster Methods for Electronic Excited States in F0 Actinide Compounds

2019 ◽  
Author(s):  
Artur Nowak ◽  
Paweł Tecmer ◽  
Katharina Boguslawski
Keyword(s):  
Electron Transfer ◽  
Excited State ◽  
Excited States ◽  
Coupled Cluster ◽  
Electronic Excitations ◽  
Electronic Excited States ◽  
Benchmark Study ◽  
Double Electron ◽  
Different Types ◽  
Cluster Methods

<p>We present a benchmark study of the performance of various recently presented EOM-pCCD-based methods to model ground and excited state properties of a set of f0 actinide species that feature different types of electronic excitations, like local excitations or charge transfer. Our data suggests that the recently developed EOM-pCCD-LCCSD method outperforms conventional approaches like EOM-CCSD reducing the standard error by a factor of 2 (to 0.25 eV). Thus, EOM-pCCD-LCCSD can be considered as an alternative to model excited states in challenging systems, especially those who feature a double electron transfer for which EOM-CCSD typically fails.</p>

scholarly journals Two-electron transfer stabilized by excited-state aromatization

2019 ◽  
Vol 10 (1) ◽  
Author(s):  
Jinseok Kim ◽  
Juwon Oh ◽  
Seongchul Park ◽  
Jose L. Zafra ◽  
Justin R. DeFrancisco ◽  
...  
Keyword(s):  
Electron Transfer ◽  
Excited State ◽  
Excited States ◽  
Transfer Process ◽  
Comprehensive Understanding ◽  
Electron Transfer Process ◽  
Photoactive Materials ◽  
Donor Acceptor ◽  
Scientific Significance

Abstract The scientific significance of excited-state aromaticity concerns with the elucidation of processes and properties in the excited states. Here, we focus on TMTQ, an oligomer composed of a central 1,6-methano[10]annulene and 5-dicyanomethyl-thiophene peripheries (acceptor-donor-acceptor system), and investigate a two-electron transfer process dominantly stabilized by an aromatization in the low-energy lying excited state. Our spectroscopic measurements quantitatively observe the shift of two π-electrons between donor and acceptors. It is revealed that this two-electron transfer process accompanies the excited-state aromatization, producing a Baird aromatic 8π core annulene in TMTQ. Biradical character on each terminal dicyanomethylene group of TMTQ allows a pseudo triplet-like configuration on the 8π core annulene with multiexcitonic nature, which stabilizes the energetically unfavorable two-charge separated state by the formation of Baird aromatic core annulene. This finding provides a comprehensive understanding of the role of excited-state aromaticity and insight to designing functional photoactive materials.

scholarly journals Light-driven deracemization enabled by excited-state electron transfer

Science ◽  
2019 ◽  
Vol 366 (6463) ◽  
pp. 364-369 ◽  
Author(s):  
Nick Y. Shin ◽  
Jonathan M. Ryss ◽  
Xin Zhang ◽  
Scott J. Miller ◽  
Robert R. Knowles
Keyword(s):  
Electron Transfer ◽  
Excited State ◽  
Hydrogen Atom ◽  
Visible Light ◽  
Asymmetric Synthesis ◽  
Hydrogen Atom Transfer ◽  
Product Distributions ◽  
Reaction Proceeds ◽  
Molecular Catalysts ◽  
Distinct Approach

Deracemization is an attractive strategy for asymmetric synthesis, but intrinsic energetic challenges have limited its development. Here, we report a deracemization method in which amine derivatives undergo spontaneous optical enrichment upon exposure to visible light in the presence of three distinct molecular catalysts. Initiated by an excited-state iridium chromophore, this reaction proceeds through a sequence of favorable electron, proton, and hydrogen-atom transfer steps that serve to break and reform a stereogenic C–H bond. The enantioselectivity in these reactions is jointly determined by two independent stereoselective steps that occur in sequence within the catalytic cycle, giving rise to a composite selectivity that is higher than that of either step individually. These reactions represent a distinct approach to creating out-of-equilibrium product distributions between substrate enantiomers using excited-state redox events.

scholarly journals Excited-state proton-coupled electron transfer within ion pairs

2020 ◽  
Vol 11 (13) ◽  
pp. 3460-3473 ◽  
Author(s):  
Wesley B. Swords ◽  
Gerald J. Meyer ◽  
Leif Hammarström
Keyword(s):  
Electron Transfer ◽  
Excited State ◽  
Ion Pairs ◽  
Proton Coupled Electron Transfer ◽  
General Method ◽  
Salicylate Ion

Electrostatic ion pairs provide a general method to study excited-state proton-coupled electron transfer. A PTaETb mechanism is identified for the ES-PCET oxidation of salicylate within photoexcited cationic ruthenium–salicylate ion pairs.

Fluorescence Enhancement of a Microbial Rhodopsin via Electronic Reprogramming

2018 ◽  
Author(s):  
Maria del Carmen Marin ◽  
Damianos Agathangelou ◽  
Yoelvis Orozco-González ◽  
Alessio Valentini ◽  
Yoshitaka Kato ◽  
...  
Keyword(s):  
Excited State ◽  
Quantum Yield ◽  
Excited States ◽  
Fluorescence Quantum Yield ◽  
Fluorescence Enhancement ◽  
Energy Surface ◽  
Wild Type ◽  
Excited State Lifetime ◽  
State Potential ◽  
Microbial Rhodopsin

The manuscript reports on two mutations of the photo-sensory protein Anabaena Sensory Rhodopsin and how these mutations modify the fluorescence quantum yield with respect to the wild-type protein. Experimental results are presented and explained theoretically on the basis of mixing of the S1 and S2 excited states. This mixing modulated by electrostatic and steric effects, tunes the excited state potential energy surface, and thereby the excited state lifetime and the fluorescence quantum yield.<br>

Light-Driven Deracemization Enabled by Excited-State Electron Transfer

2019 ◽  
Author(s):  
Nick Shin ◽  
Jonathan Ryss ◽  
Xin Zhang ◽  
Scott Miller ◽  
Robert Knowles
Keyword(s):  
Electron Transfer ◽  
Excited State ◽  
Hydrogen Atom ◽  
Visible Light ◽  
Hydrogen Atom Transfer ◽  
Catalytic Cycle ◽  
Product Distributions ◽  
Reaction Proceeds ◽  
New Strategy ◽  
Molecular Catalysts

A new strategy for catalytic deracemization is presented, wherein amine derivatives undergo spontaneous optical enrichment upon exposure to visible light in the presence of three distinct molecular catalysts. Initiated by an excited-state iridium chromophore, this reaction proceeds <i>via </i>a sequence of favorable electron, proton, and hydrogen atom transfer steps that serve to break and reform a stereogenic C–H bond. The enantioselectivity in these reactions is jointly determined by two independent stereoselective steps that occur in sequence within the catalytic cycle, giving rise to a composite selectivity that is higher than that of either step individually. These reactions represent a distinct and potentially general approach to creating out-of-equilibrium product distributions between substrate enantiomers using excited-state redox events.

scholarly journals Excited states of protonated DNA/RNA bases

2014 ◽  
Vol 16 (22) ◽  
pp. 10643-10650 ◽  
Author(s):  
Matias Berdakin ◽  
Géraldine Féraud ◽  
Claude Dedonder-Lardeux ◽  
Christophe Jouvet ◽  
Gustavo A. Pino
Keyword(s):  
Excited State ◽  
Excited States ◽  
Tautomeric Form ◽  
Excited State Lifetime ◽  
Rna Bases

The excited state lifetime of protonated DNA/RNA bases is strongly dependent on the tautomeric form.

scholarly journals Improving photosensitization for photochemical CO2-to-CO conversion

2020 ◽  
Vol 7 (9) ◽  
pp. 1459-1467
Author(s):  
Ping Wang ◽  
Ru Dong ◽  
Song Guo ◽  
Jianzhang Zhao ◽  
Zhi-Ming Zhang ◽  
...  
Keyword(s):  
Electron Transfer ◽  
Excited State ◽  
Driving Force ◽  
Cobalt Catalyst ◽  
Co2 Reduction ◽  
Excited State Lifetime ◽  
Turnover Number ◽  
Co Conversion ◽  
First Time ◽  
Insight Into

Abstract Inspired by nature, improving photosensitization represents a vital direction for the development of artificial photosynthesis. The sensitization ability of photosensitizers (PSs) reflects in their electron-transfer ability, which highly depends on their excited-state lifetime and redox potential. Herein, for the first time, we put forward a facile strategy to improve sensitizing ability via finely tuning the excited state of Ru(II)-PSs (Ru-1–Ru-4) for efficient CO2 reduction. Remarkably, [Ru(Phen)2(3-pyrenylPhen)]2+ (Ru-3) exhibits the best sensitizing ability among Ru-1–Ru-4, over 17 times higher than that of typical Ru(Phen)32+. It can efficiently sensitize a dinuclear cobalt catalyst for CO2-to-CO conversion with a maximum turnover number of 66 480. Systematic investigations demonstrate that its long-lived excited state and suitable redox driving force greatly contributed to this superior sensitizing ability. This work provides a new insight into dramatically boosting photocatalytic CO2 reduction via improving photosensitization.

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