Deciphering the cryptic role of a catalytic electron in a photochemical bond dissociation using excited state aromaticity markers

Banerjee, Ambar; Halder, Debabrata; Ganguly, Gautam; Paul, Ankan

doi:10.1039/c6cp03789e

Cited by 18 publications

(18 citation statements)

References 33 publications

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“…Cao (2018) also investigated the role of ring puckering and ring opening in the photorelaxation of thiazole and isothiazole using a modified SHARC-MOLPRO interface. Banerjee, Halder, Ganguly, and Paul (2016) studied the electron-catalyzed photofragmentation of 5-phenyl-2H-tetrazole, in which upon photoexcitation, an electron is injected from one part of the molecule into another part, where bond dissociation takes place, and afterward the electron returns to its originating part of the molecule. Bellshaw et al (2017) showed that the dynamics of the CS 2 molecule is strongly affected by SOCs, as the dissociation barrier is much smaller in the triplet states than in the singlet ones.…”

Section: Sharc Application Examplesmentioning

confidence: 99%

Nonadiabatic dynamics: The SHARC approach

Mai

Marquetand

González

2018

WIREs Comput Mol Sci

384

493

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We review the Surface Hopping including ARbitrary Couplings (SHARC) approach for excited‐state nonadiabatic dynamics simulations. As a generalization of the popular surface hopping method, SHARC allows simulating the full‐dimensional dynamics of molecules including any type of coupling terms beyond nonadiabatic couplings. Examples of these arbitrary couplings include spin–orbit couplings or dipole moment–laser field couplings, such that SHARC can describe ultrafast internal conversion, intersystem crossing, and radiative processes. The key step of the SHARC approach consists of a diagonalization of the Hamiltonian including these couplings, such that the nuclear dynamics is carried out on potential energy surfaces including the effects of the couplings—this is critical in any applications considering, for example, transition metal complexes or strong laser fields. We also give an overview over the new SHARC2.0 dynamics software package, released under the GNU General Public License, which implements the SHARC approach and several analysis tools. The review closes with a brief survey of applications where SHARC was employed to study the nonadiabatic dynamics of a wide range of molecular systems.This article is categorized under: Theoretical and Physical Chemistry > Reaction Dynamics and KineticsSoftware > Simulation MethodsSoftware > Quantum Chemistry

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Section: Sharc Application Examplesmentioning

confidence: 99%

Nonadiabatic dynamics: The SHARC approach

Mai

Marquetand

González

2018

WIREs Comput Mol Sci

384

493

View full text Add to dashboard Cite

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“… 10 This triggered a renewed interest in excited-state aromaticity (ESA), both in terms of obtaining spectroscopic evidence for the concept 11 − 14 and applying it to the design of novel synthetic protocols. 15 − 17 Furthermore, this trend led to the discovery of ways of tuning ESA through steric and electronic substituent effects 18 and to the development of strategies for using ESA to modulate double-bond photoisomerization, 19 − 22 proton-transfer, 21 , 23 − 25 electrocyclization, 26 conformational-planarization, 27 − 29 and photodissociation 30 reactions.…”

Section: Introductionmentioning

confidence: 99%

Photoinduced Changes in Aromaticity Facilitate Electrocyclization of Dithienylbenzene Switches

et al. 2020

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The concepts of excited-state aromaticity and antiaromaticity have in recent years with increasing frequency been invoked to rationalize the photochemistry of cyclic conjugated organic compounds, with the long-term goal of using these concepts to improve the reactivities of such compounds toward different photochemical transformations. In this regard, it is of particular interest to assess how the presence of a benzene motif affects photochemical reactivity, as benzene is well-known to completely change its aromatic character in its lowest excited states. Here, we investigate how a benzene motif influences the photoinduced electrocyclization of dithienylethenes, a major class of molecular switches. Specifically, we report on the synthesis of a dithienylbenzene switch where the typical nonaromatic, ethene-like motif bridging the two thienyl units is replaced by a benzene motif, and show that this compound undergoes electrocyclization upon irradiation with UV-light. Furthermore, through a detailed quantum chemical analysis, we demonstrate that the electrocyclization is driven jointly and synergistically by the loss of aromaticity in this motif from the formation of a reactive, antiaromatic excited state during the initial photoexcitation, and by the subsequent relief of this antiaromaticity as the reaction progresses from the Franck–Condon region. Overall, we conclude that photoinduced changes in aromaticity facilitate the electrocyclization of dithienylbenzene switches.

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“…Indeed, intramolecular charge transfer of an electron from an excited state antiaromatic benzene ring was recently found to occur during photodissociation of a protecting group. 39,40 Now, how does the aromaticity of 2 change upon photoexcitation and subsequent ionization to the radical cation? We investigated this with calculations on the model compound 2'.…”

Section: Excited State Antiaromaticity As a Potential Driving Force Fmentioning

confidence: 99%

Degradation of Pharmaceuticals Through Sequential Photon Absorption and Photoionization – the Case of Amiloride Derivatives

Jorner¹,

Rabten²,

Slanina³

et al. 2020

Preprint

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Photodegradation of pharmaceutical and agrochemical compounds is an important concern for health and the environment. Amiloride derivatives undergo clean photosubstitution in protic solvents. We have studied this apparent photo-SNAr reaction with a range of experimental and computational techniques. Available evidence points to a mechanism starting with photoexcitation followed by absorption of a second photon to eject an electron to give a radical cation intermediate. Subsequent substitution reaction with the protic solvent is assisted by a general base, possibly strengthened by the proximal solvated electron. Final recombination with the solvated electron generates the observed product. Quantum chemical computations reveal that excited state antiaromaticity is relieved when an electron is ejected from the photoexcited molecule by the second photon, leading to a weakly aromatic radical cation. The mechanism indicated here could have wide applicability to photoinduced degradation of similar heteroaromatic compounds in the environment as well as in protic solvents. There are also strong similarities to a class of increasingly popular synthetic photoredox methods.

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Deciphering the cryptic role of a catalytic electron in a photochemical bond dissociation using excited state aromaticity markers

Cited by 18 publications

References 33 publications

Nonadiabatic dynamics: The SHARC approach

Nonadiabatic dynamics: The SHARC approach

Photoinduced Changes in Aromaticity Facilitate Electrocyclization of Dithienylbenzene Switches

Degradation of Pharmaceuticals Through Sequential Photon Absorption and Photoionization – the Case of Amiloride Derivatives

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