Channels to Singlet and Triplet Phenylcarbenes in Phenyldiazomethane: A CASSCF and MRCI Study

Cui, Ganglong; Fang, Wei‐Hai

doi:10.1002/cphc.201100025

Cited by 11 publications

(6 citation statements)

References 49 publications

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“…Ground-state conformers of p -MMC and p -MMC–W are first optimized using the DFT method with the B3LYP exchange-correlation functional. − Minima, conical intersections, minimum-energy potential energy profiles, and linearly interpolated internal coordinate paths are computed using the two-root state-averaged complete active space self-consistent field (CASSCF) method, which has been shown to give a balanced description for both excited and ground electronic states in our previous applications. − In the CASSCF calculations, equal state weights are used; the active space of 10 electrons in 8 molecular orbitals is employed, which is referred to as CASSCF(10,8) hereinafter. Specifically, for the 1 ππ* state, five occupied π molecular orbitals and three unoccupied π* molecular orbitals are used, whereas for the 1 nπ* state, one occupied π molecular orbital is replaced by the n orbital of the O atom of the carbonyl group (see Supporting Information).…”

Section: Simulation Detailsmentioning

confidence: 99%

Photoprotection Mechanism of p-Methoxy Methylcinnamate: A CASPT2 Study

Chang

Xie

et al. 2015

J. Phys. Chem. A

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p-Methoxy methylcinnamate (p-MMC) shares the same molecular skeleton with octyl methoxycinnamate sunscreen. It is recently found that adding one water to p-MMC can significantly enhance the photoprotection efficiency. However, the physical origin is elusive. Herein we have employed multireference complete active space self-consistent field (CASSCF) and multistate complete active-space second-order perturbation (MS-CASPT2) methods to scrutinize the photophysical and photochemical mechanism of p-MMC and its one-water complex p-MMC-W. Specifically, we optimize the stationary-point structures on the (1)ππ*, (1)nπ*, and S0 potential energy surfaces to locate the (1)ππ*/S0 and (1)ππ*/(1)nπ* conical intersections and to map (1)ππ* and (1)nπ* excited-state relaxation paths. On the basis of the results, we find that, for the trans p-MMC, the major (1)ππ* deactivation path is decaying to the dark (1)nπ* state via the in-plane (1)ππ*/(1)nπ* crossing point, which only need overcome a small barrier of 2.5 kcal/mol; the minor one is decaying to the S0 state via the (1)ππ*/S0 conical intersection induced by out-of-plane photoisomerization. For the cis p-MMC, these two decay paths are comparable (1)ππ* deactivation paths: one is decaying to the dark (1)nπ* state via the (1)ππ*/(1)nπ* crossing point, and the second is decaying to the ground state via the (1)ππ*/S0 conical intersection. One-water hydration stabilizes the (1)ππ* state and meanwhile destabilizes the (1)nπ* state. As a consequence, the (1)ππ* deactivation path to the dark (1)nπ* state is heavily inhibited. The related barriers are increased to 5.8 and 3.3 kcal/mol for the trans and cis p-MMC-W, respectively. In comparison, the barriers associated with the photoisomerization-induced (1)ππ* decay paths are reduced to 2.5 and 1.3 kcal/mol for the trans and cis p-MMC-W. Therefore, the (1)ππ* decay paths to the S0 state are dominant relaxation channels when adding one water molecule. Finally, the present work contributes a lot of knowledge to understanding the photoprotection mechanism of methylcinnamate derivatives.

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Section: Simulation Detailsmentioning

confidence: 99%

Photoprotection Mechanism of p-Methoxy Methylcinnamate: A CASPT2 Study

Chang

Xie

et al. 2015

J. Phys. Chem. A

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“…37 Static electronic structure calculations can provide valuable insights into mechanistic photophysics and photochemistry, but they disregard dynamical effects. 38,39 A more detailed understanding of photoinduced processes requires nonadiabatic excited-state dynamics simulations. [40][41][42][43][44][45][46][47][48][49][50][51][52][53][54][55][56] In this article, we present the first such study on the truncated indigo model compound 2 (see Fig.…”

Section: Introductionmentioning

confidence: 99%

Nonadiabatic dynamics of a truncated indigo model

Cui

Thiel

2012

Phys. Chem. Chem. Phys.

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Indigo (1) is stable when exposed to ultraviolet light. We employ electronic structure calculations and nonadiabatic trajectory surface-hopping dynamics simulations to study the photoinduced processes and the photoprotection mechanism of an indigo model, bispyrroleindigo (2). Consistent with recent static ab initio calculations on 1 and 2 (Phys. Chem. Chem. Phys., 2011, 13, 1618), we find an efficient deactivation process that proceeds as follows. After vertical photoexcitation, the S(1)(ππ*) state undergoes an essentially barrierless intramolecular single proton transfer and relaxes to the minimum of an S(1) tautomer, which is structurally and energetically close to a nearby conical intersection that acts as a funnel to the S(0) state; after this internal conversion, a reverse single hydrogen transfer leads back to the equilibrium structure of the most stable S(0) tautomer. This deactivation process is completely dominant in our semiempirical OM2/MRCI nonadiabatic dynamics simulations. The other two mechanisms considered previously, namely excited-state intramolecular double proton transfer and trans-cis double bond isomerization, are not seen in any of the 325 trajectories of the present surface-hopping simulations. On the basis of the computed time-dependent populations of the S(1) state, we estimate an S(1) lifetime of about 700 fs for 2 in the gas phase.

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“…The 100 fs dynamics did not provide any compelling evidence on ISC prior to N 2 elimination. Nevertheless, drawing insights from the studies on the dissociation energy profiles of phenyl azide [43] and phenyldiazomethane, [57] we anticipate that longer time scale dynamics, initiating from singlet nitrene could contribute towards resolving the mechanism behind the formation of triplet nitrene. The analysis of structural dynamics distinguishes some of the major vibrational modes associated with the dissociation process.…”

Section: Discussionmentioning

confidence: 99%

Simulating Non‐Adiabatic Dynamics of Photoexcited Phenyl Azide: Investigating Electronic and Structural Relaxation en Route to the Formation of Phenyl Nitrene

Das,

Odelius,

Banerjee

2023

Chemistry A European J

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Excited state molecular dynamics simulations of the photoexcited phenyl azide have been performed. The semi‐classical surface hopping approximation has enabled an unconstrained analysis of the electronic and nuclear degrees of freedom which contribute to the molecular dissociation of phenyl azide into phenyl nitrene and molecular nitrogen. The significance of the second singlet excited state in leading the photodissociation has been established through electronic structure calculations, based on multiconfigurational schemes, and state population dynamics. The investigations on the structural dynamics have revealed the N − N bond separation to be accompanied by synchronous changes in the azide N − N − N bond angle. The 100 fs simulation results in a nitrene fragment that is electronically excited in the singlet manifold.

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Channels to Singlet and Triplet Phenylcarbenes in Phenyldiazomethane: A CASSCF and MRCI Study

Cited by 11 publications

References 49 publications

Photoprotection Mechanism of p-Methoxy Methylcinnamate: A CASPT2 Study

Photoprotection Mechanism of p-Methoxy Methylcinnamate: A CASPT2 Study

Nonadiabatic dynamics of a truncated indigo model

Simulating Non‐Adiabatic Dynamics of Photoexcited Phenyl Azide: Investigating Electronic and Structural Relaxation en Route to the Formation of Phenyl Nitrene

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