Electronic Structure of Nitrobenzene: A Benchmark Example of the Accuracy of the Multi-State CASPT2 Theory

Soto, Juan; Algarra, Manuel

doi:10.1021/acs.jpca.1c04595

Cited by 13 publications

(18 citation statements)

References 82 publications

(146 reference statements)

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“…This leads to an excellent agreement between the experimental and calculated enthalpies of dissociation. 56,57 Second, the difference between R 2 and R 1 yields an interpolation vector (Δ R ) that connects the reactants and products. Third, Δ R is divided into n segments.…”

Section: Computational Detailsmentioning

confidence: 99%

Nitrene formation is the first step of the thermal and photochemical decomposition reactions of organic azides

Soto

Algarra²,

Peláez

2022

Phys. Chem. Chem. Phys.

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Section: Computational Detailsmentioning

confidence: 99%

Nitrene formation is the first step of the thermal and photochemical decomposition reactions of organic azides

Soto

Algarra²,

Peláez

2022

Phys. Chem. Chem. Phys.

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“…In this work, we studied the reaction mechanism of the photochemical decomposition (at 520 and 350 nm, respectively) of 1-phenyl-1-diazopropane ( PDP ) and the excitation properties of its diazirine isomer, that is, 1-phenyl-1-propyl diazirine ( PED ). To this end, we have performed ab initio multiconfigurational calculations to reach qualitative and quantitative accuracy. , …”

Section: Discussionmentioning

confidence: 99%

“…To this end, we have performed ab initio multiconfigurational calculations to reach qualitative and quantitative accuracy. 44 , 45 …”

Section: Discussionmentioning

confidence: 99%

“…To achieve qualitative and quantitative accuracy, , calculations have been performed with the complete active space self-consistent field (CASSCF) − and the multistate second-order perturbation (MS-CASPT2) , methods as implemented in MOLCAS 8.4. , To avoid the inclusion of intruder states in the calculations, MS-CASPT2 energies have been calculated with an imaginary shift set to 0.1. IPEA empirical correction has been fixed at the standard value (0.25) in all of the calculations.…”

Section: Computational Detailsmentioning

confidence: 99%

“…To this end, we have performed ab initio multiconfigurational calculations to reach qualitative and quantitative accuracy. 44,45 The photochemistry of PDP and its carbene product is represented in Scheme 2. The photochemical mechanism of PDP at 520 nm (excitation to the S 1 state) is governed by a nonradiative deactivation process, which passes through a S 1 /S 0 conical intersection (CI1a or CI1b; Figure 3d,e).…”

Section: ■ Conclusionmentioning

confidence: 99%

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Photochemistry of 1-Phenyl-1-diazopropane and Its Diazirine Isomer: A CASSCF and MS-CASPT2 Study

Soto

2022

J. Phys. Chem. A

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In this work, we studied the wavelength (520 or 350 nm) dependence of the photochemical decomposition of 1-phenyl-1-diazopropane (PDP) and 1-phenyl-1-propyl diazirine (PED) by means of high-level ab initio quantum chemical calculations (CASSCF and MS-CASPT2) to obtain qualitative and quantitative results. It is found that the photochemistry of PDP is governed by nonradiative deactivation processes that can involve one or two S1/S0 conical intersections (CI1 and CI2) depending on the wavelength of the radiation; CI2 is only accessible at the shortest wavelength. It is demonstrated that the main intermediate of the photochemistry of the titled compounds is 1-ethyl-1-phenyl carbene (EPC). Upon irradiation of PDP with the 520 nm light, the carbene is always generated in its ground state as closed-shell singlet carbene. In contrast, the 350 nm radiation can directly decompose PDP into S1 carbene (open shell) and N2 when the conical intersection CI2 is avoided. Once the carbene is formed in the S1 state, it can experience excited state intramolecular proton transfer along a seam of crossing (ESIPT-SC) of the S1 and S0 states to yield the alkene derivative; that is, the proton transfer reaction takes places on a degenerate potential energy surface where the two electronic states have equal energy. In addition, it is found that EPC absorbs at 350 nm (double excitations); therefore, there is another possible route that can induce as well a slightly different photochemistry in changing the wavelength of the radiation because the shortest wavelength (when it is intense enough) decreases the amount of available EPC or generates a highly vibrationally excited state of the carbene; that is, after 350 nm excitation, the carbene intermediate can deactivate via radiation emission or can decay through a cascade of conical intersections to its first excited state (S1), where ESIPT-SC is operative again.

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Understanding of Photo‐Induced Reversible Rearrangement from Borepin to Borirane

Zhu

2022

Chemistry A European J

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The first reversible photoisomerization between a borepin and a borirane was reported in the photo‐induced reactions of B(npy)Ar2 (npy=2‐(naphthalen‐1‐yl) pyridine, Ar=phenyl or electron rich aryl; S. Wang, et al. Angew. Chem. Int. Ed. 2019, 58, 6683–6687). In this work, the detailed mechanisms of the unprecedented reversible photoisomerization between the borepin (compound a) and the borirane (compound b) of B(npy)Ph2 in the first excited singlet (S1) state and the ground (S0) state were studied by carrying out calculations with the complete active space self‐consistent field (CASSCF) and its second‐order perturbation (CASPT2) methods combined with time‐dependent density functional theory (TD‐DFT). The calculation results show that photoexcitation of a‐S0 at 365 nm and b‐S0 at 450 nm populate their S1 state with evident charge transfer characteristics. The photoisomerization is triggered in the S1 state and ends in the S0 state, at which the intersection points in a (S1/S0)x intersection seam participate in and promote phenyl migration and ring‐closure processes. Furthermore, we reveal that the not large energy difference (less than 0.6 eV) and similar conjugation properties of π electrons between a‐S0 and b‐S0 are responsible for their unique photo‐reversible reactivity, compared with those of the isomers of the thermally reversible compound B(ppy)Mes2. Our results contribute to an understanding of the excited‐state reactivity of organoboron compounds and will be useful to support the design of new boron‐based photo‐responsive materials.

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Electronic Structure of Nitrobenzene: A Benchmark Example of the Accuracy of the Multi-State CASPT2 Theory

Cited by 13 publications

References 82 publications

Nitrene formation is the first step of the thermal and photochemical decomposition reactions of organic azides

Nitrene formation is the first step of the thermal and photochemical decomposition reactions of organic azides

Photochemistry of 1-Phenyl-1-diazopropane and Its Diazirine Isomer: A CASSCF and MS-CASPT2 Study

Understanding of Photo‐Induced Reversible Rearrangement from Borepin to Borirane

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