The combined CASPT2 and CASSCF studies on photolysis of 3-thienyldiazomethane and subsequent reactions

Guan, Pei-Jie; Fang, Wei‐Hai

doi:10.1007/s00214-014-1532-3

Cited by 7 publications

(6 citation statements)

References 36 publications

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“…Therefore, the S 1 →T 1 ISC may occur via the (S 1 /T 2 /T 1 ) x crossing with the T 2 state as a bridge. The crucial roles of the S 1 /T 2 /T 1 intersection in the excited‐state relaxation dynamics of aromatic carbonyl compounds and 3‐thienyldiazomethane have been well established.…”

Section: Resultsmentioning

confidence: 99%

Insights into the Photoinduced Isomerization Mechanisms of a N,C–Chelate Organoboron Compound: A Theoretical Study

Zhu

2020

ChemPhysChem

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As the first discovered organoboron compound with photochromic property, B(ppy)Mes2 (ppy=2‐phenylpyridine, Mes=mesityl) displays rich photochemistry that constitutes a solid foundation for wide applications in optoelectronic fields. In this work, we investigated the B(ppy)Mes2 to borirane isomerization mechanisms in the three lowest electronic states (S0, S1, and T1) based on the complete active space self‐consistent field (CASSCF) and its second‐order perturbation (CASPT2) methods combined with time‐dependent density functional theory (TD‐DFT) calculations. Our results show that the photoisomerization in the S1 state is dominant, which is initiated by the cleavage of the B‐Cppy bond. After overcoming a barrier of 0.5 eV, the reaction pathway leads to a conical intersection between the S1 and S0 states (S1/S0)x, from which the decay path may go back to the reactant B(ppy)Mes2 via a closed‐shell intermediate (Int1‐S0) or to the product borirane via a biradical intermediate (Int2‐S0). Although triplet states are probably involved in the photoinduced process, the possibility of the photoisomerization in T1 state is very small owing to the weakly allowed S1→T1 intersystem crossing and the high energy barrier (0.77 eV). In addition, we found the photoisomerization is thermally reversible, which is consistent with the experimental observations.

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Section: Resultsmentioning

confidence: 99%

Insights into the Photoinduced Isomerization Mechanisms of a N,C–Chelate Organoboron Compound: A Theoretical Study

Zhu

2020

ChemPhysChem

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“…The photochemical products observed upon irradiation of the methyl- and trideuteriomethyl-substituted diazo compounds 21 and 21 - d 3 are qualitatively distinct from those observed from the unsubstituted diazo compound. The dominant products seen upon irradiation of 1-(3-thienyl)diazoethanes 21 and 21 - d 3 are 3-vinylthiophenes ( 8 and 8 - d 3 , respectively), while the dominant photoproduct seen upon irradiation of 3-thienyldiazomethane is thialmethylenecyclopropene. ,, The analogous methyl-substituted thialmethylenecyclopropene products ( 18 ) were not observed in the photochemistry of 1-(3-thienyl)diazoethanes 21 and 21 - d 3 . The computed energies of the cyclopropane-containing products ( 18 ) are significantly higher in energy, ∼46 kcal/mol, than the observed hydrogen shift products ( 8 ).…”

Section: Discussionmentioning

confidence: 99%

Photochemistry of 1-(2- and 3-Thienyl)diazoethanes: Spectroscopy and Tunneling Reaction of Triplet 1-(3-Thienyl)ethylidene

Pharr,

Esselman,

McMahon

2023

J. Org. Chem.

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Photolysis (λ > 613 nm) of 1-(3-thienyl)diazoethane (21) yields the s-E rotamer of triplet 1-(3-thienyl)ethylidene (3), as characterized by UV/vis and EPR spectroscopy. The s-Z rotamer of 3 was not observed. EPR and UV/vis signals attributed to carbene 3 decrease by approximately 50% upon standing in the dark for 68 h at 10 K. Although formally spinforbidden, an intramolecular [1,2]-hydrogen shift in triplet carbene 3 to afford singlet s-E 3-vinylthiophene (8) is presumed to occur via quantum mechanical tunneling. The behavior of the CD 3 analogue supports this interpretation. Photolysis (λ > 613 nm) of 1-(3-thienyl)diazoethane-d 3 (21-d 3 ) yields triplet 1-(3-thienyl)ethylidene-d 3 (3-d 3 ), as characterized by IR, UV/vis, and EPR spectroscopy. No change in the signal intensity of EPR and UV/vis signals of triplet 3-d 3 is observed upon standing in the dark for 68 h at 10 K. In a series of 2-substituted thienyl derivatives, irradiation of 1- 23) does not yield triplet carbene intermediates. Positioning and labeling of the methyl group proved to have a large effect on products observed for these species. 1-(2-Thienyl)diazoethane ( 22) yields the products of [1,2]-hydrogen migration, s-Z and s-E 2-vinylthiophene (7), while 22d 3 and 23 give products derived from opening of the thiophene ring.

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“…1), and the different orientation of the p* NN and p 1 * orbitals gives rise to a large SOC, in agreement with El-Sayed's rule. 64 This is different from 3-thienyldiazomethane 63 related 2-thiothymine, 65 where the strong spin-orbital interaction is due to the heavy atom effect caused by a sulphur atom. According to this mechanism, ISC at (S 1 /T 2 ) X may result in the population of the DMA-T 1 minimum after internal conversion from T 2 to T 1 .…”

Section: Triplet Carbene Formationmentioning

confidence: 92%

“…through a S 1 -T 2 -T 1 sequence. 63 Inspired by this work, we have located the (S 1 /T 2 ) X and (T 2 /T 1 ) X structures in DMA (see Fig. 2), with relative energies of 3.18 and 2.99 eV, respectively.…”

Section: Triplet Carbene Formationmentioning

confidence: 96%

Early events in the photochemistry of 5-diazo Meldrum's acid: formation of a product manifold in C–N bound and pre-dissociated intersection seam regions

Migani

Blancafort

et al. 2016

Phys. Chem. Chem. Phys.

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5-Diazo Meldrum's acid (DMA) undergoes a photo-induced Wolff rearrangement (WR). Recent gas-phase experiments have identified three photochemical products formed in a sub-ps scale after irradiation, a carbene formed after nitrogen loss, a ketene formed after WR and a second carbene formed after nitrogen and CO elimination (A. Steinbacher, et al. Phys. Chem. Chem. Phys., 2014, 16, 7290-7298). In this work, ground- and excited-state potential energy surfaces (PESs) have been investigated at the MS-CASPT2//CASSCF level. The key element of the PESs is an extended S/S conical intersection seam along the C-N dissociation coordinate. The C-N predissociated region of the seam is accessed after excitation to the bright S state, and decay paths from the seam to the three primary products have been characterized. For the ketene and carbene II products, we show two possible formation pathways, a direct and a stepwise one, which suggests that these products may be formed in a bi-modal fashion. We have also characterized two possible mechanisms for triplet formation, one occurring before C-N dissociation involving a (S/T/T) crossing region, and another one through the carbene. In contrast, excitation to S leads to a C-N bound region of the seam from where DMA regeneration or diazirine formation is possible, with a preference for the first case. The results are in good agreement with experimental data. Together with our previous work on diazonaphthoquinone, they show the importance of an extended seam in the photochemistry of α-diazoketones.

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The combined CASPT2 and CASSCF studies on photolysis of 3-thienyldiazomethane and subsequent reactions

Cited by 7 publications

References 36 publications

Insights into the Photoinduced Isomerization Mechanisms of a N,C–Chelate Organoboron Compound: A Theoretical Study

Insights into the Photoinduced Isomerization Mechanisms of a N,C–Chelate Organoboron Compound: A Theoretical Study

Photochemistry of 1-(2- and 3-Thienyl)diazoethanes: Spectroscopy and Tunneling Reaction of Triplet 1-(3-Thienyl)ethylidene

Early events in the photochemistry of 5-diazo Meldrum's acid: formation of a product manifold in C–N bound and pre-dissociated intersection seam regions

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