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Mendieta‐Moreno JI, Mallada B, de la Torre B, Cadart T, Kotora M, Jelínek P. Unusual Scaffold Rearrangement in Polyaromatic Hydrocarbons Driven by Concerted Action of Single Gold Atoms on a Gold Surface. Angew Chem Int Ed Engl 2022; 61:e202208010. [DOI: 10.1002/anie.202208010] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/31/2022] [Indexed: 11/16/2022]
Affiliation(s)
| | - Benjamin Mallada
- Institute of Physics of Czech Academy of Sciences 16200 Prague Czech Republic
- Regional Centre of Advanced Technologies and Materials Czech Advanced Technology and Research Institute (CATRIN) Palacký University Olomouc 78371 Olomouc Czech Republic
- Department of Physical Chemistry Palacký University Olomouc Str. 17. listopadu 12 771 46 Olomouc Czech Republic
| | - Bruno de la Torre
- Institute of Physics of Czech Academy of Sciences 16200 Prague Czech Republic
- Regional Centre of Advanced Technologies and Materials Czech Advanced Technology and Research Institute (CATRIN) Palacký University Olomouc 78371 Olomouc Czech Republic
| | - Timothée Cadart
- Department of Organic Chemistry Charles University 128 00 Prague 2 Czech Republic
| | - Martin Kotora
- Department of Organic Chemistry Charles University 128 00 Prague 2 Czech Republic
| | - Pavel Jelínek
- Institute of Physics of Czech Academy of Sciences 16200 Prague Czech Republic
- Regional Centre of Advanced Technologies and Materials Czech Advanced Technology and Research Institute (CATRIN) Palacký University Olomouc 78371 Olomouc Czech Republic
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Ma X, Feng E, Jiang H, Boulos VM, Gao J, Nash JJ, Kenttämaa HI. Protonated Ground-State Singlet meta-Pyridynes React from an Excited Triplet State. J Org Chem 2021; 86:3249-3260. [PMID: 33555870 DOI: 10.1021/acs.joc.0c02594] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The gaseous 2,6-didehydropyridinium cation and its derivatives transfer a proton to reagents for which the reaction for their singlet ground states is too endothermic to be observed. These reactions occur from the lowest-energy excited triplet states, which has not been observed (or reported) for other meta-benzyne analogues. Quantum chemical calculations indicate that the (excited) triplet states are stronger Brønsted acids than their (ground) singlet states, likely due to unfavorable three-center, four-electron interactions in the singlet-state conjugate bases. The cations have substantially smaller (calculated) singlet-triplet (S-T) splittings (ranging from ca. -11 to -17 kcal mol-1) than other related meta-benzyne analogues (e.g., -23.4 kcal mol-1 for the 3,5-isomer). This is rationalized by the destabilization of the singlet states (relative to the triplet states) by reduced (spatial) overlap of the nonbonding molecular orbitals due to the presence of the nitrogen atom between the radical sites (making the ring more rigid). Both the singlet and triplet states are believed to be generated upon formation of these biradicals via energetic collisions due to their small S-T splittings. It appears that once the triplet states are formed, the rate of proton transfer is faster than the rate of intersystem crossing unless the biradicals contain heavy atoms.
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Affiliation(s)
- Xin Ma
- Department of Chemistry, Purdue University, 560 Oval Drive, West Lafayette, Indiana 47907, United States
| | - Erlu Feng
- Department of Chemistry, Purdue University, 560 Oval Drive, West Lafayette, Indiana 47907, United States
| | - Hanning Jiang
- Department of Chemistry, Purdue University, 560 Oval Drive, West Lafayette, Indiana 47907, United States
| | - Victoria M Boulos
- Department of Chemistry, Purdue University, 560 Oval Drive, West Lafayette, Indiana 47907, United States
| | - Jinshan Gao
- Department of Chemistry and Biochemistry, Center for Quantitative Obesity Research, Montclair State University, 1 Normal Avenue, Montclair, New Jersey 07043, United States
| | - John J Nash
- Department of Chemistry, Purdue University, 560 Oval Drive, West Lafayette, Indiana 47907, United States
| | - Hilkka I Kenttämaa
- Department of Chemistry, Purdue University, 560 Oval Drive, West Lafayette, Indiana 47907, United States
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