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Computational study of the cooperative effects of nitrogen and silicon atoms on the singlet–triplet energy spacing in 1,3‐diradicals and the reactivity of their singlet states
Author(s) -
Nakamura Takeshi,
Gagliardi Laura,
Abe Manabu
Publication year - 2010
Publication title -
journal of physical organic chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.325
H-Index - 66
eISSN - 1099-1395
pISSN - 0894-3230
DOI - 10.1002/poc.1643
Subject(s) - chemistry , singlet state , diradical , intermolecular force , ring (chemistry) , reactivity (psychology) , computational chemistry , singlet fission , triplet state , molecule , photochemistry , crystallography , excited state , atomic physics , organic chemistry , physics , medicine , alternative medicine , pathology
Quantum chemical calculations were performed to investigate the cooperative effect of the nitrogen and silicon atoms on the singlet–triplet energy spacing and the reactivity of the singlet state in 1,2‐diazacyclopentane‐3,5‐diyls and 1,2‐diaza‐4‐silacyclopentane‐3,5‐diyls. The largest singlet–triplet energy gap ( ${\rm }\Delta E_{{\rm ST}}^{\rm c}$ = −36.1 kcal/mol) found so far in localized 1,3‐diradicals was in the C 2v symmetry of 4,4‐difluoro‐1,2‐diaza‐4‐silacyclopentane‐3,5‐diyl at the UB3LYP/6‐31G(d) level of theory. The cooperative effect was also found in the energy differences of singlet diradicals with the corresponding ring‐closing compounds, bicyclo[2.1.0]pentane derivatives. The singlet state of the 1,2‐diaza‐4‐silacyclopentane‐3,5‐diyls was calculated to be energetically more stable than the ring‐closing compound. The notable finding on the stability of the singlet diradicals may be attributed to the resonance structures that specifically stabilize the singlet state of diradicals. The computational studies predict that the singlet 1,2‐diaza‐4‐silacyclopentane‐3,5‐diyl is a persistent molecule under conditions without intermolecular‐trapping reagents. Copyright © 2010 John Wiley & Sons, Ltd.