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Spin–Spin Coupling Between Two meta ‐Benzyne Moieties In a Quinolinium Tetraradical Cation Increases Their Reactivities
Author(s) -
Kotha Raghavendhar R.,
Yerabolu Ravikiran,
Ding Duanchen,
Szalwinski Lucas,
Ma Xin,
Wittrig Ashley,
Kong John,
Nash John J.,
Kenttämaa Hilkka I.
Publication year - 2019
Publication title -
chemistry – a european journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.687
H-Index - 242
eISSN - 1521-3765
pISSN - 0947-6539
DOI - 10.1002/chem.201806096
Subject(s) - aryne , moiety , chemistry , reactivity (psychology) , singlet state , hydrogen atom abstraction , medicinal chemistry , photochemistry , nucleophile , stereochemistry , computational chemistry , radical , organic chemistry , excited state , medicine , physics , alternative medicine , pathology , nuclear physics , catalysis
The reactivity of a carbon‐centered σ,σ,σ,σ‐type singlet‐ground‐state tetraradical containing two meta ‐benzyne moieties was examined in the gas phase. Surprisingly, the tetraradical showed higher reactivity than its individual meta ‐benzyne counterparts. The reactivity of meta ‐benzynes is controlled by their (calculated) distortion energy Δ E 2.3 , singlet–triplet spitting Δ E S–T , and electron affinity (EA 2.3 ) of the meta ‐benzyne moiety at the transition state geometry for hydrogen‐atom abstraction reactions. The addition of a second meta ‐benzyne moiety to a meta ‐benzyne does not significantly change EA 2.3 . However, Δ E 2.3 is substantially decreased for both meta ‐benzyne moieties in the tetraradical, and this explains their higher reactivities. The decrease in Δ E 2.3 for each meta ‐benzyne moiety in the tetraradical is rationalized by stabilizing spin–spin coupling between one radical site in each meta ‐benzyne moiety. Therefore, spin–spin coupling between the meta ‐benzyne moieties in this tetraradical increases its reactivity, whereas spin–spin coupling within each meta ‐benzyne moiety decreases its reactivity.