Exploiting the Aromatic Chameleon Character of Fulvenes for Computational Design of Baird-Aromatic Triplet Ground State CompoundsVisa övriga samt affilieringar
2019 (Engelska)Ingår i: Chemistry - An Asian Journal, ISSN 1861-4728, E-ISSN 1861-471X, Vol. 14, nr 10, s. 1870-1878Artikel i tidskrift (Refereegranskat) Published
Abstract [en]
Due to the reversal in electron counts for aromaticity and antiaromaticity in the closed-shell singlet state (normally ground state, S-0) and lowest * triplet state (T-1 or T-0), as given by Huckel's and Baird's rules, respectively, fulvenes are influenced by their substituents in the opposite manner in the T-1 and S-0 states. This effect is caused by a reversal in the dipole moment when going from S-0 to T-1 as fulvenes adapt to the difference in electron counts for aromaticity in various states; they are aromatic chameleons. Thus, a substituent pattern that enhances (reduces) fulvene aromaticity in S-0 reduces (enhances) aromaticity in T-1, allowing for rationalizations of the triplet state energies (E-T) of substituted fulvenes. Through quantum chemical calculations, we now assess which substituents and which positions on the pentafulvene core are the most powerful for designing compounds with low or inverted E-T. As a means to increase the -electron withdrawing capacity of cyano groups, we found that protonation at the cyano N atoms of 6,6-dicyanopentafulvenes can be a route to on-demand formation of a fulvenium dication with a triplet ground state (T-0). The five-membered ring of this species is markedly Baird-aromatic, although less than the cyclopentadienyl cation known to have a Baird-aromatic T-0 state.
Ort, förlag, år, upplaga, sidor
Wiley-VCH Verlagsgesellschaft, 2019. Vol. 14, nr 10, s. 1870-1878
Nyckelord [en]
Baird's rule, excited state aromaticity, fulvenes, quantum chemistry, triplet state energies
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Organisk kemi
Identifikatorer
URN: urn:nbn:se:uu:diva-389826DOI: 10.1002/asia.201801821ISI: 000471307500040PubMedID: 30659757OAI: oai:DiVA.org:uu-389826DiVA, id: diva2:1339459
Forskningsfinansiär
VetenskapsrådetCarl Tryggers stiftelse för vetenskaplig forskning Wenner-Gren Stiftelserna2019-07-292019-07-292019-07-29Bibliografiskt granskad