open access

https://hdl.handle.net/2115/95591

Thermal Equilibrium Between Quinoid/Biradical Forms Enhancing Electrochemical Amphotericity

英語

Thermal equilibrium

2024-06-20

Wiley-Blackwell

Chemistry-A European journal

30(35)

e202400916

Upon dibenzo annulation on Thiele's hydrocarbon (tetraphenyl-p-quinodimethane), the quinoid form and the biradical form adopt quite different geometries, and thus are no longer resonance structures. When these two forms can interconvert rapidly due to the small energy barrier (Delta G(not equal)), the equilibrated mixture contains both forms in a ratio that is determined by the energy difference (Delta G(o)) between the two forms. For a series of tetrakis[5-(4-methoxyphenyl)-2-thienyl]-substituted derivatives, the more stable quinoid form and the metastable biradical form coexist in solution as an equilibrated mixture due to small Delta G(not equal) (<15 kcal mol(-1)) and Delta G(o) (1-4 kcal mol(-1)), in which the proportion of the two forms can be regulated by temperature. Since the biradical form can undergo easy two-electron (2e) oxidation to the corresponding dications as well as easy 2e-reduction to the dianions, it exhibits very high electrochemical amphotericity. This character with a record-small span for not only the first oxidation and reduction potentials but also the second those, [E-1(sum)approximate to E-2(sum)=E-2(ox)-E-2(red)=ca. 1.4 V], is attained through thermally enhanced conversion to the biradical form from the corresponding quinoid form, the latter of which is less amphoteric due to higher E-ox and lower E-red values.

学術雑誌論文

Accepted Manuscript

This is the peer reviewed version of the following article: Thermal Equilibrium Between Quinoid/Biradical Forms Enhancing Electrochemical Amphotericity, which has been published in final form at https://doi.org/10.1002/chem.202400916. This article may be used for non-commercial purposes in accordance with Wiley Terms and Conditions for Use of Self-Archived Versions. This article may not be enhanced, enriched or otherwise transformed into a derivative work, without express permission from Wiley or by statutory rights under applicable legislation. Copyright notices must not be removed, obscured or modified. The article must be linked to Wiley’s version of record on Wiley Online Library and any embedding, framing or otherwise making available the article or pages thereof by third parties from platforms, services and websites other than Wiley Online Library must be prohibited.

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