Enhancement of Push-Pull Properties of Pentafulvene and Pentafulvalene Derivatives by Protonation at Carbon - Université de Rennes Access content directly
Journal Articles European Journal of Organic Chemistry Year : 2018

Enhancement of Push-Pull Properties of Pentafulvene and Pentafulvalene Derivatives by Protonation at Carbon

Claudine Katan
Ivo Leito
Mart Lokov
  • Function : Author
Laurent Ruhlmann

Abstract

We report visible color changes and new intense, bathochromically shifted bands in absorption spectra that reach into the near-infrared region (up to 862 nm) upon protonation of nine pentafulvene and expanded pentafulvalene derivatives. This phenomenon can only be explained by the formation of carbocations with highly delocalized charges. Solution pKa values in organic solvents were determined, making use of the method of relative basicity measurements. All seven 6-phenylpentafulvenes are weak bases, and pKa values range from 0.92 to 10.29 in acetonitrile and from 1.77 to 6.46 in 1,2-dichloroethane. For the 6-phenylfulvenes with varying para-substituents on the phenyl ring, pKa values correlate well with the Hammett parameters para. Furthermore, for most compounds, electrochemical reduction is significantly facilitated by protonation. Extensive theoretical and NMR studies strongly support the postulated protonation at carbon.
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Dates and versions

hal-01737377 , version 1 (06-01-2022)

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Sophie Haberland, Aaron D. Finke, Nicolas Kerisit, Claudine Katan, Yann Trolez, et al.. Enhancement of Push-Pull Properties of Pentafulvene and Pentafulvalene Derivatives by Protonation at Carbon. European Journal of Organic Chemistry, 2018, 2018 (6), pp.739-749. ⟨10.1002/ejoc.201800039⟩. ⟨hal-01737377⟩
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