title: Multistep π dimerization of tetrakis(n-decyl)heptathienoacene radical cations: a combined experimental and theoretical study.
abstract: Radical cations of a heptathienoacene α,β-substituted with four n-decyl side groups (D4T7(.) (+) ) form exceptionally stable π-dimer dications already at ambient temperature (Chem. Comm. 2011, 47, 12622). This extraordinary π-dimerization process is investigated here with a focus on the ultimate [D4T7(.) (+) ]2 π-dimer dication and yet-unreported transitory species formed during and after the oxidation. To this end, we use a joint experimental and theoretical approach that combines cyclic voltammetry, in situ spectrochemistry and spectroelectrochemistry, EPR spectroscopy, and DFT calculations. The impact of temperature, thienoacene concentration, and the nature and concentration of counteranions on the π-dimerization process is also investigated in detail. Two different transitory species were detected in the course of the one-electron oxidation: 1) a different transient conformation of the ultimate [D4T7(.) (+) ]2 π-dimer dications, the stability of which is strongly affected by the applied experimental conditions, and 2) intermediate [D4T7]2 (.) (+) π-dimer radical cations formed prior to the fully oxidized [D4T7]2 (.) (+) π-dimer dications. Thus, this comprehensive work demonstrates the formation of peculiar supramolecular species of heptathienoacene radical cations, the stability, nature, and structure of which have been successfully analyzed. We therefore believe that this study leads to a deeper fundamental understanding of the mechanism of dimer formation between conjugated aromatic systems.
authors.affiliation: Department of Physical Chemistry, University of Málaga, Campus de Teatinos s/n, Málaga 29071 (Spain), Fax: (+34) 952132000.
authors.forename: Cristina Capel
authors.initials: CC
authors.lastname: Ferrón
authors.forename: Marçal
authors.initials: M
authors.lastname: Capdevila-Cortada
authors.forename: Russell
authors.initials: R
authors.lastname: Balster
authors.forename: František
authors.initials: F
authors.lastname: Hartl
authors.forename: Weijun
authors.initials: W
authors.lastname: Niu
authors.forename: Mingqian
authors.initials: M
authors.lastname: He
authors.forename: Juan J
authors.initials: JJ
authors.lastname: Novoa
authors.forename: Juan T
authors.initials: JT
authors.lastname: López Navarrete
authors.forename: Víctor
authors.initials: V
authors.lastname: Hernández
authors.forename: M Carmen
authors.initials: MC
authors.lastname: Ruiz Delgado
keywords: EPR spectroscopy; density functional calculations; dimerization; oligothienoacenes; supramolecular chemistry