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.

Diacenaphthylene-fused benzo[1,2-b:4,5-b′]dithiophenes: polycyclic heteroacenes containing full-carbon five-membered aromatic rings

“…This concentration dependence indicates the formation of dimers between M4 and its radical cation, [M4-M4] + , at sufficiently high concentrations. 18,20 This explanation is supported by the dominant localization of the initial anodic step on the central benzodithiophene part ( Figure S1, Supporting Information -the unsubstituted model of M4 Table S1. M2-M4 and M6 have their HOMO-LUMO band gap larger than 2.3 eV and the HOMO energy levels at about 5.10 -5.40 eV, suggesting their application as organic semiconductors in p-type organic transistors.…”

Synthesis and electronic properties of nitrogen-doped π-extended polycyclic aromatic dicarboximides with multiple redox processes

“…That can be related to the easiness to accommodate negative charges over the two naphthalimide units. S42 display the UV-Vis-NIR absorption spectra recorded during 56,57 progressive electrochemical reductions of naft-1-4 in dichloromethane in the presence of high excess of tetrabutylammonium tetrafluoroborate (Bu 4 NBF 4 ), as supporting electrolyte, in an OTTLE cell. In the case of naft-1 both spectroelectrochemical reduction and oxidation processes were recorded (Figure 7) due to its amphoteric redox behavior.…”

“…UV-Vis-NIR absorption spectra recorded during 56,57 progressive electrochemical reductions of naft-1-4 in chloroform in the presence of high excess of tetrabutylammonium tetrafluoroborate (Bu 4 NBF 4 ), as supporting electrolyte, were also performed (Figures S43-44). In this case, a similar reduction absorption pattern was obtained; however, the reduced species seem to be less stabilized in chloroform than in dichloromethane, as theoretically predicted (see Table S3), confirming the results obtained by CV.…”

Ladder-type bithiophene imide-based organic semiconductors: understanding charge transport mechanisms in organic field effect transistors

“…This mechanism is found to be strongly influenced by p-dimerization reactions of radical ions which are well-suited as models to study intermolecular spatial charge delocalization in conjugated materials. [29][30][31] Up to now, the p-dimerization reactions of radical cations have been well investigated; [32][33][34] nevertheless studies related to the intermolecular dimerization of radical anions are still limited. 31 In order to address the latter, we investigate the p-dimerization process of the BTI2-BTI5 radical anions in both solution and solidstate, and its effect on charge transport mechanisms.…”

“…Time-dependent (TD) DFT calculations successfully provide a reliable assignment of the electronic absorption spectra of the p-dimerization products, thus greatly facilitating the identification of their nature and structure. 34…”