Oligothiophene Tetracyanobutadienes: Alternative Donor−Acceptor Architectures for Molecular and Polymeric Materials

Abstract

Oligothiophene-substituted 1,1,4,4-tetracyanobutadienes (TCBDs) have been synthesized by [2 þ 2] cycloaddition reactions between tetracyanoethylene and oligothiophene alkynes. The TCBD moiety is compared to other electron acceptors attached to dibutylterthiophene including dicyanovinyl (DCV) and tricyanovinyl (TCV). These donor-acceptor molecules (TCBD-3T, DCV-3T, and TCV-3T) show red-shifted absorption spectra relative to the unsubstituted oligothiophene as a result of intramolecular charge-transfer (ICT). Monosubstituted terthiophenes bearing the electron acceptors show both oxidation and reduction processes as characterized by cyclic voltammetry. Density functional theory (DFT) calculations are used to explain the electronic and redox properties of the materials. Electrochemical oxidation of a bis(terthienyl)-substituted TCBD molecule (3T-TCBD-3T) yields a conducting polymer exhibiting balanced ambipolar redox conduction with similar values for the oxidized and reduced states of the polymer (1 Â 10 -3 S cm -1 ). Raman spectra of the asymmetric donor-acceptor materials are characterized by two intense bands characteristic of the aromatic and quinoidal regions in the conjugated π-system of the oligothiophene.

The [2+2] Cycloaddition‐Retroelectrocyclization (CA‐RE) Click Reaction: Facile Access to Molecular and Polymeric Push‐Pull Chromophores

“…Thealkyne directly attached to the phenothiazine nitrogen atom reacted with TCNE at 20 8 8C (Table 1, entry 6). [23] This result indicates that oligothiophenes have as tronger electron-donating power than monothiophene. [23] This result indicates that oligothiophenes have as tronger electron-donating power than monothiophene.…”

“…[22] Although monothiophene-substituted alkynes did not react with TCNE at 20 8 8C, at erthiophene donor afforded the TCBD compound in 59 %y ield at 20 8 8C ( Table 1, entry 7). [23] This result indicates that oligothiophenes have as tronger electron-donating power than monothiophene. Te trathiafulvalene (TTF) and extended TTF derivatives showed as imilar activity to monothiophene.H eating to reflux in 1,2-dichloroethane was necessary for the reaction to proceed, and the TCBD products were obtained in moderate yields (Table 1, entries 8a nd 9).…”

Effects of π-Conjugated Bridges on Photovoltaic Properties of Donor-π-Acceptor Conjugated Copolymers

“…These images provide further evidence of the formation of well-defined D-π-A structure and the intramolecular charge transfer behavior of the material (i.e., the HOMO to LUMO transition is a donor to acceptor intramolecular charge transfer). 42 The calculated HOMO and LUMO level positions and band gaps of the three polymers are listed in Table 2. As can be seen, although discrepancies exist between the calculation and experimental results, the trends of variation in the HOMO and energy gaps are similar.…”

Synthesis and characterization of porphyrin‐based D‐π‐A conjugated polymers for polymer solar cells

“…As can be observed, the HOMO is delocalized along the whole π‐conjugated backbone while the LUMO is mostly concentrated on the quinoxalinoporphyrin‐based accepting groups. These images provide further evidence of the formation of well‐defined D‐π‐A structure and the ICT behavior of the material (i.e., the HOMO to LUMO transition is a donor to acceptor intramolecular charge transfer) 47. The optimized geometries are shown in Figure 6.…”