The Effect of TCNE and TCNQ Acceptor Units on Triphenylamine-Naphthalenediimide Push-Pull Chromophore Properties

Asymmetrical and symmetrical push-pull chromophore-based on triphenylamine (TPA) donors and naphthalenediimide (NDI) acceptors are designed and successfully synthesized via [2+2] cycloaddition-retroelectrocyclization (CA-RE) reaction with well-known electron-accepting tetracyanoethylene (TCNE) and 7,7,8,8, -tetracyanoquinodimethane (TCNQ) groups. The novel series of compounds NDI-TPA-1 to NDI-TPA-6 were characterized to identify the influence of the TCNE and TCNQ pi-conjugated linkers on the optical, electrochemical, and electronic properties of these molecules. We found that in dichloromethane the NDI-TPAs 1, 4, 5, and 6 display absorbance peaks at increasing wavelengths 605, 641, 646, and 645 nm, respectively. We demonstrated that through simple chemical modification we could drop the lowest occupied molecular orbital of NDI-TPA-1 to 6. Furthermore, NDI-TPA-1 to 6 were integrated into organic thin-film transistors (OTFTs) via spin-coating technique, and charge transfer properties were investigated. We found that the choice of the functional group led to either p-type, n-type, or ambipolar characteristics.

Automated summary

The research designed and synthesized asymmetrical and symmetrical push-pull chromophores based on TPA donors and NDI acceptors, investigated the influence of TCNE and TCNQ linkers on the properties of these molecules, and studied their charge transfer characteristics in organic thin-film transistors.