Partially Ladder-Type Molecule-Based Donor-Acceptor Conjugated Oligomer: Synthesis and Properties

The synthesis of organic semiconductors has been extensively developed in recent years due to the opportunity to fabricate low-cost and/or large-area electronic components. Among them, ladder π-conjugated oligomers are regarded as promising materials due to their rigid coplanar structures and enhanced π-conjugation, which lead to a set of desirable properties, such as intense luminescence, high carrier mobility and environmental stability. We have recently developed new approaches to prepare the fully ladder-type conjugated oligomers utilizing the BBr3-promoted intramolecular cyclization. This method features with its fast and quantitative reaction to produce both electron-rich and electron-deficient conjugated systems with rigid planar structure. Another important development in the synthesis of πconjugated oligomers has been the utilization of donoracceptor (D-A) type architectures within the backbone. The donor-acceptor systems cause partial intramolecular charge transfer (ICT) that enables manipulation of the electronic structure, leading to low band gap semiconductors with relatively high charge carrier mobilities. In a fusion of these two concepts, we present herein the synthesis of D-A alternating cooligomer 1 where the acceptor is based on the ladder-type planar molecule prepared by the BBr3-promoted lactonization and the alkylated thiophene is used as a donor (Figure 1). The photophysical, electro-