Organic semiconductors based on complex diarylfluorenes via Friedel-Crafts protocols of fluorenols

Steric design of organic semiconductors plays a crucial role in the improvement of device performance and behaviors. Sterically hindered semiconductors of complex diarylfluorenes (CDAFs) have been updated via the development of the Friedel-Crafts (FC) reaction of fluorenols that offer new opportunities for the preparation of their different structures and functionalization. In this review, CDAFs are highlighted at three levels including the features of fluorenol-based FC reaction, the multiscale structures of CDAFs and their various device applications in organic/plastic (opto)electronics. Firstly, simply description of the crucial role of sterically hindered semiconductors in organic/plastics electronics, followed by the history of FC reaction, the nature and advantages of fluorenol's FC reaction that involves the effects of molecular structure substrates, compatibility and synergy with other reactions and so on. Then, we highlighted various macromolecules and organic semiconductors of CDAFs, including small molecules or oligomers, polymers and nanomolecules by the design of the multi-bulk, nano-bulk, and hinder-capping approaches, which also lead to the discovery of organic nanogrids and their organic nanopolymers. Finally, we gave the applications of CDAFs in organic light-emitting diodes, organic lasers, organic solar cells, organic charge-trapping or resistance-switching memory, and molecular nanodevices. At the end, the development of diarylfluorene and heterofluorene based sterically hindered semiconductors is summarized and the perspective on the gridochemistry for organic intelligence is also addressed. FC reaction based on fluorenol has many advantages in the preparation of diarylfluorenes (CDAFs) semiconductor materials: (1) Mild reaction conditions (room temperature environment), little toxicity owing to reaction system without noble metal, and simple post-treatment; (2) a wide range of substrates; (3) the efficient method is compatible with several functional groups; (4) the steric hindrance effect of fluorenes can be effectively utilized to regulate intermolecular pstacking interactions and improve the thermal stability of products; (5) the substitution sites of aromatic substituents can be controlled by the reversible dynamic and thermodynamic characteristics; (6) molecular tailoring such as Friedel-Crafts functionalization and heteroatom substitution can be used for molecular design to construct multifunctional organic semiconductor materials. Fluorenol-based Friedel-Crafts reaction offers a new opportunity for the preparation of CDAFs with different structures and their functionalized sterically hindered semiconductors.