Polycyclic aromatic hydrocarbons (PAHs) consisting of linearly fused benzene rings, namely acenes, have attracted tremendous attention due to their great potential in organic optoelectronics. The introduction of heteroatoms into the acene backbones toward heteroacenes has proven as a viable strategy for modulating their properties and functions. Furthermore, controlling the number of heteroatoms plays a vital role in precisely manipulating their electronic structures and establishing reliable structure–property relationships.

Among various heteroatoms, boron possesses a unique vacant p-orbital, thus endowing the π-conjugated system with electron-deficient character, Lewis acidity, and stimuli-responsive properties. Therefore, boron-doped acenes have attracted considerable attention, particularly due to their value as highly luminescent materials. Up to now, very few types of boron-doped acenes with only one or two boron atoms have been reported, whereas those with more than two boron atoms have remained elusive.

Recently, Xiao-Ye Wang’s group have reported the synthesis of quadruply boron-doped acenes, including tetrahydrotetraborapentacene (TBP), tetrahydrotetraboraheptacene (TBH), and tetrahydrotetraboranonacenes (TBN-Hex and TBN-iPr). These boron-doped acenes exhibit stronger Lewis acidity than the previously reported dihydrodiboraacenes, allowing for the modulation of their solid state emission properties by the formation/disassociation of Lewis acid–base adducts. Moreover, TBN-Hex, with the longest backbone, shows a loose lamella-type packing, which enables further manipulation of solid-state fluorescence by external forces. Variation of the doping level of acenes thus provides a class of tetrahydrotetraboraacenes as multicolor emissive materials. Relevant achievements were published in Nat. Commun., 2024, DOI: 10.1038/s41467-024-51806-8.

a General structure of acenes. b, c Previously reported boron-doped acenes containing one or two boron atoms. R represents various substituents. d Chemical structures of quadruply boron-doped acenes reported in this work, including tetrahydrotetraborapentacene (TBP), tetrahydrotetraboraheptacene (TBH), and tetrahydrotetraboranonacenes (TBN-Hex and TBN-iPr). Mes: 2,4,6-trimethylphenyl.