Outlook and development

This article reports on a new family of molecules derived from SBF, the central molecule of organic electronics, substituted not in the para (C2) position as classically reported for over 20 years, but in the ortho (C4) position. This new 4-SBF family has only recently been described (less than ten years ago) and seems to be developing strongly. This substitution position (C4) can lead to steric hindrance between the fluorene and its substituent, manifested by a large angle between the two units and a break in conjugation between the SBF and its substituent. From the examples reported above, it can be seen that conjugation breakage can be total or partial, and that this modulation of breakage strength is an interesting route to modulating the electronic properties of 4-SBFs. Substitution of electron-rich or electron-poor groups in the C4 position can also modulate the properties of 4-SBFs...