New generations of spirobifluorene regioisomers for organic electronics: tuning electronic properties with the substitution pattern

The spirobifluorene (SBF) fragment constitutes one of the most important scaffolds used in the design of Organic Semi-Conductors (OSCs) for organic electronics. In the last ten years, new generations of SBF positional isomers have appeared in the literature. The different positions of substitution (C1, C3 or C4) have allowed the tuning of the electronic properties of great interest for the further design of functional materials. The high potential of these new generations of organic semi-conductors in electronics has been demonstrated notably when they are used as host materials for Phosphorescent Organic Light-Emitting Diodes (OLEDs) or for Thermally Activated Delayed Fluorescence OLEDs. In the present feature article, we present these new generations of SBF compounds and the impact of positional isomerism on the electronic properties and device performance. Particularly, we show how the different structural and electronic parameters (nature of the linkages, bridge substitution and steric hindrance) drive the electrochemical and photophysical properties of SBF regioisomers and can be modulated. Such studies lay the foundation for material design for organic electronics.