ON/OFF Spiroconjugation through Peripheral Functionalization: Impact on the Reactivity and Chiroptical Properties of Spirobifluorenes

Spirobifluorenes are an important class of spiro compounds frequently used in the field of organic electronics. However, harnessing spiroconjugation to obtain high‐performance in such structural motifs remains unexplored. We herein propose that peripheral functionalization may serve as a useful tool to control spiroconjugation in an ON/OFF manner on both chemical reactivity and photophysical properties. In particular, the ratio of mono‐ and di‐functionalized spirobifluorenes found experimentally during their synthesis were found to be 3/2, 7/2, and 12/2 for phenyl, nitro‐phenyl and amino‐phenyl analogues, respectively. These remarkable reactivity differences correlate with the spiroconjugation character evaluated theoretically at the CAM‐B3LYP/6‐31G(d,p) level of theory. Additionally, comparison of experimental and predicted optical and chiroptical responses shows that spiroconjugated molecular orbitals have a significant or negligible involvement on the main electronic transitions depending on the peripheral functionality of the spirobifluorene. Peripheral functionalization as a critical tool for modulating spiroconjugation in different spirobifluorene derivatives is discussed in this work. A combination of experimental and theoretical results are presented to evaluate the spiroconjugation‐reactivity and spiroconjugation‐chiroptical property relationships in spirobifluorenes, providing a springboard for molecular scaffolds with tailored spiroconjugative interactions.