From Allenes to Spirobifluorenes: On the Way to Device-compatible Chiroptical Systems

The last decade has seen a huge growth in the construction of chiral systems to expand the scope of chiroptical applications. Dependence of chiroptical response on molecular conformation typically leads to low chiroptical intensities of chiral systems that feature several conformations in solution. In this respect, allenes were employed for the preparation of open and cyclic oligomers as well as molecular cages, presenting remarkable chiroptical responses in solution. Their molecular chirality was also transferred to metal surfaces, yet photoisomerization of allenes limited their further exploration. In search of a more robust chiral axis, theoretical and experimental studies confirmed that spirobifluorenes could give rise to stable systems with tailored optical and chiroptical properties. Additionally, incorporating a conformational lock into spirobifluorene cyclic architectures served as an efficient strategy towards the generation of distinct helical molecular orbitals. This review article outlines our results on developing device-compatible chiroptical systems through axially chiral allenes and spirobifluorenes. The contribution from other research groups is presented briefly.