The research on polycyclic aromatic hydrocarbons (PAHs) gained momentum in the last decade. In particular, chiral congeners have experienced a surge in interest due to their potential for applications in chiral organic electronics. Optical and electronic properties of PAHs can be judiciously altered by incorporation of heteroatoms. Boron atoms endow the molecules with high electron affinity, improved electron mobility and photovoltaic performance. Organoboron compounds have also received recognition for their outstanding optical properties and are intensively investigated in organic light-emitting diodes. The synthetic availability of chiral boron compounds is, however, limited.<br/>In this presentation, we will report on organoboron helicenes incorporating five-membered azaborole rings. Their synthesis was executed by a modular approach from small achiral building blocks. The compounds exhibit high differential absorption of circularly-polarized light and strong fluorescence both in solution and in the solid state. These properties are particularly appealing when compared to other helicenes whose fluorescence intensity is reduced due to the intersystem crossing. We will discuss our modular approach to the synthesis of curved and chiral organoboron compounds, their optical and chiroptical properties in solution as well as solid-state emission and configurational stability. The properties of these molecules will be contrasted with the six-membered congeners and other common emitters.

Helically chiral organoboron compounds: Modular synthesis, optical properties and configurational stability

ACS Spring Meeting 2021

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