Synthesis and n-Type Semiconducting Properties of Bis(dioxaborin) Compounds Containing a π-Extended 2,2′-Bithiophene Structure

Bis(dioxaborin) compounds containing pi-conjugated systems have been studied as n-type semiconductors for organic field-effect transistors (OFETs). In this study, with the aim of investigating the effect of the extension of the pi-conjugation on the n-type semiconducting properties and stability of bis(dioxaborin) compounds, we synthesized new compounds containing 2,2 '-bithiophene derivatives extended with an olefin or an acetylene spacer. The absorption maxima of the compounds containing olefin spacers were greatly red-shifted compared with those of the original compound without a pi-spacer. The newly synthesized compounds exhibited high electron affinity, and the olefin spacers effectively reduced the on-site Coulomb repulsion in the two-electron reduction of the compounds. An OFET fabricated using one of these compounds having a layer-by-layer crystal structure exhibited n-type semiconductor behavior with a low threshold voltage, most likely due to the small on-site Coulomb repulsion. The electron-transporting properties were investigated by theoretical calculations based on the Marcus theory.

Automated summary

In this study, bis(dioxaborin) compounds with extended pi-conjugated systems were synthesized and found to exhibit red-shifted absorption maxima, high electron affinity, and reduced on-site Coulomb repulsion in the two-electron reduction. An OFET fabricated using one of these compounds with a layer-by-layer crystal structure demonstrated n-type semiconductor behavior.