Isomeric Dibenzoheptazethrenes for Air-Stable Organic Field-Effect Transistors.

Singlet diradicaloids hold great potential as semiconductors for organic field-effect transistors (OFETs). However, their relative low material and device stabilities impede the practical applications. Here, to achieve balanced stability and performance, two isomeric dibenzoheptazethrene derivatives with singlet diradical character were synthesized in a concise manner. Benefitting from the aromatic stabilization, both compounds display a small diradical character and large singlet-triplet gap, as corroborated by variable-temperature electron paramagnetic resonance spectra, single-crystal analysis, and theoretical calculations. OFET devices based on single crystals showed a high hole mobility of 0.15 cm2  V-1  s-1 , which is the highest for zethrene-based semiconductors. Both isomers exhibited remarkable material stability in air-saturated solutions as well as excellent bias-stress and storage stability in device under ambient air.