Isomerically Pure Oxindole-Terminated Quinoids for n-Type Organic Thin-Film Transistors Enabled by the Chlorination of Quinoidal Core

Quinoidal compounds have great potential utility as high-performance organic semiconducting materials because of their rigid planar structures and extended pi-conjugation. However, the existence of E and Z isomers adversely affects the charge-transport properties of quinoidal compounds. In this study, three isomerically pure oxindole-terminated quinoids were developed by introducing chlorine atoms in the quinoidal core. The synthesized quinoids were confirmed to have a Z,Z configuration by means of H-1 NMR spectroscopy, density functional theory calculations, and single-crystal X-ray analysis. Importantly, the strategy of chlorination allowed to maintain low-lying frontier molecular orbital energy levels and ensure favorable intermolecular packing. Consequently, all three quinoidal compounds showed n-type transport characteristics in organic thin-film transistors, with electron mobilities up to 0.35 cm(2) V-1 s(-1), which is the highest value reported to date for oxindole-terminated quinoids. Our study can provide new guidelines for the design of isomerically pure quinoids with high electron mobilities.