Hydrogen-Bonding-Mediated Solid-State Self-Assembled Isoepindolidiones (isoEpi) Crystal for Organic Field-Effect Transistor

Novel pigments isoepindolidiones (isoEpi) and di-tert-butyl quinolino[8,7-h]quinoline-1,7-diyl bis(carbonate) (isoEpi-Boc) were synthesized and characterized. The spectroscopic characterizations indicated that the tert-butyloxycarbonyl (t-Boc) units could be removed from soluble isoEpi-Boc by thermal annealing, forming insoluble isoEpi with hydrogen bonding. A solid-state isoEpi-Boc crystal to isoEpi crystal transition was observed during the annealing process and the molecular packing was significantly changed. With the emergence of hydrogen bonds, the isoEpi molecules were arranged into a brick-in-wall structure with π-stacking along the crystal growth axis, leading to a significant enhancement of charge mobility along the crystal growth direction (the hole mobility from 3.4 × 10^-4 to 0.32 cm²/(V·s), and the electron mobility from nondetectable to 5.6 × 10^-3 cm²/(V·s)). The results indicate that isoEpi is a promising chromophore for organic field-effect transistor (OFET). The crystal-to-crystal transition driven by the formation of hydrogen bonds is a unique method for modulating the charge transport properties in organic semiconductive materials for OFET devices.