Asymmetric Dual-State Emitters Featuring Thiazole Acceptors

Abstract

This work describes a new approach to construct highly conjugated molecules with asymmetric donor-acceptor-donor’ architectures (D−A−D’). Five new emissive compounds featuring thiazole, a scarcely used acceptor, were synthesized using a three-component Rh(II) catalytic reaction. The asymmetric fluorescent compounds show significant emission in solution (QY=73 %–100 %) and the solid-state (QY=14 %–59 %), and therefore considered Dual-State Emitters (DSE). We also evaluate the impact of O-alkyl chains with varying lengths in the photophysical properties in solution, aggregates, and solid-state. Computational studies indicate that the involved electronic transitions have a significant charge transfer character produced almost exclusively from the triphenylamine donors. According to the single crystal X-ray data of compounds 8 and 9, the conjugated structures have a twisted molecular conformation that contributes to the observed emission in the solid-state. These findings show a systematic approach to design DSE materials, which may help to stimulate their use in biological or optoelectronic applications.