Solid-State Near-Infrared Emission of it-Conjugated Polymers Consisting of Boron Complexes with Vertically Projected Steric Substituents

The development of solid-state near-infrared (NIR)-emissive pi-conjugated polymers (CPs) has been still difficult due to lack of valid guidelines for avoiding aggregation -caused quenching. To obtain solid-state emission, we designed new strong electron acceptors by employing boron-fused azobenzene complexes with vertically projected bulky substituents at boron, which can prevent the pi-surface from intermolecular interactions. Herein, we demonstrate donor-acceptor-type CPs with NIR emission properties. In summary, the CP with a bithiophene donor bearing the bulkiest substituent exhibited excellent solid-state NIR emission (lambda FL = 806 nm, (DFL = 7.5%). In addition, the longest emission maximum was obtained from the CP containing cyclopentadithiophene (lambda FL = 923 nm, (DFL = 0.9%). The concept for the introduction of vertically projected bulky substituents at boron opens a new research field on solid-state NIR-emissive materials.