Polymeric near infrared emitters with bay-annulated indigo moieties

Abstract

Three new copolymers based on bay-annulated indigo (BAI) building blocks were synthesized through Stille-type cross-coupling reactions, alternating the electron-deficient BAI units with thiophene-based donor moieties. These polymers showed absorption and fluorescence emission in the NIR region. Their spatial structures were found to prevent aggregation-caused quenching (ACQ) in the solid state. Photoluminescence at 77 K is found ca. four times more intense than at 293 K. Based on time-resolved photoluminescence experiments, the excited-state energy transfer hopping deactivation in the copolymers is discussed in terms of a Förster-type mechanism, with time constants ranging from 10¹⁰ to 10¹¹ s⁻¹.