Linear Axially Chiral Conjugated Polymers Exhibiting Ultralong Low-Temperature Phosphorescence and Intense Circularly Polarized Luminescence.

Abstract

Ultralong organic phosphorescence (UOP) and circularly polarized luminescence (CPL), as two important branches in the field of organic optical functional materials have broad prospects. In this work, a pair of novel conjugated polymers with low-temperature UOP and intense CPL properties are constructed by incorporating rigid axially chiral chromophores into a polymeric backbone. The twisted and rigid biphenyl skeleton not only effectively reduces the energy gap between the S1 and T to greatly facilitate the intersystem crossing process, but also suppress the non-radiative decay from T1 to S0 . As a result, a strong and ultralong afterglow of up to 33 s is achieved in 2-MeTHF at 77 K. Moreover, the repeating rigid biphenyl skeleton with its helix-like form also promotes the chiroptical activity of the polymers, and intense signals are shown in the low-temperature CPL spectra with absolute glum values of 9.7×10-3 and 5.8×10-3 at the fluorescence and phosphorescence emission peaks, respectively. This work represents the first low-temperature materials with UOP and CPL properties, which provides a new guideline and perspective for the development of persistent luminescence materials.