Circularly Polarized Room Temperature Red Phosphorescence from a [9]-Heterohelical Terrylene Diimide

Circularly polarized room temperature phosphorescence (CP-RTP) in the red region is fascinating but challenging to achieve in organic molecules. The difficulty stems from the two necessary conditions required to design such molecules. First, achieving circularly polarized luminescence, with a higher emission quantum yield in the longer wavelength region, is challenging. Second, attaining phosphorescence from such molecules under ambient conditions is difficult. Achieving both criteria together in a single molecule is ambitious. In this work, we devise a novel design strategy to realize CP-RTP from a [9]-heterohelical terrylene diimide. The designed molecule possesses helical chirality and an extended conjugation, affording chiroptical responses in the red region. Furthermore, a 4-fold increment in the dissymmetry factor has been achieved by switching the solvent polarity. To our delight, the molecule showed room temperature phosphorescence in a thin film, making it the only example of a rylene diimide based helical system exhibiting CP-RTP.