Molecular packing structural transition driven handedness inversion of circularly polarized luminescence of phenothiazine substituted Phe–Phe dipeptides

Abstract

A phenothiazine group was attached to a pair of Phe–Phe homochiral dipeptides with different chiralities. A structural transition from micelles to twisted nanoribbons with extending aging time was observed in a solvent mixture of HFIP and H₂O. The FT-IR and XRD results indicated that a parallel β-sheet structure existed in the packing structure, and hydrogen bonding and π–π stacking played important roles in the nanoribbon formation. The phenothiazine segment and the bridging phenylene group were twisted in one-handedness, and the molecules with a conformational chirality were stacked in a chiral manner. Circular dichroism (CD) and circularly polarized luminescence (CPL) were detected in both micelles and nanoribbons. Handedness inversion of CPL was observed when the beginning micellar structures transformed into twisted nanoribbons. The results indicated that the chirality was transferred from Phe–Phe dipeptides to the capping phenothiazine group, and the chiral stacking style dominated the handedness of self-assemblies in both the ground and the excited states.