Herein, an unprecedented switching of circularly polarized luminescence (CPL) is described for chiral 4,6-bis(1-(pyren-1-ylamino)propyl)dibenzo[b,d]furan (1). The CPL band of chiral diamine 1, which contains two pyrene rings, can be switched between the monomer and excimer emission regions under concomitant inversion of the handedness, simply by changing the concentration of the fluorophore. In contrast, the maximum photoluminescence (PL) intensity is always observed in the monomer region, regardless of the concentration. The reversal of the intensity ratio of monomer and excimer emission between PL and CPL was attributed to a stronger CPL (|g| = ∼3-4 × 10) contribution from the minor excimer component, which should exhibit an efficient chiral environment around the dimeric pyrenes.

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Poly(L‐ornithine)s having various azo‐contents in the side chains were synthesized by the water‐soluble carbodiimide procedure. The photochemical properties of the polypeptides poly[Nδ‐p‐(phenylazo)benzoyl‐L‐ornithine] (PPABLO) containing 3–77 mol% azobenzene were investigated by absorption and circular dichroism spectroscopy in hexafluoro‐2‐propanol (HFIP) or water, and in HFIP‐water or methanol‐water solvent mixtures. The photochromism of the dichroic bands of the PPABLOs containing 20–77 mol% azobenzene in the visible and ultraviolet wavelength regions was found to be mostly reversible as a function of irradiation time at different wavelengths due to the photostationary state (above 80% trans‐cis photoisomerization) of the azo aromatic moieties. The PPABLO containing 3.2 mol% azobenzene in water exhibited conformational changes from random coil to helix by the addition of methanol or sodium dodecyl sulphate (SDS). The photo‐induced conformational change was observed in HFIP‐water‐SDS solvent mixtures, while no conformational change was seen in water and HFIP‐water solvent mixtures.

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