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Upon combining chiral peptides (the most basic chiral source) with pyrene moieties, we found that chiral oligopeptides bearing two-pendant pyrenyl units exhibited circularly polarised luminescence (CPL) originating from intramolecular excimers at 450-490 nm in various solvents, and the sign of their CPL signals depended on the type of solvent employed. The CPL and circular dichroism signs and intensities could be tuned by the introduction of a piperidine unit into the chiral peptide chain; thus, the obtained structure could be considered a practical Lock ON-OFF system for oligopeptide luminophores.

The photoexcited and ground state chiralities of enantiopure oligopeptides bearing two pyrenyl groups (DD-2/LL-2: four methylene spacer between two pyrenyl groups and DD-1/LL-1: no methylene spacer thereof) in eight common organic solvents (CHCl3, CH2Cl2, MeOH, CH3CN, DMF, NMP, DMAc, and acetone) were investigated by means of circularly polarized luminescence (CPL) and circular dichroism (CD) spectroscopies. It was found that chiroptical signs of pyrene-origin CPL and CD signals largely depend on the nature of solvents and are susceptible to the methylene spacer. Actually, the excimer-origin CPL signs at 450–510 nm of DD-1/LL-1 in DMF were (–)/(+), respectively, while those in other solvents were oppositely (+)/(–), respectively. On the other hand, in DD-2/LL-2, the excimer-origin CPL signs were (–)/(+) in CH2Cl2 (and CHCl3), respectively, and (+)/(–) in MeOH/DMF/NMP/DMAc, respectively. The solvent dependent and the methylene spacer dependent CD sign inversion of DD-1/LL-1 and DD-2/LL-2 were also found. These results led to conclude that the solvent molecule and the methylene spacer collaboratively affect both the ground state chirality and the photoexcited chirality.

We prepared 16 novel chiral peptide–pyrene organic luminophores with different distances between the fluorescent pyrene groups and investigated their properties in CHCl3 at room temperature. The peptide–pyrene organic luminophores bearing two pyrene groups emit strong excimer circularly polarized luminescence (CPL) in the solution state. Two pendant pyrenyl groups in a series of chiral oligopeptides clearly revealed excimer CPL in chloroform at 480–490 nm (|gem| ≈ (2–8) × 10–3). When the distance between the two pyrenes increased, the sign of the CPL signals was inverted twice, while the sign of the corresponding circular dichroism (CD) signals was retained, (|gCD| ≈ (3–8) × 10–5).

The circularly polarised luminescence and circular dichroism signs of the blue circularly polarised luminescence generated by two photoexcited pyrenes as puppets are controlled by the wire structure of the C2-symmetric binaphthyl as puppeteer. The experimental results, though at variance with theoretical simulation, offer a rational design in the photoexcited and ground state chiralities of luminophores.