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 CHCl 3 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 (j g em j % (2-8) 3 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, (j g CD j % (3-8) 3 10 -5 ).Recently, chiral organic and organometallic luminophores that efficiently emit circularly polarized luminescence (CPL) in the near-ultraviolet, visible, and near-infrared regions have received much attention because of their potential optoelectronic and photonic applications. [1][2][3][4] However, several studies of chiral luminophores having conformational freedom have suggested that controlling photoexcited chirality is one of the most challenging, difficult issues in chiral photochemistry because the sign and absolute magnitude of the CPL signals in the photoexcited state often differ from those of the circular dichroism (CD) signals in the ground state. [3] Possibly, the limited knowledge and understanding of photoexcited-state chirality may lead to unpredictable CPL and CD characteristics, because most textbooks of stereochemistry mainly discuss the chirality of ground-and thermally excited-states. Steady-state CPL spectroscopy detects photoexcited, short-lived chiral species, whereas steady-state CD spectroscopy focuses on long-lived chiral species at ambient temperature.According to a modified Jablonski diagram of chiral luminophores, short-lived chiral species (S 1 , S 2 , …) upon photoexcitation are first generated according to the Franck-Condon scheme at~10 -15 sec, and undergo non-radiative relaxation associated with ro-vibrational modes to the lowest vibronic state (S 1 state with n = 0), at~10 -11 -10 -12 sec. These species relax to the chiral ground state with CPL radiation at~10 -9 -10 -6 sec. [3] To ensure identical chirality between the photoexcited and ground states, enantiopairs of rigid scaffolds bearing achiral luminophores can be designed when a pair of (+)-and (-)-sign CPL luminophores is needed.Several novel strategies that enable the inversion of the CPL signs of luminophores without significant changes in the chiral scaffolds have been reported. [4] These works showed that the CPL signs of chiral luminescent systems are not determined by the stereogenic centers and/or stereogenic bonds of the substances. The inversion characteristics of the CPL sign can be modified by the choice of solvent, [4a, k] host matrix, [4e] stir direction at the sol-gel transition temperature, [4b] geometrical modifications of luminophores, [4c, d, g] heating-and-cooling treatments, [4f, k] and aggregation-and-disag...

The coordination of Eu(iii) (from Eu(iii)(hfa)3) by chiral P(iii) (from BINAP) led to circularly polarised luminescence in dilute solutions on the order of |gem| ≈ 10−2 at 5D0 → F1 and |gem| ≈ 10−2 at 5D0 → F2 transitions, i.e., in chloroform and acetone.

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.

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