Unlike in the solution state, the circularly polarized luminescence (CPL) of the chiral oxazoline compound 4-(4-isopropyl-4,5-dihydrooxazol-2-yl)benzonitrile, having one oxazoline unit, was observed in the solid state. On the other hand, although the CPL of the chiral oxazoline compound 1,4-bis(4-isopropyl-4,5-dihydrooxazol-2-yl)benzene, having two oxazoline units, was not observed, its circular dichroism (CD) property changed significantly according to the state (i.e., solution or solid state).

A spontaneously resolved chiral fluorescent system was prepared from achiral 4-(2-arylethynyl)benzoic acid and racemic (rac)-1-phenylethylamine. Although functional chiral organic materials are usually prepared from chiral molecules, the chiral organic fluorophore described herein is successfully generated from achiral and racemic molecules to form a system that emits circularly polarized luminescence (CPL) in the solid state.

The solid-state chiral optical properties (circular dichroism and circularly polarized luminescence) of a 2-naphthalenecarboxylic acid/amine supramolecular organic fluorophore can be controlled by changing the aryl unit of the chiral 1-arylethylamine component of the molecule rather than altering the chirality of the 1-arylethylamine itself.

The solid-state chiral optical properties of a 4-(2-arylethynyl)-benzoic acid/amine supramolecular organic fluorophore can be controlled by changing the arylethynyl group of the achiral 4-(2-arylethynyl)-benzoic acid component molecule rather than the chirality of the amine component molecule.

A chiral anthracenecarboxylic acid/amine supramolecular organic fluorophore composed of a 2D layered network structure was developed by combining 1-amino-2-indanol and 2-anthracenecarboxylic acid molecules. This 2D, chiral fluorophore exhibits circularly polarized luminescence (CPL) without quenching the fluorescence in the solid state.

The cover picture shows the formation of novel functional supramolecular crystals by simple mixing/co-grinding of two component crystals. Co-grinding of crystals of 2-anthracenecarboxylic acid and (R)-1-(2-naphthyl)ethylamine produces a crystalline supramolecular organic fluorophore having a 2₁-helical columnar structure in the solid state, as observed by the change in powder X-ray diffraction patterns. Details are discussed in the article by Y. Imai, Y. Matsubara et al. on p. 1335 ff.

By using (R)-1-phenylethylamine as a chiral molecule and 1-pyrenesulfonic acid as a fluorescent molecule, a chiral supramolecular organic fluorophore composed of a 2D layered structure was successfully developed. This chiral supramolecular fluorophore possesses circularly polarized luminescence (CPL) properties in the solid state. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009)

A solid-state, chiral, helical, columnar, organic fluorophore having a π-conjugated phenylene ethynylene unit was prepared by using 4-[2-(4-methylphenyl)ethynyl]benzoic acid and 1-phenylethylamine. Such a chiral π-conjugated organic fluorophore can be obtained from achiral and racemic component molecules, and it exhibits circularly polarized luminescence (CPL) in the solid state.(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009)

A colored, two-component, supramolecular, host system has been developed. This supramolecular host system uses a charge-transfer (CT) complex composed of racemic (rac)-1,1′-bi-2-naphthol, which acts as an electron donor, and 2,5-substituted 1,4-benzoquinone, which acts as an electron acceptor. This CT host system can selectively include aromatic guest molecules into a channel-like cavity by tuning the packing of the electron-donor and electron-acceptor molecules. Characteristically, the color and diffuse reflectance spectra (DRS) of the inclusion CT complex can be tuned by changing the type of the component 2,5-substituted 1,4-benzoquinone. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009)

A novel crystalline supramolecular organic fluorophorehaving a 2₁-helical columnar structure has been prepared by solid-state co-grinding crystallization using crystals of 2-anthracenecarboxylic acid and (R)-1-(2-naphthyl)ethylamine. Although many organic fluorophores lose their fluorescence in the solid state, this supramolecular organic fluorophore exhibits fluorescence even in the solid state.(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009)

A charge-transfer (CT) complex composed of racemic rac-10,10′-dihydroxy-9,9′-biphenanthryl as the electron-donor and the diquaternary derivative of 4,4′-bipyridinium (viologen) as the electron-acceptor has been formed by the inclusion of guest molecules. The color and diffuse reflectance spectra of this inclusion CT complex are sensitive to the guest molecules, and their properties can be tuned by changing the component viologen derivatives. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008)

A solid-state fluorescent host system was created by self-assembly of a 2₁-helical columnar organic fluorophore composed of (1R,2S)-2-amino-1,2-diphenylethanol and fluorescent 1-pyrenecarboxylic acid. This host system has a characteristic 2₁-helical columnar hydrogen- and ionic-bonded network. Channel-like cavities are formed by self-assembly of this column, and various guest molecules can be included by tuning the packing of this column. Moreover, the solid-state fluorescence of this host system can change according to the included guest molecules. This occurs because of the change in the relative arrangement of the pyrene rings as they adjust to the tuning of the packing of the shared 2₁-helical column, according to the size of the included guest molecules. Therefore, this host system can recognize slight differences in molecular size and shape.