Ryohei Yamakado

Self-Assembly of Oligothiophene Chromophores by m-Calix[3]amide Scaffold

m-Calix[3]amides carrying the bithiophene chromophore (BTC3A) and terthiophene chromophore (TTC3A) were synthesized by the cyclic trimerization of m-aminobenzoic acid esters for the purpose of the control and understanding of the self-assembly of oligothiophene chromophores. Polymers and model compounds were also prepared for comparison. From the (1)H NMR experiments, cyclic trimer BTC3A showed the syn/anti equilibrium in solution, and the syn/anti conformer ratio (76/24 in CDCl(3)) was influenced by the solvent character. Namely, the population of the syn conformer was lowest (70%) in THF-d(8) and was highest (86%) in CDCl(3)/CD(3)OD (1/1 in volume). On the other hand, the population of the syn conformer of cyclic trimer TTC3A was high (84%) even in CDCl(3). In a CHCl(3) solution of cyclic trimer BTC3A, the absorption maximum (342 nm) blue-shifted and the emission maximum (448 nm) red-shifted compared with those of polymer BTPA and model compound BTM. The solvent character also had an impact on the optical properties of cyclic trimer BTC3A. The red-shifted emission maximum (481 nm) of cyclic trimer BTC3A in CH(3)OH indicated the interaction between three bithiophene chromophores. The emission maxima of cyclic trimer TTC3A (486 nm) demonstrated a small red-shift from model compound TTM (477 nm), and no solvent dependency was observed, unlike cyclic trimer BTC3A.

π-Electron Systems That Form Planar and Interlocked Anion Complexes and Their Ion-Pairing Assemblies.

Interactions between designed charged species are important for the ordered arrangements of π-electron systems in assembled structures. As precursors of π-electron anion units, new arylethynyl-substituted dipyrrolyldiketone boron complexes, which showed anion-responsive behavior, were synthesized. They formed a variety of receptor-anion complexes ([1+1] and [2+1] types) in solution, and the stabilities of these complexes were discussed in terms of their thermodynamic parameters. Solid-state ion-pairing assemblies of [1+1]- and [2+1]-type complexes with countercations were also revealed by single-crystal X-ray analysis. In particular, a totally charge-segregated assembly was constructed based on negatively and positively charged layers fabricated from [2+1]-type receptor-anion complexes and tetrabutylammonium cations, respectively. Furthermore, the [1+1]-type anion complex of the receptor possessing long alkyl chains exhibited mesophases based on columnar assembled structures with contributions from charge-by-charge and charge-segregated arrangements, which exhibited charge-carrier transporting properties.

Helicity Induction in Three π‐Conjugated Chromophores by Planar Chirality of Calixamide

Shall we twist? Three-dimensional arrangement of π-conjugated chromophores with triple-stranded helicity was achieved by using the planar chirality of m-calix[3]amide. Based on spectroscopic data and theoretical calculations, the dynamic and preferred helical characters of bithiophene units embedded in the tubular molecule were elucidated, and the absolute configuration was determined.

Ion-Pairing Crystal Polymorphs of Interlocked [2 + 1]-Type Receptor–Anion Complexes

The formation of a solid-state totally charge-segregated assembly (polymorph A) of negatively charged layers comprising [2 + 1]-type Cl(-) complexes of an arylethynyl-substituted dipyrrolyldiketone boron complex and positively charged layers of tetrabutylammonium (TBA) cations has already been reported. The formation of two new crystalline polymorphs (polymorphs B and C), in addition to polymorph A, is reported in this study. Both polymorphs B and C formed charge-by-charge assemblies, and the dihedral angles between two receptor units in the interlocked complexes depended on the geometries of TBA cations and the resulting packing structures. Two nonorthogonally arranged planes induced P- and M-form chiral geometries, providing diverse arrangements of chiral species according to crystal polymorphs. Furthermore, the stabilities of the three polymorphs were examined by interfragment interaction energies, which were calculated by ab initio electronic structure calculations using the fragment molecular orbital (FMO) method.

Carboxylate-Driven Supramolecular Assemblies of Protonated meso-Aryl-Substituted Dipyrrolylpyrazoles

Dipyrrolylpyrazole (dpp) derivatives possessing an aryl ring at the pyrazole 4-position were synthesized. Upon protonation, modified dpp derivatives formed a variety of assembled structures through complexation with carboxylates, as observed by single-crystal X-ray and synchrotron XRD analyses. In particular, the complexation of protonated dpp species possessing long alkyl chains with dicarboxylates resulted in highly ordered assembled structures, the packing modes of which as lamellar structures were controlled by the lengths of the spacer units between two carboxylate moieties. The charge-carrier transporting properties of the solid materials were also controlled by bound anions, including dicarboxylates.

Synthesis, reaction, and optical properties of cyclic oligomers bearing 9,10-diphenylanthracene based on an aromatic tertiary amide unit

Novel cyclic aromatic amide oligomers containing highly fluorescent 9,10-diphenylanthracene units were prepared by condensation of a monomer with amino and ester functional groups using lithium bis(trimethylsilyl)amide. The cyclic trimer (C3A, 40%) and tetramer (C4A, 8%) were isolated using preparative gel permeation chromatography. Some of the aromatic proton signals derived from anthracene were observed in the upfield region (6.96–6.87 ppm) in the 1H nuclear magnetic resonance spectrum of C3A. X-ray crystallographic analysis indicated that three anthracene moieties are inclined with respect to the cyclic skeleton and partly overlap each other. The fluorescence peak maximum of C3A (438 nm) showed a small red-shift compared with that of an acyclic model compound (425 nm). Reduction of the amide carbonyl group in C3A gave the cyclic trimer HC3A, which has a tertiary amine unit. The fluorescence peak maximum of HC3A (489 nm) was largely red-shifted from that of C3A and exhibited strong solvent dependence. A linear correlation was observed between the Stokes shift (Δν), ranging from 2981 to 6646 cm−1, and the Reichardts solvent polarity parameter [ET(30)].

Photo-Responsive Soft Ionic Crystals: Ion-Pairing Assemblies of Azobenzene Carboxylates

This report delineates the design and synthesis of negatively charged azobenzene derivatives that form photo-responsive ion-pairing assemblies. The azobenzene carboxylates possessing aliphatic chains were prepared as photo-responsive anions that promote the formation of ion-pairing dimension-controlled assemblies, including mesophases, when used in conjunction with a tetrabutylammonium (TBA) cation. The photo-responsive properties of the ion pairs and the precursory carboxylic acids in the bulk state were examined by polarized optical microscopy (POM) and X-ray diffraction (XRD), demonstrating that liquid crystal (LC)-liquid and crystal-liquid phase transitions occurred, depending on the number and lengths of the aliphatic chains of each assembly. An ion pair exhibited photo-induced crystal-crystal phase transitions upon switching between two irradiation wavelengths (365/436 nm).