Yasuhiro Morisaki

o-Carborane-Based Anthracene: A Variety of Emission Behaviors†

An o-carborane-based anthracene was synthesized, and single crystals, with incorporated solvent molecules, were obtained from the CHCl3 , CH2 Cl2 , and C6 H6 solutions. The anthracene ring in the crystal is highly distorted by the formation of a π-stacked dimer between the anthracene units. The crystals exhibited a variety of emission behaviors such as aggregation-induced emission (AIE), crystallization-induced emission (CIE), aggregation-caused quenching (ACQ), and multichromism.

Planar chiral tetrasubstituted [2.2]paracyclophane: optical resolution and functionalization.

We achieved optical resolution of 4,7,12,15-tetrasubstituted [2.2]paracyclophane and subsequent transformation to planar chiral building blocks. An optically active propeller-shaped macrocyclic compound containing a planar chiral cyclophane core was synthesized, showing excellent chiroptical properties such as high fluorescence quantum efficiency and a large circularly polarized luminescence dissymmetry factor.

Solid-State Emission of the Anthracene-o-Carborane Dyad from the Twisted-Intramolecular Charge Transfer in the Crystalline State

The emission process of the o-carborane dyad with anthracene originating from the twisted intramolecular charge transfer (TICT) state in the crystalline state is described. The anthracene-o-carborane dyad was synthesized and its optical properties were investigated. Initially, the dyad had aggregation- and crystallization-induced emission enhancement (AIEE and CIEE) properties via the intramolecular charge transfer (ICT) state. Interestingly, the dyad presented the dual-emissions assigned to both locally excited (LE) and ICT states in solution. From the mechanistic studies and computer calculations, it was indicated that the emission band from the ICT should be attributable to the TICT emission. Surprisingly, even in the crystalline state, the TICT emission was observed. It was proposed from that the compact sphere shape of o-carborane would allow for rotation even in the condensed state.

Synthesis of Anthracene-Stacked Oligomers and Polymer

Anthracene-stacked oligomers and a polymer were synthesized using a xanthene skeleton as the scaffold, and their structures and properties were fully characterized. Intramolecular pi-pi stacking of the anthracene rings in the ground state and excited state was observed.

Through-space conjugated polymers consisting of [2.2]paracyclophane

In this review, the synthesis and fundamental properties of [2.2]paracyclophane-containing through-space conjugated polymers are introduced. By incorporating pseudo-para-, pseudo-ortho-, and pseudo-geminal-linked [2.2]paracyclophane skeletons into conjugated polymer backbones, through-space conjugated polymers consisting of stacked π-electron systems can be prepared. Recent reports in the last two years are especially focused on conjugated polymers, and the characteristic features of the through-space conjugated polymers constructed by [2.2]paracyclophane are reviewed.

Synthesis of Optically Active, X-Shaped, Conjugated Compounds and Dendrimers Based on Planar Chiral [2.2]Paracyclophane, Leading to Highly Emissive Circularly Polarized Luminescence

Optically active, Fréchet-type dendrimers containing an emissive X-shaped π-electron system as the core unit were synthesized. Gram-scale optical resolution and transformations of 4,7,12,15-tetrasubstituted [2.2]paracyclophanes were also carried out. The high-generation dendrons effectively absorbed UV light and transferred energy to the core, resulting in high photoluminescence (PL) from the core. In addition, the dendrons sufficiently isolated the emissive X-shaped conjugated core and bright emission was observed from both thin films and solutions. Intense circularly polarized luminescence (CPL) was observed from the thin film. The dendrimer films exhibited excellent optical properties, such as large molar extinction coefficients, high fluorescence quantum efficiencies, intense PL and CPL, and large CPL dissymmetry factors.

Optically active cyclic compounds based on planar chiral [2.2]paracyclophane: extension of the conjugated systems and chiroptical properties

A series of optically active cyclic compounds based on the planar chiral tetrasubstituted [2.2]paracyclophane core were synthesized to obtain luminescent materials with excellent chiroptical properties in both the ground and excited states. The optical resolution of tetrasubstituted [2.2]paracyclophane was carried out using our previously reported method. The obtained cyclic compounds were composed of the optically active propeller-shaped structures created by the [2.2]paracyclophane core with p-phenylene–ethynylene moieties. The compounds exhibited good optical profiles, with a large molar extinction coefficient (e) and photoluminescence quantum efficiency (Φlum). The emission occurred mainly from the propeller-shaped cyclic structures. This optically active higher-ordered structure provided chiroptical properties of high performance, such as a large specific rotation ([α]D) and molar ellipticity ([θ]) in the ground state and intense circularly polarized luminescence (CPL) with large dissymmetry factors (glum) in the excited state. The results suggest that planar chiral [2.2]paracyclophane-based optically active higher-ordered structures, such as the propeller-shaped cyclic structure, are promising scaffolds for obtaining CPL and that appropriate modifications can enhance the CPL characteristics.

Colour-tunable aggregation-induced emission of trifunctional o-carborane dyes

o-Carborane compounds possessing emissive π-electron systems at the C1 and B9 (and/or B12) positions exhibit dual emission, i.e., normal emission and aggregation-induced emission (AIE). Appropriate control of the emission intensity ratio for these dyes results in colour-tunable emission from blue to orange via white.

Through-space conjugated polymers consisting of planar chiral pseudo-ortho-linked [2.2]paracyclophane

Herein, we describe the synthesis and chiroptical properties of through-space conjugated polymers with enantiopure planar chiral (R)- and (S)-pseudo-ortho-disubstituted [2.2]paracyclophane skeletons. The polymers exhibited intense circularly polarized luminescence in dilute solutions due to their conformationally stable planar chiral zigzag structures.

Planar‐Chiral Through‐Space Conjugated Oligomers: Synthesis and Characterization of Chiroptical Properties

Optically active through-space conjugated oligomers, namely, a dimer, trimer, tetramer, and cyclic trimer, consisting of a planar-chiral [2.2]paracyclophane skeleton were synthesized. In the ground state, observed similarities in the chiroptical properties of the oligomers were attributed to the equivalent orientations of two adjacent chromophores. In the excited state, the oligomers were folded into a form analogous to a one-handed helix by photoexcitation. All the compounds in dispersed solution exhibited intense circularly polarized luminescence with relatively large anisotropy factors on the order of 10(-3).