Publications by authors named "Yasuhiro Morisaki"

Synthesis of an intrinsically chiral cofacial ABCD-Pt(II)-porphyrin (Por) dimer was achieved by the simple Pt-templated synthesis of Por, followed by Suzuki-Miyaura cross-coupling. The isolated enantiomers exhibited bright red circularly polarized phosphorescence with a value above 10 M cm.

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Optically active oligo(-phenylene)-layered molecules were synthesized from planar chiral enantiopure [2.2]paracyclophane. Their structures and optical properties were characterized by experimental and theoretical approaches.

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An optically active π-stacked molecule was synthesized incorporating planar chiral [2.2]paracyclophane and o-carborane units to impart circularly polarized luminescence and aggregation-induced emission properties to the molecule. The molecule exhibited a strong emission from the aggregated state in a mixed solvent system (HO/THF) and the solid state in the PMMA matrix.

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Since the development of the first method for porphyrin synthesis by Rothemund in 1935, porphyrin derivatives have been widely investigated and have played an essential role in chemical sciences. Most synthetic routes of porphyrins involve oxidative aromatization. Herein, we present a synthetic method to produce ABCD-porphyrins, including chiral ones, through a one-pot reaction involving "coordination, cyclization, and dehydrative aromatization" using a mono-dipyrrinatoPt(II)Cl(COE) (COE=cyclooctene) complex as a platinum template.

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Herein, we report the synthesis and chiroptical properties of 2-azatriptycenes and their platinum(II) complexes, which represent the first examples of heterotriptycenes and metallotriptycenes that exhibit circularly polarized fluorescence and phosphorescence (CPF and CPP). Theoretical studies for CPF and CPP strongly support the experimental findings.

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This study reports the synthesis of optically active cyclic tetramers comprising four stacked π-electron systems from two enantiomerically pure [2.2]paracyclophane compounds (bis-(para)-pseudo-ortho- and bis-(para)-pseudo-meta-tetrasubstituted [2.2]paracyclophane compounds).

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Article Synopsis
  • Skeletal polyhedral crystals are challenging to grow consistently due to their dynamic growth process, appearing naturally and in synthetic methods.
  • The presented methodology facilitates controlled uniaxial growth of micrometer-sized skeletal single crystals using double-decker molecules, achieved through a drop-casting technique with heated ethanol on quartz.
  • These crystals can self-assemble into specific shapes, maintain growth even after initial material is depleted, and can be structured into complex microarchitectures that function like tiny containers.
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Planar chiral [2.2]paracyclophane was employed as chiral scaffolds to twist an anthracene ring by tethering at its 1- and 8-positions; thus, twist chirality was induced in the anthracene moiety. The chiroptical properties of the resulting molecule, including circular dichroism (CD) and circularly polarized luminescence (CPL), were found to be derived from the twist chirality.

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Optically active cyclic dimer, trimer, and tetramer, in which the p-arylene-ethynylenes were stacked, were prepared using enantiopure 4,7,12,15-tetrasubstituted [2.2]paracyclophane as the chiral building block. All molecules exhibited clear Cotton effects in their absorption bands with mirror image spectra, and the signals of the longest wavelengths of the (R )- and (S )-isomers were positive and negative, respectively.

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Optically active conjugated molecules bearing one-handed helical structures, in which two [4]helicenes or two phenanthrenes are stacked at terminal benzene moieties, were prepared using enantiopure [2.2]paracyclophane as a chiral scaffold. The obtained molecules exhibited excellent chiroptical properties such as circularly polarized luminescence with high disymmetry factors.

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An optically active binuclear platinum(ii) complex based on planar chiral [2.2]paracyclophane was synthesized. The corresponding enantiomers exhibited red circularly polarized phosphorescence (CPP) with the dissymmetry factor |g| = 1.

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Article Synopsis
  • The study focuses on creating X-shaped molecules using a planar chiral [2.2]paracyclophane structure, which includes stacking di(methoxy)terphenyl units on central benzene rings.
  • At room temperature, the anisolyl rings in these molecules can freely rotate in solution, but in solid form, they are locked in place, showcasing axial chirality and propeller chirality due to intramolecular interactions.
  • The molecules exhibit notable circularly polarized luminescence (CPL) at different temperatures, with unique behavior seen at -120 °C, reflecting how the molecular structure affects their optical properties.
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A novel π-stacked polymer based on a pseudo⁻⁻linked [2.2]paracyclophane moieties was synthesized by Sonogashira-Hagihara coupling. The UV-vis absorption spectra of the synthesized polymer and model compounds revealed an extension of the conjugation length owing to the through-space conjugation.

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Planar chiral building blocks based on 4,7,12,15-tetrasubstituted [2.2]paracyclophanes were obtained via a synthetic route involving an optical resolution step. Planar chiral enantiomers, comprising two fluorophores that were stacked to form a V-shaped higher-ordered structure, were synthesized from these building blocks.

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To obtain solid-state emissive materials having stimuli-responsive luminescent chromic properties without phase transition, benzobithiophenes modified with two o-carborane units having various substituents in the adjacent phenyl ring in o-carborane were designed and synthesized. Their emission colors were strongly affected not only by the substituents at the para-position of the phenyl ring but also by molecular distribution in the solid state. In particular, the emission colors were changed by heating without crystal phase transition.

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A new type of planar chiral (R )- and (S )-4,7,12,15-tetrasubstituted [2.2]paracyclophanes was prepared from racemic 4,7,12,15-tetrabromo[2.2]paracyclophane as the starting substrate.

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Optically active phenylene-ethynylene dimers with pyridine groups based on a planar chiral 4,7,12,15-tetrasubstituted [2.2]paracyclophane were synthesized. The chiral conformation was controlled by pyridine-Ag(i) coordinations.

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Article Synopsis
  • Aryl-substituted o-carboranes have been found to exhibit highly efficient solid-state emission, leading to the synthesis of bis-o-carborane-substituted oligoacenes for color tuning of emissions.
  • Investigations showed that adding fused benzene rings reduces energy band gaps, allowing for a range of bright emissions from blue to near infrared (NIR).
  • The modified o-carboranes also demonstrated beneficial properties like aggregation-induced emission (AIE) and high quantum efficiency, with one derivative showing durability against UV photo-bleaching.
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An oxygen-bridged diphenylnaphthylamine with a helical shape was designed and synthesized as a key scaffold for circularly polarized luminescent (CPL) materials. The introduction of electron-withdrawing groups, such as formyl and 2,2-dicyanovinyl substituents at the naphthyl moiety in this skeleton effectively decreases the LUMO level and thus allows a tuning of the band gap. The prepared model compounds exhibit intense CPL signals with a dissymmetry factor (g value) of 10 both in CHCl solutions and in the solid states.

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Optically active phenylethene dimers based on a planar chiral 4,7,12,15-tetrasubstituted [2.2]paracyclophane were synthesized. We succeeded in controlling the molecular motion by binding luminophores in close proximity with the [2.

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Article Synopsis
  • The study investigates the emission characteristics of a synthesized anthracene-o-carborane dyad, focusing on its behavior in crystalline form where a twisted intramolecular charge transfer (TICT) state influences the emission process.
  • The dyad exhibits unique optical properties, including aggregation-induced and crystallization-induced emission enhancement (AIEE and CIEE) along with dual emissions in solution associated with locally excited (LE) and ICT states.
  • Mechanistic studies suggest that the TICT emission persists even when the dyad is in a crystalline state, likely due to the compact, spherical shape of o-carborane facilitating rotational movement within the solid structure.
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Phosphine is conformationally stable because of the high inversion energy barrier of the phosphorus atom, which allows the phosphorus atom to become a chiral center. Thus, enantiopure P-stereogenic 12-, 15-, 18-, and 21-membered aliphatic phosphines "diphosphacrowns" were synthesized from secondary P-stereogenic bisphosphine as a chiral building block. Their complexation behaviors with alkali metal ions are investigated in comparison with benzo-18-diphosphacrown-6 and benzo-18-crown-6.

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New types of planar chiral (Rp )- and (Sp )-4,7,12,15-tetrasubstituted [2.2]paracyclophanes were synthesized from racemic 4,12-dihydroxy[2.2]paracyclophane as the starting compound.

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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.

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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.

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