Tomohiko Nishiuchi

The synthesis of structurally well-defined, monodisperse carbon nanotube (CNT) sidewall segments poses a challenge in materials science. The synthesis of polyphenylene cylinders that comprise typical benzene connectivity to resemble precursors of [9,9] and [15,15] CNTs is now reported, and the products were characterized by X-ray crystallography. To investigate the oxidative cyclodehydrogenation of ring-strained molecules as a final step towards a bottom-up synthesis of CNT sidewall segments, ph

Go to three dimensions: as a step toward a bottom-up synthesis of size-defined carbon nanotubes (CNTs), [3]cyclo-4',4''''-hexaphenylbenzenes ([3]CHPBs) were synthesized and investigated. Theoretical and experimental results revealed that [3]CHPBs possess highly twisted [9]cyclo-p-phenylene cores. [3]cyclo-2,11-(Hexa-peri-hexabenzocoronene) ([3]CHBC) was also examined for CNT synthesis.

The longitudinal extension of cycloparaphenylenes (CPP) towards ultrashort carbon nanotubes (CNTs) is essential for the solution based bottom-up synthesis of CNTs. Herein, the longitudinal extension of the CPP skeleton by the introduction of hexaphenylbenzene units towards polyarylated [n]CPPs is described. Further, the applicability of the Scholl reaction to selectively form graphenic sidewalls is demonstrated. The ring size and substitution patterns of the polyarylated [n]CPPs were varied to o

The biradicaloid of Chichibabin's hydrocarbon exits in a unique thermal equilibrium between closed-shell singlet and open-shell triplet forms. Conceptually, the incorporation of nonplanar aromatic groups, such as anthraquinodimethane (AQD), in these species could bring about stabilization of the individual singlet and triplet spin biradicaloids by creating a high energy barrier for conformational interconversion between folded (singlet) and twisted (triplet) forms. Moreover, this alteration coul

All bent out of shape: The solvent of crystallization effectively enhances the emission of flexible, bent, π-conjugated molecules in the crystalline state owing to control of the packing of the molecules in the structure. Multichromism such as thermochromism and vapochromism also arises from the solvent-controlled packing. This crystalline-state emission is attributable to the flexibility of cyclooctatetraene units of the bent π-conjugated molecules in the solid state (see figure).

Novel dynamic molecular tweezers (DMTs) 3 a, 3 b, 4 a, 4 b, and 5 b, composed of two tub-shaped dibenzocyclooctatetraene (DBCOT) units, were designed and synthesized. The cyclooctatetraene (COT) rings of these DMTs readily invert in solution, and the molecular structure shows rigid syn and anti forms in an equilibrium mixture in solution. The syn and anti conformers can be observed by NMR. The isomerization barriers of 3 a, 3 b, 4 a, 4 b, and 5 b are in the range of 16.5-21.3 kcal mol(-1), depen

We prepared a new overcrowded tristricyclic aromatic ene (TAE) and investigated its external stimuli-responsive behavior for the switching between a closed-shell folded form and an open-shell twisted form. Upon photoirradiation, the folded form transforms into the biradical twisted form, whereas by keeping the twisted form in the dark, the reverse reaction gradually occurs at room temperature. This switchable conformational change is analyzed by means of UV-vis and electron spin resonance spectr

Abstract The synthesis of structurally well‐defined, monodisperse carbon nanotube (CNT) sidewall segments poses a challenge in materials science. The synthesis of polyphenylene cylinders that comprise typical benzene connectivity to resemble precursors of [9,9] and [15,15] CNTs is now reported, and the products were characterized by X‐ray crystallography. To investigate the oxidative cyclodehydrogenation of ring‐strained molecules as a final step towards a bottom‐up synthesis of CNT sidewall seg

Abstract Die longitudinale Erweiterung von Cycloparaphenylenen (CPPs) hin zu ultrakurzen Kohlenstoffnanoröhren (CNTs) ist entscheidend für die lösungsbasierte Bottom‐up‐Synthese von CNTs. In dieser Arbeit wird die longitudinale Erweiterung des CPP‐Grundgerüsts zu polyarylierten [ n ]CPPs durch die Einführung von Hexaphenylbenzoleinheiten beschrieben. Des Weiteren wird die Anwendbarkeit der Scholl‐Reaktion zum selektiven Aufbau von graphenischen Seitenwänden demonstriert. Ringgröße und Substituti

Synthesis and properties of anthracene-based cyclic π-clusters which possess two and four anthracene units are discussed. The optimal cyclization conditions were determined based on a nickel(0)-mediated reaction that afforded a cyclic anthracene dimer as the major product. Bringing two anthracene planes in close proximity in a face-to-face manner resulted in red-shifted absorption owing to the narrowing of the HOMO-LUMO gap. The cyclic anthracene dimer exhibits multi-stimuli responsiveness due t

We report variable and unique properties of 1,2-di(9-anthryl)benzene 1 as a fundamental moiety of anthracene-based π-cluster molecules. Due to a through-space π-conjugation between anthracene units, excimer emission at room temperature and charge delocalized state in radical cation state of 1 could be observed. Photoirradiation to 1 afforded an intramolecular [4 + 4] cyclized anthracene dimer 1' having a high strain energy with long C-C bond that exceeded 1.68 Å, resulting in C-C bond dissociati

This article describes bent π-conjugated systems composed of alternating o-phenylene and Z-vinylene units. all-Z-[n]Benzo[4n]annulenes are higher homologues of dibenzocyclooctatetraene (DBCOT) with a concave π system, and attempts were made to convert [20]- and [24]annulenes having partial belt structures of fullerenes and carbon nanotubes into [10]- and [12]phenacenes. A bent π-conjugated system composed of two DBCOT units showed dynamic syn-anti equilibrium in solution and behaved as dynamic m

Anthracene-attached tricyclic aromatic hydrocarbon radicals having different central polygons, Ant-5, Ant-6, and Ant-7, were synthesized to evaluate the role of an anthracene substituent group in the stability and reactivity of tricyclic aromatic hydrocarbon radicals. The bulky anthryl group effectively protects a carbon atom with high spin density, resulting in high persistence of the radicals. On the other hand, the combination of the anthryl group and the tricyclic aromatic scaffold makes the

Abstract Since the discovery of the triphenylmethyl (trityl) cation 120 years ago, a variety of aromatic cations having various colors and luminescence properties have been rigorously studied. Many, differently substituted trityl cations have been synthesized, and their optical properties have been elucidated. However, the optical properties of the parent, non‐substituted and highly reactive trityl cation, which was observed to be very weakly luminescent, have not been subjected to detailed inve

Abstract The synthesis of persistent, neutral organic radicals is challenging because of their inherent reactivities. Herein, we report the synthesis and characterization of a highly congested mesityl‐substituted tri(9‐anthryl)methyl ( TAntM ) radical ( 1 ). The scaffold was successfully synthesized by circumventing the steric hindrance imposed by the bulky groups surrounding the central methyl carbon atom. The radical has a threefold propeller structure, and the unpaired electron is mainly loca