14 research outputs found
Bottom-up Synthesis and Thread-in-Bead Structures of Finite (<i>n</i>,0)-Zigzag Single-Wall Carbon Nanotubes
The last remaining synthetic target of finite single-wall
carbon
nanotube models, the zigzag nanotube, has been accomplished through
bottom-up chemical synthesis. The zigzag nanotube was synthetically
accessible without constructing long-sought yet elusive cyclacene
structures but with a cycloarylene structure by devising its cutout
positions. The persistent tubular shape was also perfected in this
last model by cyclization of zigzag-shaped aromatic molecules with
a synchronous topological arrangement. The crystal structure of this
nanotube further revealed an entangled supramolecular assembly, which
showed a novel way to align nanotube molecules by utilizing their
open-end functional groups in a thread-in-bead molecular assembly
Bottom-up Synthesis and Thread-in-Bead Structures of Finite (<i>n</i>,0)-Zigzag Single-Wall Carbon Nanotubes
The last remaining synthetic target of finite single-wall
carbon
nanotube models, the zigzag nanotube, has been accomplished through
bottom-up chemical synthesis. The zigzag nanotube was synthetically
accessible without constructing long-sought yet elusive cyclacene
structures but with a cycloarylene structure by devising its cutout
positions. The persistent tubular shape was also perfected in this
last model by cyclization of zigzag-shaped aromatic molecules with
a synchronous topological arrangement. The crystal structure of this
nanotube further revealed an entangled supramolecular assembly, which
showed a novel way to align nanotube molecules by utilizing their
open-end functional groups in a thread-in-bead molecular assembly
Enhanced yet Inverted Effects of π‑Extension in Self-Assembly of Curved π‑Systems with Helicity
A sextuple helix molecule possessing
four cove regions of helicene and two axes of biaryls was synthesized.
The entropy-driven self-assembly in solution was determined by concentration-
and temperature-dependent NMR spectra, which also revealed unique
dynamics of isomerization involving structural changes at the cove
regions. Unexpectedly, the assembly retarded the isomerization in
solution, and the sextuple helix structure was rigidified
Assessment of Fullerene Derivatives as Rolling Journals in a Finite Carbon Nanotube Bearing
Conformance assessment of rolling journals in a molecular bearing has been carried out with a combination of fullerenes and finite single-wall carbon nanotube molecules through quantitative analysis of the binding affinities. Endohedral fullerenes were applicable to three-body molecular bearings with slightly weaker binding affinities. Exohedral shaft moieties on C<sub>60</sub> journals affected the binding affinities to reduce the binding constants to a considerable extent, and oval-spherical C<sub>70</sub> journals were superior in tolerating bulky shaft attachments
Asymmetric Autocatalysis Initiated by Finite Single-Wall Carbon Nanotube Molecules with Helical Chirality
An asymmetric autocatalysis reaction
was initiated by a finite
single-wall carbon nanotube molecule with helical chirality. The asymmetric
induction was initiated by the chiral environment arising from the
planar chirality of the tubular polyaromatic hydrocarbons
Stereoisomerism in Nanohoops with Heterogeneous Biaryl Linkages of <i>E/Z</i>- and <i>R/S</i>-Geometries
The
stereochemistry of cycloarylene nanohoops gives rise to unique
cyclostereoisomerism originating from hoop-shaped molecular shapes.
However, cyclostereoisomerism has not been well understood despite
the ever-increasing number of structural variants. The present work
clarifies the cyclostereoisomerism of a cyclophenanthrenylene nanohoop
possessing both <i>E/Z</i>- and <i>R/S</i>-geometries
at the biaryl linkages. Involvement of the <i>R/S</i> axial
chirality in the nanohoop leads to the deviation of the structure
from a coplanar belt shape and allows for structural variations with
51 stereoisomers with <i>E/Z</i>- and <i>R/S</i>-geometries. Experimental investigations of the dynamic behaviors
of the cyclophenanthrenylene nanohoop revealed the presence of two-stage
isomerization processes taking place separately at the <i>E/Z</i>- and <i>R/S</i>-linkages. Consequently, despite the presence
of <i>E/Z</i>-fluctuations, the <i>R/S</i> axial
chirality resulted in a separable pair of enantiomers. The structural
information reported here, such as geometric descriptors and anomalous
dynamics, may shed light on the common structures of various nanohoops
Cyclo‑<i>meta</i>‑phenylene Revisited: Nickel-Mediated Synthesis, Molecular Structures, and Device Applications
From a one-pot nickel-mediated Yamamoto-type
coupling reaction
of <i>m</i>-dibromobenzene, five congeners of [<i>n</i>]Âcyclo-<i>meta</i>-phenylenes were synthesized and fully
characterized. The [<i>n</i>]Âcyclo-<i>meta</i>-phenylenes possessed a commonly shared arylene unit and intermolecular
contacts but varied in packing structures in the crystalline solid
state. Columnar assembly of larger congeners yielded nanoporous crystals
with carbonaceous walls to capture minor protic or aliphatic solvent
molecules. The concise and scalable synthesis allowed exploration
of the macrocyclic hydrocarbons as bipolar charge carrier transport
materials in organic light-emitting diode devices
Photoinduced Electron Transfer in a Dynamic Supramolecular System with Curved π‑Structures
Photoinduced electron-transfer
processes in a carbonaceous supramolecular
combination of a tubular host and a C<sub>60</sub> guest were investigated
with time-resolved transient absorption spectra upon laser flash photolysis.
Following the formation of triplet charge-separated species via electron
transfer from the host to the guest, a rapid back electron transfer
proceeded to afford triplet C<sub>60</sub>