Aryl Shift Rearrangement in Scholl-Type Reaction Toward Nanographene.

Oxidative dehydrogenation, known as Scholl reaction, is a powerful method for synthesizing many polycyclic aromatic hydrocarbons. Sometimes, unexpected rearrangements can lead to the formation of new structures that are usually difficult to obtain. Here, we discover a novel Scholl-type reaction involving both 1,4-aryl- and 1,2-aryl shift rearrangements, resulting in the production of armchair nanographene.

Electrochemical on-surface synthesis of a strong electron-donating graphene nanoribbon catalyst.

On-surface synthesis of edge-functionalized graphene nanoribbons (GNRs) has attracted much attention. However, producing such GNRs on a large scale through on-surface synthesis under ultra-high vacuum on thermally activated metal surfaces has been challenging. This is mainly due to the decomposition of functional groups at temperatures of 300 to 500 °C and limited monolayer GNR growth based on the metal catalysis.

Deceptive orbital confinement at edges and pores of carbon-based 1D and 2D nanoarchitectures.

The electronic structure defines the properties of graphene-based nanomaterials. Scanning tunneling microscopy/spectroscopy (STM/STS) experiments on graphene nanoribbons (GNRs), nanographenes, and nanoporous graphene (NPG) often determine an apparent electronic orbital confinement into the edges and nanopores, leading to dubious interpretations such as image potential states or super-atom molecular orbitals. We show that these measurements are subject to a wave function decay into the vacuum that masks the undisturbed electronic orbital shape.

Bridging pico-to-nanonewtons with a ratiometric force probe for monitoring nanoscale polymer physics before damage.

Understanding the transmission of nanoscale forces in the pico-to-nanonewton range is important in polymer physics. While physical approaches have limitations in analyzing the local force distribution in condensed environments, chemical analysis using force probes is promising. However, there are stringent requirements for probing the local forces generated before structural damage.

Manifold dynamic non-covalent interactions for steering molecular assembly and cyclization.

Deciphering rich non-covalent interactions that govern many chemical and biological processes is crucial for the design of drugs and controlling molecular assemblies and their chemical transformations. However, real-space characterization of these weak interactions in complex molecular architectures at the single bond level has been a longstanding challenge. Here, we employed bond-resolved scanning probe microscopy combined with an exhaustive structural search algorithm and quantum chemistry calculations to elucidate multiple non-covalent interactions that control the cohesive molecular clustering of well-designed precursor molecules and their chemical reactions.

Skeletal Rearrangement of Twisted Polycyclic Aromatic Hydrocarbons under Scholl Reaction Conditions.

Treatment of a twisted polycyclic aromatic hydrocarbon containing cyclooctatetraene fused by two 9,9'-bifluorenylidene units under the Scholl reaction conditions (FeCl or 2,3-dichloro-5,6-dicyano-1,4-benzoquinone and scandium trifluoromethanesulfonate) led to stepwise skeletal rearrangements to afford initially a hydrocarbon with a seven-membered ring and then tetrabenzo[a,d,j,m]coronene with all six-membered rings. The course of the rearrangement was interpreted in terms of the acid-catalyzed isomerization of 9,9'-bifluorenylidene into dibenzo[g,p]chrysene moieties on the basis of theoretical investigations.

Light-melt adhesive based on dynamic carbon frameworks in a columnar liquid-crystal phase.

Liquid crystal (LC) provides a suitable platform to exploit structural motions of molecules in a condensed phase. Amplification of the structural changes enables a variety of technologies not only in LC displays but also in other applications. Until very recently, however, a practical use of LCs for removable adhesives has not been explored, although a spontaneous disorganization of LC materials can be easily triggered by light-induced isomerization of photoactive components.

Non-alternant non-benzenoid kekulenes: the birth of a new kekulene family.

"Kekulene" is a doughnut-like shaped polycyclic aromatic hydrocarbon consisting of cyclically arrayed benzene rings. It has attracted a great deal of theoretical interest because it is regarded as an ideal model to study conjugation circuits of π electrons, i.e.

Highly bent crystals formed by restrained π-stacked columns connected alkylene linkers with variable conformations.

A reproducible formation of strongly bent crystals was accomplished by structurally restraining macrocyclic π-conjugated molecules. The model π-units consist of two 9,10-bis(2-thienylethynyl)anthracenes with a strong propensity for stacking, which are connected in a macrocyclic fashion two alkylene linkers. The correlation between the crystalline morphology and the macrocyclic structures restrained by a variety of flexible alkylene linker combinations was systematically studied.

Tetracyclopenta[def,jkl,pqr,vwx]tetraphenylene: a potential tetraradicaloid hydrocarbon.

A tetramesityl derivative of hitherto unknown tetracyclopenta[def,jkl,pqr,vwx]tetraphenylene (TCPTP), which is a potential tetraradicaloid hydrocarbon, was synthesized. Theoretical calculations based on spin-flip time-dependent density functional theory predict that the closed-shell D2h form of TCPTP is more stable than the open-shell D4h form with its slightly tetraradical character. The tetramesityl derivative (Mes)4 -TCPTP exhibits remarkable antiaromaticity as a result of the peripheral 20-π-electron circuit, which causes an absorption maximum at a long wavelength and a small HOMO-LUMO gap.

[4.2](2,2')(2,2')Biphenylophanetriyne: a twisted biphenylophane with a highly distorted diacetylene bridge.

Biphenylophane 1 bridged by acetylene and diacetylene linkages was synthesized. X-ray analysis revealed its highly deformed diacetylene unit with a bond angle of 160°. Enantiomers of 1 resolved by chiral HPLC underwent facile racemization with an activation energy of 90.