Shohei Saito

The chemistry of expanded porphyrins, which are higher homologues of porphyrins, has been intensively explored for the last three decades. Expanded porphyrins exhibit structures, electronic properties, coordination chemistry, and reactivities that are entirely different from those of porphyrins. Through these studies, it has become increasingly apparent that expanded porphyrins are attractive in views of aromaticity and multimetal coordination, or as functional dyes, nonlinear optical materials,

We disclose a new planarized triarylborane in which the tri-coordinated boron atom is embedded in a fully fused polycyclic π-conjugated skeleton. The compound shows high stability toward oxygen, water, and silica gel, despite the absence of steric protection around the B atom. Reflecting the electron-donating character of the π-skeleton and the electron-accepting character of the B atom, this compound shows broad absorption bands that cover the entire visible region and a fluorescence in the vis

Abstract Die Chemie von expandierten Porphyrinen, den höheren Homologen der Porphyrine, wurde im Laufe der letzten drei Jahrzehnte ausgiebig untersucht. Expandierte Porphyrine weisen Strukturen, elektronische Eigenschaften, Reaktivitäten und ein Koordinationsverhalten auf, die sich gänzlich von denen der Porphyrine unterscheiden. Im Laufe dieser Untersuchungen wurde immer deutlicher, dass expandierte Porphyrine im Hinblick auf ihre Aromatizität und die Koordination an mehrere Metallionen oder al

Switching Aromaticity: Conformations of [32]heptaphyrins(1.1.1.1.1.1.1) are dependent upon meso-aryl substituents, solvents, temperature, and protonation. Particularly, protonation of meso-pentafluorophenyl-substituted [32]heptaphyrin triggers conformational changes to form twisted aromatic Möbius structures (see picture), even at room temperature. Detailed facts of importance to specialist readers are published as ”Supporting Information”. Such documents are peer-reviewed, but not copy-edited o

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. The difficulty of s

The preparation of boron-doped nanocarbon scaffolds with well-defined structures is important for the understanding of the impact of boron doping on their properties and behavior at the molecular level. We recently succeeded in the synthesis of a structurally well-defined nanographene molecule, bearing two boron atoms at the central positions. In this study, the characteristic properties and functions of this boron-doped nanographene were investigated in terms of (1) Lewis acidity, (2) redox pro

Polymer gels have recently attracted attention for their application in flexible devices, where mechanically robust gels are required. While there are many strategies to produce tough gels by suppressing nanoscale stress concentration on specific polymer chains, it is still challenging to directly verify the toughening mechanism at the molecular level. To solve this problem, the use of the flapping molecular force probe (FLAP) is promising because it can evaluate the nanoscale forces transmitted

The hybridization of flexible and rigid π-conjugated frameworks is a potent concept for producing new functional materials. In this article, a series of multifluorescent flapping π systems that combine a flexible cyclooctatetraene (COT) core and rigid aceneimide wings with various π-conjugation lengths has been designed and synthesized, and their structure/properties relationships have been investigated. Whereas these molecules have a V-shaped bent conformation in the ground state, the bent stru

The shape of the lowest singlet excited-state (S₁) energy profile is of primary importance in photochemistry and related materials science areas. Here we demonstrate a new approach for controlling the shape of the S₁ energy profile which relies on tuning the level of excited-state aromaticity (ESA). In a series of fluorescent π-expanded oxepins, the energy decrease accompanying the bent-to-planar conformational change in S₁ becomes less pronounced with lower ESA

An uneven split: Cooperative CuII and BIII metalation of meso-heptakis(pentafluorophenyl)[32]heptaphyrin (1) triggers an extrusion reaction to produce BIII meso-tris(pentafluorophenyl)[14]subporphyrin (2) along with a CuII porphyrin (3-Cu). Subporphyrin 2 exhibits unique optical properties that reflect the rotational restriction of its electron-withdrawing substituents. Supporting information for this article is available on the WWW under http://www.wiley-vch.de/contents/jc_2002/2007/z701682_s.p

Auf Abruf aromatisch: Die Konformationen von [32]Heptaphyrinen(1.1.1.1.1.1.1) hängen von den meso-Arylsubstituenten, dem Lösungsmittel, der Temperatur und dem Protonierungszustand ab. So führt die Protonierung von meso-Pentafluorphenyl-substituiertem [32]Heptaphyrin bei Raumtemperatur zu Konformationsänderungen, durch die verdrehte aromatische Möbius-Strukturen entstehen (siehe Bild). Detailed facts of importance to specialist readers are published as ”Supporting Information”. Such documents are

meso-Heptakis(pentafluorophenyl) heptaphyrin(1.1.1.1.1.1.1) (1) was prepared by a stepwise route in 39 % yield and its unique N-fusion reaction (NFR) sequence has been revealed; this reaction leads to singly-, doubly-, and quadruply N-fused heptaphyrins (4, 5, and 6) in good yields. These transformations are facilitated by the inherent conformational distortion of 1 as well as the distorted, folded conformations of N-fused heptaphyrins 4 and 5. The proximate arrangement of the three pyrrole unit

BBC-Neuheit: Zwei Boratome wurden mithilfe einer „Bottom-up“-Synthese in ein Kohlenstoffnanoblatt eingebaut, wobei „B-dotiertes Nanographen“ mit definierter Struktur (siehe Bild) erhalten wurde. Experimentelle und theoretische Analysen enthüllen die wesentliche Rolle der beiden Boratome für die charakteristischen Eigenschaften des Systems, z. B. die breiten Absorptionsbanden im sichtbaren Bereich und reversible Redoxprozesse.

Flapping fluorophores (FLAP) with a flexible 8π ring are rapidly gaining attention as a versatile photofunctional system. Here we report a highly photostable "flapping peryleneimide" with an unprecedented fluorogenic mechanism based on a bent-to-planar conformational change in the S₁ excited state. The S₁ planarization induces an electronic configurational switch, almost quenching the inherent fluorescence (FL) of the peryleneimide moieties. However, the FL quantum yield is

Mechanical control of the molecular energy landscape is an important issue in modern materials science. Mechanophores play a unique role in that the mechanical responses are induced against the activation barrier for intramolecular transformation with the aid of external forces. Here we report an unprecedented activation process of a flexible flapping mechanophore. Namely, thermal void collapse in a crystalline phase triggers mechanophore compression in a definite proportion. Unfavored conformat