Periodically Twisted Molecular Wires Based on a Fused Unit for Efficient Intramolecular Hopping Transport.

Realizing efficient long-distance intramolecular charge transport based on a hopping mechanism is a key challenge in molecular electronics. In hopping transport, a smaller reorganization energy (λ) and energy difference between hopping sites (Δ) should lead to a smaller activation energy and faster charge transfer. However, the development of π-extended molecules that meet these requirements is challenging.

Colorless Near-Infrared Absorbing Dyes Based on B-N Fused Donor-Acceptor-Donor π-Conjugated Molecules for Organic Phototransistors.

The introduction of a colorless function to organic electronic devices allows responses to light in the near-infrared (NIR) region and is expected to broaden the applications of these devices. However, the development of a colorless NIR dye remains a challenge due to the lack of a rational molecular design for controlling electronic transitions. In this study, to suppress the π-π* transitions in the visible region, polycyclic donor-acceptor-donor π-conjugated molecules with boron bridges (Py-FNTz-B and IP-FNTz-B) are designed and synthesized, which contain pyrrole or indenopyrrole as donor units with fluorinated naphthobisthiadiazole (FNTz) as an acceptor unit.

Fluorinated Dihydropentalene-1,4-Dione: A Strong Electron-Accepting Unit with Organic Semiconductor Characteristics.

Invited for the cover of this issue are Soichi Yokoyama and Yutaka Ie at Osaka University, Japan. The image depicts the strong electron affinity of the fluorinated dihydropentalene-1,4-dione (FPD) structure, in which the electron-rich amino groups in the diketopyrrolopyrrole (DPP) skeleton are replaced with a strongly electronegative difluoromethylene unit. Read the full text of the article at 10.

Fluorinated Dihydropentalene-1,4-Dione: A Strong Electron-Accepting Unit with Organic Semiconductor Characteristics.

The development of electron-accepting units is of significant importance because the construction of donor (D)-acceptor (A) configurations is an effective strategy for tuning the electronic properties of π-conjugated systems. Although doubly fused pentagons represented by diketopyrrolopyrrole (DPP) have been used as an effective electron-accepting unit, the relatively high-lying frontier molecular orbital levels (FMOs) leave room for further improvement. We report herein the synthesis of a fluorinated dihydropentalene-1,4-dione (FPD) derivative as a strong electron-accepting unit and the development of D-A-D π-extended molecules.

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.

Synthesis and intramolecular ring transformation of N,N'-dialkylated 2,6,9-triazabicyclo[3.3.1]nonadienes.

The first and facile synthesis of N,N'-dialkylated 2,6,9-triazabicyclo[3.3.1]nonadienes was achieved by the [4 + 4] self-condensation of β-formyl-β-nitroenamine in the presence of ammonium acetate.

Comparison of Substituting Ability of Nitronate versus Enolate for Direct Substitution of a Nitro Group.

α-Nitrocinnamate underwent the conjugate addition of an active methylene compound such as nitroacetate, 1,3-dicarbonyl compound, or α-nitroketone, and the following ring closure afforded functionalized heterocyclic frameworks. The reaction of cinnamate with nitroacetate occurs via nucleophilic substitution of a nitro group by the -attack of the nitronate, which results in isoxazoline -oxide. This protocol was applicable to 1,3-dicarbonyl compounds to afford dihydrofuran derivatives, including those derived from direct substitution of a nitro group caused by -attack of enolate.

Development of a safely handleable synthetic equivalent of cyanonitrile oxide by 1,3-dipolar cycloaddition of nitroacetonitrile.

Dianionic cyano-aci-nitroacetate affords 3-cyanoisoxazol(in)es upon heating with a range of dipolarophiles in the presence of hydrochloric acid. In this reaction, nitroacetonitrile is formed as an intermediate active species, which serves as a synthetic equivalent of cyanonitrile oxide that can participate in a 1,3-dipolar cycloaddition reaction.

Fluorescence Behavior of Bis(cyanostyryl)pyrrole Derivatives Depending on the Substituent Position of Cyano Groups in Solution and in Solid State.

We synthesized a novel fluorophore of distyrylpyrrole derivatives possessing cyano groups at different positions on olefin. Their fluorescence properties in solution and solid state were investigated by photoluminescence quantum yield and lifetime measurements, which provided a radiative decay constant ( k) and nonradiative decay constant ( k). The derivative with cyano groups at the inner position of the molecule, inner isomer, shows a high fluorescence quantum yield (Φ = 0.

Phosphine Induced Dimerization of Propargyl Alcohols Leading to Allyl Propargyl Ethers.

A facile method for synthesizing allyl propargyl ethers (APEs) was developed based on the dimerization of propargyl alcohols. The reaction proceeded via an oxaphosphetane intermediate, which was generated without the use of a strong base, thus making this process a pseudo-Wittig reaction under mild reaction conditions. A wide variety of functional groups, including formyl and pyridyl groups were tolerated, thus yielding the corresponding functionalized APEs, which are otherwise not readily prepared via conventional methods.

Direct dihalo-alkoxylation of nitroalkenes leading to β,β-dihalo-β-nitroethyl alkyl ethers.

A highly efficient one-pot synthesis of β,β-dihalo-β-nitroethyl alkyl ethers is achieved by the treatment of nitroalkenes with alcohols and N-halosuccinimides in the presence of sodium hydride. The notable advantages of this protocol are that it involves simple experimental manipulations and tolerates a wide range of functional groups. Further transformations of the obtained ethers, such as allylation and conversion to β,β-dihalogenated vinyl ethers, are also investigated.

Effects of Alkyl Chain Length and Hydrogen Bonds on the Cooperative Self-Assembly of 2-Thienyl-Type Diarylethenes at a Liquid/Highly Oriented Pyrolytic Graphite (HOPG) Interface.

An appropriate understanding of the process of self-assembly is of critical importance to tailor nanostructured order on 2D surfaces with functional molecules. Photochromic compounds are promising candidates for building blocks of advanced photoresponsive surfaces. To investigate the relationship between molecular structure and the mechanism of ordering formation, 2-thienyl-type diarylethenes with various lengths of alkyl side chains linked through an amide or ester group were synthesized.

Diarylethene Self-Assembled Monolayers: Cocrystallization and Mixing-Induced Cooperativity Highlighted by Scanning Tunneling Microscopy at the Liquid/Solid Interface.

Stimulus control over 2D multicomponent molecular ordering on surfaces is a key technique for realizing advanced materials with stimuli-responsive surface properties. The formation of 2D molecular ordering along with photoisomerization was monitored by scanning tunneling microscopy at the octanoic acid/highly oriented pyrolytic graphite interface for a synthesized amide-containing diarylethene, which underwent photoisomerization between the open- and closed-ring isomers and also a side-reaction to give the annulated isomer. The nucleation (Kn) and elongation (Ke) equilibrium constants were determined by analysis of the concentration dependence of the surface coverage by using a cooperative model at the liquid/solid interface.

Photoinduced Four-State Three-Step Ordering Transformation of Photochromic Terthiophene at a Liquid/Solid Interface Based on Two Principles: Photochromism and Polymorphism.

We have investigated photoinduced ordering transformation of a photochromic terthiophene derivative by scanning tunneling microscopy (STM) at the trichlorobenzene (TCB)/highly oriented pyrolytic graphite (HOPG) interface. The open-ring and annulated isomers of the terthiophene formed two-dimensional molecular orderings with different patterns while the closed-ring isomer did not form any ordering. The ordering of the open-ring isomer exhibited polymorphism depending on the concentration of supernatant solution.

Phototriggered formation and disappearance of surface-confined self-assembly composed of photochromic 2-thienyl-type diarylethene: a cooperative model at the liquid/solid interface.

A photoresponsive self-assembly on a 2-D surface was investigated by scanning tunnelling microscopy (STM). The open-ring isomer of a diarylethene derivative showed an abrupt ordering formation at a critical concentration, which was successfully reproduced by a cooperative model based on Langmuir-type adsorption.