Synthesis of 2‑Azulenyltetrathiafulvalenes by Palladium-Catalyzed Direct Arylation of 2‑Chloroazulenes with Tetrathiafulvalene and Their Optical and Electrochemical Properties

Tetrathiafulvalene (TTF) derivatives with 2-azulenyl substituents <b>5</b>–<b>11</b> were prepared by the palladium-catalyzed direct arylation reaction of 2-chloroazulenes with TTF in good yield. Photophysical properties of these compounds were investigated by UV–vis spectroscopy and theoretical calculations. Redox behavior of the novel azulene-substituted TTFs was examined by using cyclic voltammetry and differential pulse voltammetry, which revealed their multistep electrochemical oxidation and/or reduction properties. Moreover, these TTF derivatives showed significant spectral change in the visible region under the redox conditions

Preparation of a Cyclic Polyphenylene Array for a Zigzag-Type Carbon Nanotube Segment

Preparation of cyclic polyphenylene array <b>2</b>, which corresponds to a complete carbon array of a zigzag-type CNT segment with (18,0)-structure, has been established by a Diels–Alder reaction of cyclic biphenylylene–acetylene derivative <b>1</b> with tetraphenylcyclopentadienone. The reaction of <b>2</b> with excess FeCl₃ realized a presumed cyclodehydrogenation reaction and elimination of the alkyl chains that were introduced as a measure to counter the low solubility problem, but this resulted in the formation of a complicated mixture that included the mass region of a presumed zigzag-type CNT segment with (18,0)-structure. The rather efficient blue emission of cyclic compounds <b>1</b> and <b>2</b> was discussed utilizing fluorescence (FL) quantum efficiencies (Φ_FL) and lifetimes (τ_FL) in their crystalline state along with those in dichloromethane solution. Thermal analyses of these compounds revealed their characteristic phase transition behavior. The synthesis of a novel cyclic polyphenylene array by utilizing a Diels–Alder reaction of cyclic phenylene–acetylene compounds with tetraphenylcyclopentadienone should afford an attractive pathway to a novel belt-shaped CNT segment

Synthesis, Properties, and Redox Behavior of Tetracyanobutadiene and Dicyanoquinodimethane Chromophores Bearing Two Azulenyl Substituents

Acetylene derivatives with an azulenyl group at both terminals have been prepared by palladium-catalyzed alkynylation under Sonogashira–Hagihara conditions. These alkynes reacted with tetracyanoethylene and 7,7,8,8-tetracyanoquinodimethane in a formal [2 + 2] cycloaddition–retroelectrocyclization reaction to afford the corresponding new tetracyanobutadienes (TCBDs) and dicyanoquinodimethanes (DCNQs), respectively, in excellent yields. Intramolecular CT absorption bands were found in the UV–vis spectra of the novel chromophores, and CV and DPV showed that they exhibited a reversible two-stage reduction wave, due to the electrochemical reduction of TCBD and DCNQ moieties. Color changes were also observed during the electrochemical reduction

Synthesis of 2‑Methyl-1-azulenyl Tetracyanobutadienes and Dicyanoquinodimethanes: Substituent Effect of 2‑Methyl Moiety on the Azulene Ring toward the Optical and Electrochemical Properties

We describe the comparative study of optical and electrochemical properties of tetracyanobutadienes (TCBDs) and dicyanoquinodimethanes (DCNQs) with a 2-methyl-1-azulenyl group and their derivatives with a 1-azulenyl substituent examined under the same conditions. TCBDs and DCNQs with a 2-methyl-1-azulenyl substituent have been prepared by the Sonogashira–Hagihara alkynylation of the 2-methyl-1-iodoazulene with arylalkyne derivatives, followed by the formal [2+2] cycloaddition–retroelectrocyclization (CA–RE) reaction with tetracyanoethylene and 7,7,8,8-tetracyanoquinodimethane. The optical properties of the TCBDs and DCNQs with a 2-methyl-1-azulenyl group were investigated through the comparison with those of TCBDs and DCNQs with a 1-azulenyl substituent by employing the UV/vis spectroscopy and theoretical calculations. The electrochemical properties of the TCBD and DCNQ derivatives were also examined by cyclic voltammetry and differential pulse voltammetry experiments, which elucidated their multistep redox properties. Furthermore, noticeable spectral changes of these chromophores were identified by the spectroelectrochemical measurements