Synthesis and Electronic Properties of Length-Defined 9,10-Anthrylene–Butadiynylene Oligomers

Linear π-conjugated oligomers consisting of anthracene and diacetylene units were readily synthesized by a one-pot process that involved desilylation and oxidative coupling from appropriate building units. We were able to isolate length-defined oligomers ranging from 2-mer to 6-mer as stable and soluble solids. The bathochromic shifts in the UV–vis spectra suggested that the π-conjugation was extended with elongation of the linear chain. Cyclic voltammetric measurements showed characteristic reversible oxidation waves that were dependent on the number of anthracene units

Synthesis and Electronic Properties of Length-Defined 9,10-Anthrylene–Butadiynylene Oligomers

Linear π-conjugated oligomers consisting of anthracene and diacetylene units were readily synthesized by a one-pot process that involved desilylation and oxidative coupling from appropriate building units. We were able to isolate length-defined oligomers ranging from 2-mer to 6-mer as stable and soluble solids. The bathochromic shifts in the UV–vis spectra suggested that the π-conjugation was extended with elongation of the linear chain. Cyclic voltammetric measurements showed characteristic reversible oxidation waves that were dependent on the number of anthracene units

Isolable Triradical Trication of Hexaaza[1₆]paracyclophane with Embedded 9,10-Anthrylenes: A Frustrated Three-Spin System

A new derivative of hexaaza­[1₆]­paracyclophane in which <i>p</i>-phenylenes are alternately replaced by 9,10-anthrylenes was prepared to investigate the impact on overall π-conjugation as well as conformational change of the macrocycle. The charge and spin distribution for one-electron and three-electron oxidation of the macrocycle was elucidated by means of electrochemical, spectroelectrochemical, EPR spectroscopic, and SQUID magnetometric methods. In particular, the triradical trication was successfully isolated as an air-stable salt, and moreover, its structure was disclosed by X-ray analysis. The triradical trication was characterized as a spin-frustrated three-spin system with the antiferromagnetic exchange interaction (<i>J</i>/<i>k</i>_B ≃ – 74 K)

Synthesis of 1,2-Bis(2-aryl‑1<i>H</i>‑indol-3-yl)ethynes via 5-<i>exo</i>-Digonal Double Cyclization Reactions of 1,4-Bis(2-isocyanophenyl)buta-1,3-diyne with Aryl Grignard Reagents

New π-conjugated 1,2-bis­(2-aryl-1<i>H</i>-indol-3-yl)­ethynes <b>1a</b>–<b>j</b> having various substituents on the two aryl groups were efficiently synthesized via unusual 5-<i>exo</i>-digonal double isocyanide-acetylene cyclization reactions of 1,4-bis­(2-isocyanophenyl)­buta-1,3-diyne <b>3</b> and aryl Grignard reagents (R-MgBr, R = C₆H₅ (<b>1a</b>), 4-H₃CC₆H₄ (<b>1b</b>), 2-H₃CC₆H₄ (<b>1c</b>), 3-MeOC₆H₄ (<b>1d</b>), 3-(CH₃)₂NC₆H₄ (<b>1e</b>), 4-F₃CC₆H₄ (<b>1f</b>), 4-FC₆H₄ (<b>1g</b>), 3-FC₆H₄ (<b>1h</b>), 4-PhOC₆H₄ (<b>1i</b>), and 2-Naph (<b>1j</b>)) in 19–85% yields. The UV–vis spectra were rationalized in detail using time-dependent DFT and single point calculations. The fluorescence emission peaks for <b>1a</b>–<b>j</b> were observed at around 450 nm. Especially for <b>1f</b> and <b>1j</b>, those spectra displayed broad emission bands and relatively large Stokes shifts (3977–4503 cm^–1), indicating the contribution of an intramolecular charge transfer. The absolute quantum yields (0.50–0.62) of <b>1a</b>–<b>j</b> were higher than those of parent <b>8</b> (0.19) and 2-phenyl-1<i>H</i>-indole (0.11). The electrochemical features for <b>1a</b>–<b>j</b> were investigated by cyclic voltammetry. The frontier molecular orbital levels for <b>1a</b>–<b>j</b> were estimated based on the combination of oxidation potentials, UV–vis, and DFT calculated data. The structural property of 1,2-bis­(2-phenyl-1<i>H</i>-indol-3-yl)­ethyne <b>1a</b> was characterized by several spectroscopic methods and finally determined by X-ray analysis of a single crystal of <b>1a</b> recrystallized from ethyl acetate. The structural features of <b>1a</b>–<b>j</b> were also supported by DFT calculations