Synthesis and Two-Electron Redox Behavior of Diazuleno[2,1-a:1,2-c]naphthalenes

Abstract

The Diels-Alder reaction of di-2-azulenylacetylene with tetraphenylcyclopentadienone afforded 7,8,9,10-tetraphenyldiazuleno[2,1-a:1,2-c]naphthalene in one pot via autoxidation of the presumed 1,2-di-2-azulenylbenzene derivative. In contrast, a similar reaction of bis(1-methoxycarbonyl-2-azulenyl)acetylene with tetraphenylcyclopentadienone gave the 1,2-di-2-azulenylbenzene derivative. The following cyclodehydrogenation reaction of the benzene derivative with iron(III) chloride afforded diazuleno[2,1-a:1,2-c]naphthalene 6,11-bismethoxycarbonyl derivative. The redox behavior of these novel diazuleno[2,1-a:1,2-c]naphthalenes was examined by cyclic voltammetry (CV). These compounds exhibited two-step oxidation waves at +0.22 to +0.71 V upon CV, which revealed the formation of a radical cation and dication stabilized by the fused two azulene rings under the electrochemical oxidation conditions. Since the 1,2-di-2-azulenylbenzene derivative was oxidized at higher oxidation potentials (+0.83 and +1.86 V), the fusion of the two azulene rings to naphthalene increased electron-donating properties because of the formation of a closed-shell dicationic structure. Formation of the radical cation was characterized by UV-vis spectroscopy under the electrochemical oxidation conditions, although no evidence was obtained for the presumed dication under the conditions of the UV-vis spectroscopy measurement.

Universality of Molten State of Alkyl Chain in Liquid-Crystalline Mesophases: Smectic E Phase of 6-Alkyl-2-phenylazulene

“…The socalled "mosaic pattern" is recognized. Similar textures were observed also for other compounds including 8PA, 5,7 in which the mesophase has been identified as SmE phase. Figure 6 shows results of wide-angle X-ray diffraction of nPA (n = 410) in the mesophase.…”

“…5,9 Samples were seemingly blue powder, but crystallite in reality. In most experiments described below, the samples at the beginning were basically in this "powder" form.…”

“…The present authors reported that two members (n = 8 and 16) of 6-alkyl-2-phenylazulene (nPA, n being the number of carbon atoms in the alkyl group as show in Figure 1b) have SmE phase as a mesophase. 5,6 The comparison of their properties suggested possible difference between nPA and nTCB.…”

Synthesis of donor–acceptor chromophores by the [2 + 2] cycloaddition of arylethynyl-2H-cyclohepta[b]furan-2-ones with 7,7,8,8-tetracyanoquinodimethane

“…6,11 Thus, the reaction of 1 with TCNQ in refluxing ethyl acetate afforded 10 in 91% yield as a sole product (Scheme 1). Proposed reaction 20 sequence is also shown in Scheme 1. The reaction commences with the formal [2+2] cycloaddition between the exocyclic C=C double bond of TCNQ and the alkyne moiety of 1, followed by the ring opening of the intermediately formed-strained cyclobutene derivative to give 10 as shown in the parentheses.…”

“…Cyano-based acceptor is one of the most 20 promising units for the application to the organic electronic devices within a large number of organic acceptors previously reported.…”