Synthesis and Electrochemical Properties of Azulene-Substituted Tetracyanobutadiene and Dicyanoquinodimethane Chromophores Connected with Naphthalene Cores

Abstract

Azulene-substituted tetracyanobutadienes (AzTCBDs) and dicyanoquinodimethanes (AzDCNQs) connected with naphthalene cores were prepared by the reaction of 1-azulenylalkynes with tetracyanoethylene (TCNE) and 7,7,8,8-tetracyanoquinodimethane (TCNQ) in a formal [2 + 2] cycloaddition-retroelectrocyclization. The characteristic intramolecular charge transfer (ICT) characters were investigated by using UV/Vis spectroscopy and theoretical calculation. The redox behaviors of AzTCBDs and AzDCNQs were examined by cyclic voltammetry and differential pulse voltammetry, which revealed their properties of multi-electron transfer depending on the number of AzTCBD and AzDCNQ moieties. Moreover, significant color changes were observed by visible spectroscopy under the electrochemical reduction conditions.

Azulene‐Based Donor–Acceptor Systems: Synthesis, Optical, and Electrochemical Properties

“…UV/Vis of 1-AzTCBDs 29 and 30 with naphthalenec ores ( Figure 5) showed broad absorption bands at around 400-700 nm, arising from the ICT betweent he azulenea nd TCBD units. [48] Likewise, bis-1-AzTCBDs 31-34 also displayed broad absorption bands in the visible region, without ac lear peak maximai nt he region. Similart ot he bis-1-AzTCBDs 23-28,t he extinction coefficients of bis-1-AzTCBDs 31-34 increased in comparison to those of 1-AzTCBDs 29 and 30 as the number of 1-AzTCBD units on naphthalene ring increased.…”

“…[46] They also revealed their redox behaviors, which weren ot influenced by the number of TCBDu nits on the corannulene core. [48] Likewise, bis-1-AzTCBDs 31-34 also displayed broad absorption bands in the visible region, without ac lear peak maximai nt he region. [47] However,t he influence of the number and substitution positiono ft he TCBD units on pyrene on the spectroscopic and electrochemical properties were not investigated.…”

“…UV/Vis of 1‐AzTCBDs 29 and 30 with naphthalene cores (Figure ) showed broad absorption bands at around 400–700 nm, arising from the ICT between the azulene and TCBD units . Likewise, bis‐1‐AzTCBDs 31 – 34 also displayed broad absorption bands in the visible region, without a clear peak maxima in the region.…”

Alkynylazulenes as Building Blocks for Highly Unsaturated Scaffolds

“…and other research groups reported the synthesis of arylethynylazulenes 91 – 96 in 37–99% yield by Pd‐catalyzed cross coupling of the appropriate ethynylazulene with haloarenes or the inverse cross coupling reaction of the appropriate haloazulene with the corresponding ethynylbenzenes (Figure 14). [23,25,26,60–66] …”

“…Bis(1‐azulenyl)naphthalene derivatives 138 – 141 [65] were also synthesized by Pd‐catalyzed alkynylation of iodoazulene 98 b with the corresponding diethynylnaphthalenes 137 (Scheme 30). [85] …”