Synthesis of Ring-Fused Pyridinium Salts by Intramolecular Nucleophilic Aromatic Substitution Reaction and Their Optoelectronic Properties

Abstract

The synthesis of nitrogen cation-doped polycyclic aromatic hydrocarbons (PAHs) having a variety of counteranions is reported via the trimethylsilyl (TMS)-promoted intramolecular aromatic nucleophilic substitution (SAr) reaction of fluoroarenes and pyridine groups. The electrochemical properties and optical properties of the obtained nitrogen cation-doped PAHs were studied in detail, clarifying that they have low-lying LUMO levels and good emission properties derived from the incorporation of planar N-arylpyridinium moieties.

Synthesis of a conjugated polymer with ring-fused pyridinium units via a postpolymerization intramolecular cyclization reaction

“…As a summary of the properties of 2e-g, the solubility and melting points of the products changed due to the differences in the characteristics of the anion parts, whereas there were no significant differences in electrochemistry, absorption and emission spectra among 2e-g and previously reported 2a [17]. These results suggest that the anions incorporated in this study rarely affect the electronic structures of either the ground state or the excited states.…”

“…3a, b, Table S6). The calculated lowest unoccupied molecular orbital (LUMO) of P2e was −4.05 eV, which was lower than those of 2e (−3.77 eV) and 4a (−3.87 eV) [17].…”

“…The soluble brown powder P2e was then analyzed by 1 H and 19 F NMR. Overlaid 1 H and 19 F NMR spectra of P2e, 4d [17], 2g, P1, 3 [17] and 1 are shown in Fig. 2.…”

“…Previously, we reported an intramolecular nucleophilic aromatic substitution (S N Ar) reaction to construct fused aromatic molecules containing an N-aryl pyridinium motif ( Fig. 1) [17]. In that study, precursor molecules (1 and 3) were synthesized by linking phenylpyridine and perfluoroarene, followed by intramolecular S N Ar, resulting in the construction of fused pyridinium motifs (2 and 4).…”

“…For the cyclization reaction of 1 and 3, the use of TMS-X (TMS = trimethylsilyl, X = TfO − , Cl − , Br − , I − ) was found to effectively promote the reaction to give 2 and 4 by scavenging the liberated fluoride ion upon S N Ar reaction. The cyclization of 1 without any additive resulted in the decomposition of the product [17].…”