Azulene Moiety as Electron Reservoir in Positively Charged Systems; A Short Survey

The non-alternant aromatic azulene, an isomer of alternant naphthalene, differs from the latter in peculiar properties. The large polarization of the pi-electron system over the seven and five rings gives to azulene electrophile property a pronounced tendency to donate electrons to an acceptor, substituted at azulene 1 position. This paper presents cases in which azulene transfers electrons to a suitable acceptor as methylium ions, positive charged heteroaromatics and examples of neutral molecules that can accept electrons. The proposed product synthesis was outlined and the expected electron transfer was highlighted by analyzing the NMR, UV-Vis spectra and the pK(R)(+) values.

Automated summary

This paper explores the unique properties of non-alternant aromatic azulene compared to alternant naphthalene, focusing on its electron transfer capabilities to various acceptors. The proposed product synthesis and expected electron transfer are highlighted through the analysis of NMR, UV-Vis spectra, and pK(R)(+) values.