Vinylazulenes chromophores: Synthesis and characterization

• 14 compounds containing a vinylazulene moiety and a heterocycle were prepared.
• Information about chemical shifts of relevant protons was compiled.
• The UV–vis spectra were detailed and correlated with the structure of compounds.
• Solvatochromism and the existence of isosbestic point were investigated.
• Redox potentials of the compounds were discussed in agreement with their structure.

Several vinylazulenes containing heterocyclic units were prepared using Knoevenagel condensation. The condensation took place between electron rich 1-azulenecarbaldehyde derivatives and their vinylogues with heterocycles. The catalysts were chosen in order to catalyze the reaction without giving side reactions, such as heterocycle decomposition or formylazulene decarbonylation. Several NMR signals were briefly discussed. The optical properties of the colored substances were evidenced as a function of their structure. The pH-dependence of the chromophores was evidenced for two compounds; as well as their active solvatochromism. Their electrochemical properties were evaluated from the redox potentials and correlated to their structure.

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