Eugenol and its azo derivatives: an auspicious tool for potential detecting metal cations

Natural products are an essential source for obtaining versatile building blocks for various purposes. Many of these molecules are present in plant extracts and essential oils, which give them interesting physicochemical properties and relevant biological activities. From a chemical point of view, essential oils are synergistic volatile mixtures based essentially on phenolic compounds, terpenes and phenylpropanoids. Phenylpropanoids are an extremely promising class of lead compounds, into which eugenol, the major constituent of clove essential oil, fits perfectly.

Harnessing the potential of secondary metabolites provides an encouraging avenue for diverse research areas. For example, eugenol is a reasonable siderophore, capable of forming complexes with ferrous ions. From this perspective, it is possible to implement structural alterations to the respective molecules through synthetic processes, in order to enhance their ability to form complexes with other metal cations, namely by incorporating functional groups that have donor atoms that facilitate the formation of complexes.

In this way, it was possible to evaluate eugenol's ability to complex with various metal cations, by UV-vis spectroscopy, and to construct a series of azo dyes through the coupling reaction with diazonium salts of different aromatic amines. The new eugenol-based azo dyes as potential colored chelating agents were full characterized by the usual analytical techniques. The UV-vis properties with emphasis in solvent effects were studied and will be discussed.