Naphtyl- and pyrenyl-flavylium dyads: Synthesis, DFT and optical properties

Abstract A one-step preparation of flavylium salts containing naphtyl and pyrenyl moieties is described hereafter. Flavylium salts were successfully characterized by 1 H NMR spectroscopy and ESI-MS spectrometry. Theoretical calculations were carried out by means of Density Functional Theory in order to simulate flavylium cation electronic transitions. Molecular simulation of -naphtyl derivatives displayed a coplanar conformation between naphthalene and benzopyrylium moieties. In contrast, DFT analysis exhibited a non-coplanar arrangement of pyrene and benzopyrylium units. These former statements in coherence with the absorption experiments where the naphtyl-flavylium dyads shows a red-shifted maximum absorption band with respect to pyrene dyads, led us to conclude that these bathochromic effects are associated with a more planar conformation.