One-Step Synthesis of Novel Flavylium Salts Containing Alkyl Side Chains in Their 3-, 4′-, 5- or 6-Positions and Their Photophysical Properties in Micellar Media

A one‐step preparation of several flavylium salts containing alkyl side chains in their 3‐, 4′‐, 5‐ or 6‐positions is described. Flavylium salts with alkyl side chains in positions 3 or 4′ were isolated from reactions between 2,4‐dihydroxybenzaldehyde and decanophenone, dodecanophenone and 4′‐hexyl‐ or 4′‐dodecylacetophenone. Flavylium salts with alkyl side chains in positions 5 or 6 were prepared through reactions between benzoylacetone and 4‐hexyl‐, 4‐dodecyl‐ or 5‐pentylresorcinol. The new compounds are insoluble or sparingly soluble in water, but readily incorporate into aqueous dispersions of anionic (SDS), cationic (CTAB) or neutral (C12E10) surfactants above their critical micellar concentrations. They also present interesting spectroscopic properties − namely, ultra‐fast proton transfer in the excited state − and the 4′ derivatives also exhibit photochromic behaviour, which might have several applications in the field of self‐assembled systems. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004)