Micelle effect on the ‘write–lock–read–unlock–erase’ cycle of 4′-hydroxyflavylium ion

Abstract

In aqueous solution the 4′-hydroxyflavylium ion (AH ⁺ ) can be interconverted into several different neutral forms by light excitation and/or pH changes. All the observed processes are fully reversible and accompanied by strong changes in absorption and emission spectra. This system exhibits properties required by optical memory devices with multiple storage in two different memory levels and non-destructive readout capacity through a write-lock-read-unlock-erase cycle. The effect of micelles on the pH and light induced interconversion of AH ⁺ and its neutral forms has been investigated. Negatively charged sodium dodecyl sulfate micelles stabilize AH ⁺ , whereas the positively charged cetyltrimethylammonium bromide and neutral polyoxyethylene(10) isooctyl phenyl ether (Triton X-100) micelles stabilize the uncharged (basic) forms. Besides affecting the molar fraction distribution of the various species, the presence of micelles also influences their interconversion rates. Addition of micelles can therefore be considered as a third external stimulus (besides light excitation and pH jump) capable of changing the state of this multistate/multifunctional molecular-level system. Particularly interesting is the possibility to change the autolock pH of the photochromic reaction by addition of micelles.