A photoactivated 'molecular train' for optoelectronic applications: light-stimulated translocation of a beta-cyclodextrin receptor within a stopperedazobenzone-alkyl chain supramolecular monolayer assembly on a Au-electrode

A light-driven molecular shuttle is organized on a gold electrode surface. The assembly consists of a ferrocene-functionalized beta -cyclodextrin, Fc- beta -CD, molecule threaded on a monolayer-immobilized long alkyl component containing a photoisomerizable azobenzene unit, and terminated with a bulk y anthracene group. The Fc-beta -CD resides preferentially on the trans-azo benzene component, and photoisomerization of the trans-azobenzene to the ci s-azobenzene state causes the translocation of the Fc-beta -CD to the alkyl -chain component of the assembly. The state of the molecular shuttle is ele ctronically transduced by chronoamperometry. The interfacial electron trans fer rate constants for the oxidation of the ferrocene units of Fc-beta -CD in the respective positions are k(t) = 65 s(-1) and k(c) = 15 s(-1). The li ght-driven translocation of Fc-beta -CD is reversible, and proceeds by the cyclic isomerization of the azobenzene component between the trans and cis states. (C) 2001 Elsevier Science B.V. All rights reserved.