Anionic clay surface facilitates electron transfer between an excited donor encapsulated within a cationic capsule and a cationic electron acceptor

Abstract

Fluorescence quenching of an excited guest encapsulated within a cationic host by a cationic molecule was examined on an anionic inorganic surface. Repulsion between the host and the quencher was overcome by adsorbing both an anionic surface. Dimethyl stilbene (DMS), octa amine (OAm₂¹⁶⁺), viologen derivatives (VD²⁺) and saponite are used as guest, cationic capsule, cationic electron acceptor and anionic inorganic surface, respectively. The fluorescence behavior of DMS within OAm₂¹⁶⁺ (denoted as DMS@OAm₂¹⁶⁺) was observed by steady-state and time-resolved fluorescence measurements. As a result of electron transfer the fluorescence of DMS@OAm₂¹⁶⁺ was quenched by VD²⁺ under the presence of saponite, while no quenching was observed in the absence of saponite. Those results indicate that the dynamic electron transfer between DMS@OAm₂¹⁶⁺ and VD²⁺ which are electrostatically repulsive, can be observed in the (DMS@OAm₂¹⁶⁺)-VD²⁺-saponite triad supramolecular system where the two cationic systems are brought closer by the anionic clay sheet.