Polarisation charge switching through the motion of metal atoms trapped in fullerene cages

Abstract

The formation of an endohedral fullerene can lead to charge transfer and the generation of a trapped positively charged metal ion. Using Ca@C₆₀ and [Ca@C₆₀]⁺ endohedral fullerenes as models, density functional theory calculations predict that the motion of a calcium ion within a fullerene is accompanied by large changes in electron density on the surrounding carbon cage. In the case of [Ca@C₆₀]⁺, partial atomic charge distribution on the carbon cage is split between hemispheres into regions of positive and negative charge as Caⁿ⁺ moves inside the fullerene cage (non-integer n strongly depends on position of the ion). It is proposed that within tethered fullerene cages the movement of partial atomic charge could form the bases of a molecular polarisation storage bit, and that adopted in the form of [Ca@C₆₀]⁺ the presence of an overall charge may offer a route to either optical or electronic control.