Aggregate dependent electrochromic properties of amino acid appended naphthalene diimides in water

Naphthalene diimides can have electrochromic applications due to their highly stable dark reduced state along with a transparent colourless neutral state. We show here that the colouration and reversibility of water-dispersible amino acid appended NDIs are directly influenced by the aggregated state present at different pH using spectroelectrochemistry, small angle neutron scattering (SANS) and cyclic voltammetry (CV). We find the aggregation itself is influenced by both pH and the amino acid or dipeptide in the structure, with each NDI having a preferred morphology giving rise to a more intensely coloured state.