Because of the presence of the basic amine function in PAT 1 we further investigated the possibility of pH-induced control over aggregation. We expected that protonation of the aggregates would lead to charge repulsion and thus dissolution, while addition of base should be able to reverse this process (Figure ). To our delight addition of three to 10 equivalents of trifluoroacetic acid (TFA) to the aggregated E isomer of PAT 1 in toluene/CH3CN