Having largely understood the NaphPO4 / NaphAcPO4 reaction cycle, we sought to explore functional aspects of chemically-driven acylphosphate steady states. For this reason, we turned our attention to the transient acylation of pyrene-1-phosphate (PyrPO4). The extended π-system in PyrPO4 leads to increased lipophilicity and stronger intermolecular (i.e., π-π) interactions such that the charge reduction during anhydride and/or carbodiimide fueled acetylation results in transient aggregation and phase separation of the respective product (Figure and S9, Video S1 and S2). The system could successfully be refueled for four times by the consecutive addition of four equivalents of fuel. Compared to NaphAcPO4, which would hydrolyze within minutes under the standard conditions applied here (Figure ), it is remarkable that the turbidity caused by pyrene-1-acetylphosphate (PyrAcPO4) lasts for several hours, which could be indicative of aggregation induced negative feedback and exemplifies the utility of acylphosphate for fueled self-assemblies. Because chemically-driven self-assemblies are increasingly well-established and only few examples have been reported on transient changes in optical properties, we decided to pursue unique opportunities that pyrenes such as PyrPO4 present in the latter arena. By employing the reaction cycle depicted in Figure , we were able to establish chemically-driven excimer emission. PyrPO4 and adipic acid were used as substrates in mixed aqueous solvent (H2O/DMF 1:1) and EDC was added as a fuel to facilitate the two-fold phosphorylation of the diacid. The resulting product Pyr2AcP possesses two covalently linked pyrene moieties and displays a red-shifted fluorescence compared to the respective monomer emission. The origin of this spectral shift can be attributed to the formation of excimers, i.e. the intramolecular interaction between two pyrene moieties.