A low molecular weight ESIPT-based probe was synthesized and tested for detecting pH, cations, and anions in aqueous solutions. The probe exhibited a good emission in water due to aggregation induced by π-π* stacking. It gave an “off–on” fluorescent response to higher pHs because of blocking the non-radiative ESIPT after deprotonating phenolic hydroxyl groups. Moreover, the fluorescence emission of the probe (water/ethanol = 3:1, pH 10) was quenched only by Cu²⁺ with limit of detection LOD = 3.2 μM. The stoichiometric ratio of the probe/Cu²⁺ complex was found to be 1:1. Furthermore, changes of the probe’s absorption and emission signals (as outputs) in response to the presence of H⁺ and HO^– or Cu²⁺ and Br⁻ stimuli (as chemical inputs) mimics INHIBIT, IMPLICATION and NOT TRANSFER logic gates.