Abstract Symmetric pyrene-linked bis-salicylidene Schiff-base NBPP bears dual phenolic-imine intramolecular hydrogen bonds. DFT and TD-DFT computations were performed to decode its excited-state intramolecular proton-transfer (ESIPT) behaviours across cyclohexane, chloroform and acetonitrile. Geometric parameters, simulated IR spectra, QTAIM-BCP and ELF-CVB analyses consistently confirm that elevated solvent polarity strengthens excited-state hydrogen-bond interactions.
