ELECTRONIC-SPECTRA AND INTRAMOLECULAR HYDROGEN-BONDING OF N, N'-DI-SALICYLOYL-1,2-ETHANEDIAMINE

Absorption, fluorescence and excitation spectra of four dissociation forms (anion, molecule, cation and dication) of N,N'-di-salicyloyl-1,2-ethanediamine (NDSED) in aqueous solution at 295 K and 77 K were examined. The corresponding acid-base equilibrium constants were determined spectrophotometrically in the ground state, and calculated by Forster's cycle in the first excited singlet state. The dual emission (365 and 435 nm) from molecular species by the model of two ground-state rotamer one of them having intramolecular hydrogen bond. Excitation of the "closed-ring" conformer leads to intramolecular proton transfer across the preexisting H bond to give the excited zwitterion, responsible for the long-wavelength emission (435 nm).