Effect of deprotonation on the spectral and luminescent properties of N,N'-bis(2-hydroxy-4-methylbenzylidene)-N-(2-aminoethyl)ethane-1,2-diamine in ethanol

The absorption and fluorescence spectra of the aromatic azomethine of the N$_3$O$_2$ type – N,N'-bis(2-hydroxy-4-methylbenzylidene)-N-(2-aminoethyl)ethane-1,2-diamine – were studied in ethanol solutions at 293 K. The adding of potassium hydroxide into alcoholic solutions leads to the deprotonation of azomethine and its transition to the anionic form. The time of establishing equilibrium is determined by the ratio of the concentrations of azomethine and alkali. Deprotonation causes significant changes in the spectral and luminescent properties of azomethine, including an increase in the quantum yield of fluorescence by up to 10 times.