A spectroscopic study on the dissociation behavior of 4-hydroxybenzylideneacetone type NLO chromophores in the presence of sodium hydroxide

Interactions of phenolic and carboxylic groups containing NLO chromophores with NaOH in methanol were investigated by UV/vis, fluorescence and 1H NMR measurements. With the aid of a mathematical fitting procedure, it was possible to separate the single contributions of the differently charged chromophore molecules to the overall UV/vis spectra. Individual concentrations of the involved species in dependence on the NaOH concentration were calculated by approximation of measured and calculated UV/vis spectra.The fully deprotonated chromophores with their higher extent of conjugation did not exhibit remarkable fluorescence while the 3rd order NLO activity was observed to show the opposite behavior.