Protonation and solvent-interaction effects on the first hyperpolarizability of 2-amino-5-nitropyridine

The protonation effect on the first hyperpolarizability β of 2-amino-5-nitropyridine (2A5NP) is examined by Hyper-Rayleigh Scattering (HRS). Using the HRS technique, the β value of the protonated 2A5NP in acetone is determined to be 22.5 × 10^-30 esu, small in comparison to the value for the neutral form. The measurement is repeated in 1,4-dioxane and methanol solutions to examine the influence of the solvent on β. β depends on the reaction field, which is written as a function of the dielectric constant of the solvent, the variation of β in methanol is inconsistent. From this, it is deduced that the first hyperpolarizability of 2A5NP decreases more significantly by hydrogen bond solvent interactions than by protonation.