Water solvent effect on the first hyperpolarizability of p-nitrophenol and p-nitrophenylphosphate: a time-dependent density functional study.
The first hyperpolarizabilities of p-nitrophenol and p-nitrophenylphosphate have been investigated in vacuum and in neutral aqueous solution by means of time-dependent density functional theory. The calculated excited states and hyperpolarizabilities obtained for these systems and for the molecules of phenol, nitrobenzene, and p-nitroaniline in vacuum match well with the experimental trends. The water solvent has been described by the conductorlike screening model and has been completed by water molecules interacting by hydrogen bonds with the solute. The results show a significant effect of the solvent on the first hyperpolarizability. In particular, the hyperpolarizability of p-nitrophenylphosphate (6.78 x 10(-30) esu) in vacuum is only 1.2 times larger than p-nitrophenol (5.63 x 10(-30) esu), whereas it is almost twice higher in aqueous environment, 12.6 x 10(-30) and 6.5 x 10(-30) esu, respectively. This difference in the nonlinear response in neutral water makes the p-nitrophenylphosphate substrate a suitable probe for measuring the activity of alkaline phosphatase enzymes.
Guthmuller
J
J
Laboratoire de Spectrométrie Ionique et Moléculaire (UMR 5579), Université Claude Bernard Lyon 1 and CNRS, 43 Boulevard du 11 novembre 1918, F-69622 Villeurbanne Cedex, France. jguth@lasim.univ-lyon1.fr
Simon
D
D