Ab initio investigation on the second-order nonlinear optical responses in keto-enol equilibria of salicylideneanilines.
The keto-enol (K-E) tautomerization equilibrium, more precisely, the keto-amine/enol-imine equilibrium, has been investigated for a series of substituted salicylideneanilines in view of designing compounds with a contrast of second-order nonlinear optical properties. Substituting the salicylidene ring by an acceptor group or the other ring by a donor prevents the K form from being stable, whereas in the other cases, the K form can easily be converted to the E form due to the small activation barrier, figuring out in most cases that the K form is metastable. For a representative set of donor/acceptor substituents, the E and K forms present a sufficiently large contrast of beta to allow its detection by using electric-field-induced second harmonic generation or hyper-Rayleigh scattering. The largest beta values are mainly associated with species bearing a donor in the para position of the salicylidene ring and an acceptor on the other ring whereas the largest beta values are generally found for the E form.
Guillaume
Maxime
M
Laboratoire de Chimie Théorique Appliquée, Facultés Universitaires Notre-Dame de la Paix (FUNDP), rue de Bruxelles 61, B-5000 Namur, Belgium.
Champagne
Benoît
B
Markova
Nadezhda
N
Enchev
Venelin
V
Castet
Frédéric
F
D000814:Aniline Compounds / Q000737:chemistry*; D002627:Chemistry, Physical / Q000379:methods; D008956:Models, Chemical; D015233:Models, Statistical; D008968:Molecular Conformation; D015394:Molecular Structure; D055095:Optics and Photonics; D012545:Schiff Bases / Q000737:chemistry*; D012984:Software; D013696:Temperature; D013816:Thermodynamics