N14 quadrupole coupling in some thermochromic and photochromic n-salicylideneanilines

In order to throw some light on the nature of the O-H--N hydrogen bond and on the mechanism responsible for thermochromism and photochromism in some solid N-salicylideneanilines, we determined by proton-nitrogen double resonance the N¹⁴ quadrupole coupling tensors of thermochromic salicylidene-3-chloroaniline, photochromic salicylidene-2-chloroaniline and of thermochromic 5′-chloro-salicylidene-aniline.