First thermal studies on visible-light-switchable negative T-type photochromes of a nitrile-rich series.

Representatives of visible-light-switchable nitrile-rich negative T-type photochromes (NRP) were synthesized. The temperature effect on the thermal relaxation of the photoinduced form of NRP was studied for the first time. It was found that regardless the temperature the reverse thermal reaction in ethanol and 1,4-dioxane proceeded according to a first-order kinetic equation, while an unusual pseudo-zero order of the dark reaction was observed in acetonitrile.