Dithienylethene Proton Cranes - Another Way to Switch the Tautomeric State

Dithienylethenes (DTE) are a rare class of photoswitches, which are capable of undergoing a fast photochemical cyclization leading to increased aromaticity of the closed isomer. At the same time in most of the tautomeric compounds the tautomeric state is strongly affected by the change in the aromaticity of the involved aromatic rings. Very recently it has been shown that the implementation of DTE moiety in salicylideneaniline leads to switching of the stable open form enol tautomer to thermodynamically stable keto tautomer upon cyclization. In the present communication we consider in depth, by using DFT and TD-DFT methodology, the reasons for low efficiency of these new switches and further develop the idea for DTE based switching in proton cranes.