Photochromic Hydrazone Switches with Extremely Long Thermal Half-Lives

A family of easily accessible light-activated hydrazone switches
has been developed having thermal half-lives of up to 2700 years!
Structure–property analysis shows that replacing the rotor
pyridyl group of our typical hydrazone switch with a phenyl one leads
to the long-lived negative photochromic compounds. The switching properties
of the hydrazones in both toluene and DMSO were assessed offering
insights into the kinetics and thermodynamics of the switching process.