Novel photochromic molecules based on 4,5-dithienyl thiazole with fast thermal bleaching rate

Novel photochromic triangle terarylenes are synthesized, and their photochromic properties and thermal bleaching kinetics are investigated. Fairly high photochemical coloration reactivity is observed with photochemical quantum yield as high as 0.6 for 4,5-dithienyl thiazole derivative. Introduction of phenyl-ethynyl groups into the molecular structure allows systematic control of thermal cycloreversion time constant over 10(5) times, and the half-lifetime shorter than 2 s is achieved at 303 K. The kinetic analysis of thermal cycloreversion reaction clearly shows significant contribution of frequency factor A. A novel molecular designing concept for systematic control of thermal bleaching reaction rate is presented without taking bulky functional groups on reaction center.