ChemInform Abstract: Photochromic Dihetarylethenes. Part 5. Synthesis, Structure, and Photochromic Properties of 4,4′‐Disubstituted 1,2‐Bis[2‐ethyl‐5‐ethylthio(ethylsulfonyl)‐3‐thienyl] perfluorocyclopentenes.

Abstract

A series of new photochromic compounds were obtained tbr the first t+me from 1,2-his(2-ethy]thio-3-thienyl)perfluorocyctopentene by substi~ttting bromine atoms or carboxy. alkoxycarbonyt, and carbamoyl groups for hydrogen atoms m positions 4 and 4'. Introduction of these sub~tituent'~ causes a slight bathochromic shift [b~. 20--30 nm) of a long-wavelength :~bsorption band R~ the cyclic form and significantly increases the quantum yields of photocycfization tD A.,B and ring opening ~bs~, ,. Depending on Ihe nature of a substituent. d~.~..+t ~ decreases in the. order COOH > COOMe > CONHAr. The quantum yields are markedly reduced when the cthylthio groups in posinons 5 and 5" are replaced hy eth,dsultbnu groups (a tenfold reduction in 4~a.,B and a tbur-to fiveibtd reduction m %a-,.x)-The most considerable bathochromic shift of a long-wavelength band and the highest quantum yields of totward and reverse photoreacfions were obsewed for 1,2-bist4-bromo-2-ethyl-5-ethyhi~io-3-thienyl)perllunrocyclopentenc. 1, perfluorocyclopemene was qruclurafly characterized b.v X-ray diffraction analysis.