Photochromic guests in organogels

3,3-Diphenyl-9,10-di-n-undecyloxypyrano[3,2-a]phenazine 3 was designed to b e incorporated into fibres of 2,3-di-n-undecyloxyphenazine which display ge l-forming ability in various fluids. A spectrokinetic study and the determi nation of the temperatures of gel-to-sol phase transition, give evidence of the insertion of the photochromic chromene into the organogelator network. Under continuous irradiation, the photochromic reaction induces a decrease of the gel strength which can be used to trigger the gel-to-sol phase tran sition.