Photoinduced refractive-index change in 4-tert-butylcalix[8]arenes bearing N-acyloxyphenylamide chromophores

A study was conducted to demonstrate photoinduced refractive-index change in 4-tert-butylcalix[8]arenes bearing N-acyloxyphenylamide chromophores. O-alkylation of 4-tert-butylcalix[8]arene with ethyl bromoacetate in dry 1-methyl-2-pyrrolidone followed by alkaline hydrolysis of the resulting ester derivative in aqueous ethanol yielded the corresponding carboxylic acid. The reaction of the acid derivative with thionyl chloride resulted in a highly reactive acid chloride, which was coupled with 4-benzyloxyaniline in dry N,N-dimethylformamide (DMF) to produce the amide conjugate. Catalytic debenzylation of this conjugate in tetrahydrofuran (THF) followed by the acylation of the deprotected phenolic hydroxyl group formed 4-tert-butylcalix[8] arenes 1c and 1d substituted with eight 4-acyloxyanilinocarbonyl chromophores. A large change in the refractive index of the calixarene 1c film was also observed when it was irradiated for 60 minutes by 254-nm UV light.