Introduction of ferrocene-containing [2]rotaxanes onto siloxane, silsesquioxane and polysiloxanes via click chemistry

Abstract

The reaction of N₃(CH₂)₃Si(OTMS)₃ (TMS = SiMe₃) with a dialkylammonium having hexynyl group 1, [FcCH₂NH₂CH₂C₆H₄-4-O(CH₂)₄CCH]PF₆ (Fc = Fe(C₅H₄)(C₅H₅)), in the presence of dibenzo[24]crown-8-ether (DB24C8) and [Cu{Fe(CN)₄}]PF₆ catalyst yielded the [2]rotaxane containing the dialkylammonium unit terminated by a bulky silyl group. Azides with a silsesquioxane group react similarly to form the corresponding [2]rotaxanes having a bulky silsesquioxane end group. The azide-functionalized polysiloxane, [–O–SiMe{(CH₂)₃N₃}–]_n[–O–SiMe₂–]_m also undergoes a click reaction with 1 to produce the side chain polyrotaxane. Cyclic voltammograms of these rotaxanes and 1 [(DB24C8)1] show the Fe(II)/Fe(III) redox at the same potential, but with different current depending on their molecular weights. Addition of PdCl₂(MeCN)₂ to a solution of the side-chain polyrotaxane forms gel which regenerates the sol upon addition of PPh₃.