Redox- and pH-Controlled Mechanized Nanoparticles

A new class of mechanized silica nanoparticles, which exploits the stability of the inclusion complexes formed between ferrocenedicarboxylic acid and both cucurbit[7]uril (CB7) and beta-cyclodextrin (beta-CD), are described. Mesoporous silica nanoparticles, capable of storing a payload of small molecules and releasing it following particular activation processes, have been designed and decorated with ferrocenecarboxylic acid stalks. The storage and release of the payload is controlled by the host-guest interaction between the ferrocene moiety (guest) and the ring moiety (CB7 or beta-CD). Ferrocene-based Mechanized NanoParticles (FMNPs) were efficiently prepared, loaded with Rhodamine dye, and then tested under different activation procedures. The systems operated successfully under redox control (oxidation of ferrocenedicarboxylic acid) in the presence of P-CD and under pH control (deprotonation of ferrocenedicarboxylic acid pH > 4) in the presence of CB7. ((c) Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009)