Immobilization of Cryptophane Derivatives onto γ‑Fe2O3 Core–Shell Magnetic Nanoparticles

Three immobilization strategies of cryptophane derivatives onto core–shell γ-Fe2O3/silica magnetic nanoparticles (MNPs) are reported. Immobilization of a cryptophane bearing five methoxy substituents and an alkanethiol chain, 1, was performed onto MNPs coated with a gold nanoshell. Likewise, immobilization of a cryptophane molecule bearing five methoxy substituents and one acid function, 2, onto MNPs coated with APTES was also performed via amide bonds. Finally, the cysteamine coupling agent was used to modify 2, giving 3, before its immobilization onto MNPs coated with a gold nanoshell. Diffuse reflectance infrared transform Fourier spectroscopy (DRIFTS) and transmission electron microscopy (TEM) were used to characterize the chemical modifications of the MNPs for the three immobilization strategies. A very efficient grafting of 1 onto MNPs coated with gold was found whereas the immobilization of 2 and 3 was unsuccessful.