Self-assembling of highly substituted 2-hydroxypropyl-β-cyclodextrin in the presence of in situ-formed iron oxide nanoparticles to produce magnetically ordered water-soluble supramolecular adducts

High-substituted 2-hydroxypropyl-β-cyclodextrin (HP-β-CD) was shown to self-assemble in aqueous solutions in the presence of in situ-formed insoluble species of iron. Two different types of water-soluble high-molecular compounds were synthesized at room temperature in aqueous aerated alkaline solutions of (NH 4 ) 2 Fe(SO 4 ) 2 •6H 2 O and high-substituted 2-hydroxypropyl-β-cyclodextrin (HP-β-CD) in the presence of NaH 2 PO 2 . These substances called adducts proved to be inorganic-organic hybrid nanospecies of iron species, HP-β-CD and encapsulated inorganic salts (sulfates and phosphates of sodium and ammonium). The adducts were established to show different properties and to have diverse compositions depending on the HP-β-CD: Fe molar ratio in starting solution. The first synthesized adduct (I) is characterized by an unambiguous magnetism with lower solubility in water. It gives a homogeneous solution with particles 400 nm in diameter. The second adduct (II) is not magnetic, more soluble in water, and forms nanoparticles of ∼760 nm in diameter. Both adducts are stable in aqueous solutions but totally destroyed in the presence of H 2 O 2 , K 2 S 2 O 8 , and AgNO 3 . By addition of BaCl 2 excess to the aqueous solutions of I and II, the residue of BaSO 4 is precipitated and dimensions of the particles of both types decrease up to ∼230 and ∼570 nm in diameter, respectively. Solids I and II were characterized by the data of X-ray diffraction (XRD), Mössbauer spectroscopy, SEM, IR-spectra, and magnetic measurements. Aqueous solutions of I and II were studied by means of mass-spectrometry (MALDI-TOF), dynamic light scattering (DLS) measurements, and analyzed by spectrophotometric titration with phenolphthalein.