Structural studies on supramolecular adducts of cyclodextrins with the complex [Ru([9]aneS3)(bpy)Cl]Cl

The complex [Ru([9]aneS3)(bpy)Cl]Cl (bpy = 2,2′-bipyridine) was immobilised in plain β-cyclodextrin (β-CD) and permethylated β-CD (TRIMEB) to yield two adducts with a 1:1 host:guest stoichiometry. The adducts were studied by powder X-ray diffraction (XRD), thermogravimetric analysis (TGA), 13C{1H} CP/MAS NMR and vibrational spectroscopy (FT-IR and Raman). Results support the formation of stable supramolecular adducts with a proposed geometry in which the coordinated bypiridine fragment of the guest is partially included in the host cavities, and the bulky [9]aneS3 fragment protrudes out to the interstitial spaces. A packing mode is proposed for [Ru([9]aneS3)(bpy)Cl]Cl · TRIMEB, obtained by Monte Carlo optimisation of the XRD data. TRIMEB molecules are stacked in tilted channels, with the voluminous part of the guest molecules in the inter-channel space. The behaviour of [Ru([9]aneS3])(bpy)Cl]Cl upon CD encapsulation and the chloride ligand hydrolysis process in solution for all compounds were studied in detail by Raman spectroscopy.