title: Synthesis and supramolecular studies of chiral boronated platinum(II) complexes: insights into the molecular recognition of carboranes by β-cyclodextrin.
abstract: The synthesis and characterisation of a novel isomeric family of closo-carborane-containing Pt(II) complexes ((R/S)-(1-4)⋅2 NO(3)) are reported. Related complexes (5⋅NO(3) and 6⋅NO(3)) that contain the 7,8-nido-carborane cluster were obtained from the selective deboronation of the 1,2-closo-carborane analogues. The corresponding water-soluble supramolecular 1:1 host-guest β-cyclodextrin (β-CD) adducts ((R/S)-(1-4)⋅β-CD⋅2 NO(3)) were also prepared and fully characterised. HR-ESI-MS experiments confirmed the presence of the host-guest adducts, and 2D-(1) H{(11)B} ROESY NMR studies showed that the boron clusters enter the β-CD from the side of the wider annulus. Isothermal titration calorimetry (ITC) experiments revealed enthalpically driven 1:1 and higher-order supramolecular interactions between β-CD and (R/S)-(1-4)⋅2 NO(3) in aqueous solution. A comparison of the predominate 1:1 binding mode established that the affinity of β-CD for the guest molecule is mainly influenced by the pyridyl ring substitution pattern and chirality of the host, whilst the nature of the closo-carborane isomer also plays some role, with the most favourable structural features for β-CD binding being the presence of the 4-pyridyl ring, 1,12-closo-carborane, and an S configuration. The results reported here represent the first comprehensive calorimetric study of the supramolecular interactions between closo-carborane compounds and β-CD, and it provides fascinating insights into the structural features influencing the thermodynamics of this phenomenon.
authors.affiliation: School of Chemistry, The University of Sydney, Sydney, NSW 2006, Australia.
authors.forename: H Y Vincent
authors.initials: HY
authors.lastname: Ching
authors.forename: Sarah
authors.initials: S
authors.lastname: Clifford
authors.forename: Mohan
authors.initials: M
authors.lastname: Bhadbhade
authors.forename: Ronald J
authors.initials: RJ
authors.lastname: Clarke
authors.forename: Louis M
authors.initials: LM
authors.lastname: Rendina
mesh_terms: D001880:Boranes / Q000737:chemistry*; D002151:Calorimetry; D056831:Coordination Complexes / Q000138:chemical synthesis* / Q000737:chemistry; D018360:Crystallography, X-Ray; D008968:Molecular Conformation; D010984:Platinum / Q000737:chemistry*; D013237:Stereoisomerism; D013816:Thermodynamics; D014867:Water / Q000737:chemistry; D047392:beta-Cyclodextrins / Q000737:chemistry*
chemical_list: D001880:Boranes; D056831:Coordination Complexes; D047392:beta-Cyclodextrins; D014867:Water; D010984:Platinum; C031215:betadex