Synthesis and supramolecular studies of chiral boronated platinum(II) complexes : insights into the molecular recognition of carboranes by β-cyclodextrin

Ching, H.Y. Vincent; Clifford, Sarah; Bhadbhade, Mohan; Clarke, Ronald J.; Rendina, Louis M.

doi:10.1002/CHEM.201201746

Title

Synthesis and supramolecular studies of chiral boronated platinum(II) complexes : insights into the molecular recognition of carboranes by β-cyclodextrin

Author

Ching, H.Y. Vincent

Clifford, Sarah

Bhadbhade, Mohan

Clarke, Ronald J.

Rendina, Louis M.

Abstract

The synthesis and characterisation of a novel isomeric family of closo-carborane-containing PtII complexes ((R/S)-(14)⋅2 NO3) are reported. Related complexes (5⋅NO3 and 6⋅NO3) 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 hostguest β-cyclodextrin (β-CD) adducts ((R/S)-(14)⋅β-CD⋅2 NO3) were also prepared and fully characterised. HR-ESI-MS experiments confirmed the presence of the hostguest adducts, and 2D-1H{11B} 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)-(14)⋅2 NO3 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.

Language

English

Source (journal)

Chemistry: a European journal. - Weinheim

Publication

Weinheim : 2012

ISSN

0947-6539

DOI

10.1002/CHEM.201201746

Volume/pages

18 :45 (2012) , p. 14413-14425