Neutral cryptand-like cyclic peptide–thiourea receptors for selective recognition of sulphate anions in aqueous solvents

Abstract

The synthesis and anion complexation properties of two hybrid cyclic peptide–thiourea cryptands have been studied. Receptors encapsulate sulphate via nine hydrogen bonds and show selectivity for this anion in solvent mixtures containing up to 20% H₂O/deuterodimethyl sulphoxide. In this solvent mixture, chloride, bromide and acetate are encapsulated via six hydrogen bonds and with lower affinity than sulphate.

Keywords:

• anion recognition
• thiourea
• cyclic peptide
• sulphate

Acknowledgements

We thank Dr Ian Luck (USyd) for technical assistance with NMR and the Australian Research Council for financial support.

Notes

1. Crystallographic information files reported in the present manuscript have been deposited with the Cambridge Crystallographic Data Centre as supplementary publication number CCDC 831167. Copies of the data are available free of charge from the CCDC, 12 Union Road, Cambridge, CB2 1EZ, UK (Fax: [phone]; email: [email protected]).