Anion Recognition by Synthetic Receptors

Abstract

The important roles played by anions in environmental and natural processes have triggered the interest in the development of synthetic receptor molecules for their selective recognition and transport. Among anionic substrates, sulfate and phosphate have special interest due to their ubiquitous presence in biological systems and also because their well known deleterious effects on the environment. Naturally occurring anion receptors, sulfate-binding protein (SBP) and phosphate-binding protein (PBP), take advantage of the backbone amide NH groups to tightly bind their respective substrates by several hydrogen bonds in a deep cleft. A hydrogen bond acceptor for the phosphate OH in PBP allows the discrimination of phosphate from other similar tetrahedral oxyanions such as sulfate. Conversely SBP has no hydrogen bond acceptors making it unsuitable for protonated oxyanions.

In this work the synthesis of two polyaza cryptand molecules is described. These compounds possess well defined rigid three-dimensional cavities with ammonium binding sites strategically placed for maximum electrostatic and hydrogen bonding interactions with anions. m-xylyl and pyridyl spacers were chosen in order to compare a cavity having only hydrogen bond donors with other where also hydrogen bond acceptors are present. The affinity and selectivity of both receptors for sulfate and phosphate over a series of other anions of different shape, size and charge will be discussed.

Short CV

July 2004 – Degree in Technological Chemistry by the Faculty of Sciences, University of Lisbon;
January 2005 to June 2006 – Trainee at Laboratório da Unidade Fabril de Alverca, CUF – Adubos de Portugal
August 2006 to September 2007 – Graduate Research Student at ITQB, in the Coordination and Supramolecular Chemistry Laboratory
Since October 2007 – Ph.D. Student at ITQB, in the Coordination and Supramolecular Chemistry Laboratory, under the supervision of Prof. Rita Delgado.