Recognition and sensing of fluoride anion Massimo Cametti* ab and Kari Rissanen* b Received (in Cambridge, UK) 30th January 2009, Accepted 10th March 2009 First published as an Advance Article on the web 9th April 2009 DOI: 10.1039/b902069a Fluoride anion recognition is attracting a mounting interest in the scientific community due to its duplicitous nature. It is a useful chemical for many industrial applications, and it has been used in human diet, but, recently it has been accused for several human pathologies. Here we describe the ample panorama of different approaches the chemists world-wide have employed to face the challenge of fluoride binding, and we outline some of the research which in our view can contribute to the development of this field, especially when fluoride binding has to be achieved in highly competitive protic solvents and water. Introduction Anion binding has finally become a mature field of research, matching, at least for efforts and variety of receptor species, the earlier developed field of cation recognition. A coordina- tion chemistry of anions, in full analogy to metal coordination chemistry, has been also proposed. 1 However, despite the large number of different receptor/sensor molecules studied and described so far in the literature, there are few systems which display those characteristics and possess those requirements, in terms of selectivity and affinity, easily adaptable to practical applications. This is especially true when recognition in water is considered. The unique properties of water, 2 in terms of polarity, H-bonding abilities, etc., are responsible for a massive load of complications when the binding in such media has to be achieved. The knowledge acquired in the study of a great number of systems in organic solvents can clearly come in hand when dealing with the more troublesome aqueous media, but, so far judging from the results in the literature, it seems unreasonable to simply transfer the examples of successful design from organic solvents to water without additional thinking. Indeed, very few receptors which can achieve anion binding in water have been developed so far. Even more exceptional are those which are able, in water, to bind fluoride, nowadays a very appealing target for synthetic receptors. In the past several years we have witnessed a controversial process by which the general idea that the scientific community a University of Rome ‘‘La Sapienza’’, P. Aldo Moro, 5, 00185 Rome, Italy. E-mail: massimo.cametti@uniroma1.it b Nanoscience Center, Department of Chemistry, University of Jyva ¨skyla ¨, Jyva ¨skyla ¨, Finland FIN-40351. E-mail: kari.t.rissanen@jyu.fi, massimo.m.cametti@jyu.fi; Fax: +358 14 2602651; Tel: +358 14 2602672 Massimo Cametti Massimo Cametti was born in Rome, Italy in 1977. He obtained his PhD from the University of Rome ‘‘La Sapienza’’ in early 2005, studying cation–p interactions and their employment in supramolecular receptors based on salophen-UO 2 com- plexes. After postdoctoral research work in Croatia (Ru: er Bosˇkovic´ Institute, Zagreb), Belgium (Universite´ Libre de Bruxelles, Brussels) and Italy (CNR-IGAG and University of Rome ‘‘La Sapienza’’, Rome), he joined recently the research group of Academy Professor Kari Rissanen at the University of Jyva ¨skyla ¨, Finland. His research interests cover soft-materials, metal coordination, ion-pair and anion recognition. Kari Rissanen Chemistry studies including a PhD in Chemistry were com- pleted at the University of Jyva ¨skyla ¨. He was also a chemistry assistant and assis- tant professor at the Univer- sity of Jyva ¨skyla ¨ between 1985 and 1993. Between 1988 and 1993 he was first a Research Fellow and then a Senior Research Fellow of The Academy of Finland. In 1993 he became an Associate Professor of Organic Chemistry at the University of Joensuu before returning to the Univer- sity of Jyva ¨skyla ¨ in 1995 as Professor and Head of the Laboratory of Organic Chemistry where he is presently. He is also an Academy Professor of The Academy of Finland form 2008 to 2012. Since 1987 he has published more than 310 publications in scientific journals, 18 patents/patent applications and 4150 posters/lectures in scientific conferences. His research topics include structural and synthetic supramolecular, organic and nanochemistry, X-ray crystallography and crystal engineering. This journal is  c The Royal Society of Chemistry 2009 Chem. Commun., 2009, 2809–2829 | 2809 FEATURE ARTICLE www.rsc.org/chemcomm | ChemComm