312 ’ ACCOUNTS OF CHEMICAL RESEARCH ’ 312–326 ’ 2013 ’ Vol. 46, No. 2 Published on the Web 11/14/2012 www.pubs.acs.org/accounts 10.1021/ar300130w & 2012 American Chemical Society Exploiting the Reversible Covalent Bonding of Boronic Acids: Recognition, Sensing, and Assembly STEVEN D BULL, † MATTHEW G. DAVIDSON, † JEAN M. H. VAN DEN ELSEN, ‡ JOHN S. FOSSEY, § A. TOBY A. JENKINS, † YUN-BAO JIANG, ^ YUJI KUBO, ) FRANK MARKEN, † KAZUO SAKURAI, # JIANZHANG ZHAO, 3 AND TONY D. JAMES* , † † Department of Chemistry, University of Bath, Bath BA2 7AY UK, ‡ Department of Biology and Biochemistry, University of Bath, Bath BA2 7AY UK, § School of Chemistry, University of Birmingham, Edgbaston, Birmingham, West Midlands, B15 2TT, UK, ) Department of Applied Chemistry, Graduate School of Urban Environmental Sciences, Tokyo Metropolitan University, 1-1 Minami-ohsawa, Hachioji, Tokyo 192-0397, Japan, ^ Department of Chemistry, College of Chemistry and Chemical Engineering and the MOE Key Laboratory of Analytical Sciences, Xiamen University, Xiamen 361005, China, # Faculty of Environmental Engineering, The University of Kitakyushu, 1-1 Hibikino, Wakamatsu, Kitakyushu City, Fukuoka, 808-0135 Japan, and 3 State Key Laboratory of Fine Chemicals, School of Chemical Engineering, 2 Ling-Gong Road, Dalian University of Technology, Dalian 116024, China RECEIVED ON MAY 15, 2012 CONSPECTUS B oronic acids can interact with Lewis bases to generate boronate anions, and they can also bind with diol units to form cyclic boronate esters. Boronic acid based receptor designs originated when Lorand and Edwards used the pH drop observed upon the addition of saccharides to boronic acids to determine their association constants. The inherent acidity of the boronic acid is enhanced when 1,2-, 1,3-, or 1,4-diols react with boronic acids to form cyclic boronic esters (5, 6, or 7 membered rings) in aqueous media, and these interactions form the cornerstone of diol-based receptors used in the construc- tion of sensors and separation systems. In addition, the recognition of saccharides through boronic acid complex (or boronic ester) formation often relies on an interaction between a Lewis acidic boronic acid and a Lewis base (proximal tertiary amine or anion). These properties of boronic acids have led to them being exploited in sensing and separation systems for anions (Lewis bases) and saccharides (diols). The fast and stable bond formation between boronic acids and diols to form boronate esters can serve as the basis for forming reversible molecular assemblies. In spite of the stability of the boronate esters' covalent BO bonds, their formation is reversible under certain conditions or under the action of certain external stimuli. The reversibility of boronate ester formation and Lewis acidbase interactions has also resulted in the development and use of boronic acids within multicomponent systems. The dynamic covalent functionality of boronic acids with structure- directing potential has led researchers to develop a variety of self-organizing systems including macrocycles, cages, capsules, and polymers. This Account gives an overview of research published about boronic acids over the last 5 years. We hope that this Account will inspire others to continue the work on boronic acids and reversible covalent chemistry.