Abiotic guanidinium receptors for anion molecular recognition and sensing

The guanidinium functionality has been utilized by molecular recognition chemists as a strong and selective binder for anionic guests. Guanidiniums, because of their high pK(a), offer both hydrogen-bonding and charge-pairing interactions over a wide range of pH. Strong binding interactions in competitive media have been reported for receptors containing this functionality. Due to the advantageous properties of the guanidinium. group, it has been used in receptor designs for almost every class of small anionic target molecules. This review article will record the history of this group in supramolecular systems by cataloging the target analyte classes for which synthetic guanidinium-based anion receptors have been developed.