ANION RECOGNITION BY UREA AND THIOUREA GROUPS - REMARKABLY SIMPLE NEUTRAL RECEPTORS FOR DIHYDROGENPHOSPHATE

A bis-urea and a bis-thiourea host, both derived in only one step from 1,3-bis(aminomethyl)benzene, are shown to bind dihydrogenphosphate se lectively over various other anions (H2PO4- > CH3COO- > Cl- > HSO4- > NO3- > ClO4-). The much stronger binding of H2PO4- by the bis-thiourca is rationalized by the stronger H-bond donor strength of the thiourea groups and the binding selectivity is explained in terms of the compl ex geometry and the basicity of the guest anions. The lack of self-ass ociation and the changes in the UV spectrum upon complexation make bis -thiourea hosts a promising new class of neutral receptors for dihydro genphosphate.