4-Amino-1,8-naphthalimide-based anion receptors: employing the naphthalimide N-H moiety in the cooperative binding of dihydrogenphosphate

The 4-amino-1,8-naplitlialimide-based anion receptor 3 binds dihydrogenphosphate with 1:1 stoichiometry through cooperative hydrogen bonding to a naplithalimide N-H and thiourea N-H groups. This was clearly established from H-1 NMR titration experiments in DMSO-d(6) where a Substantial shift in the resonance for the naphthalimide N-H was observed concomitant with the expected thiourea N-H chemical shift migration upon successive additions of H2PO4-. However, whilst H-1 NMR titration experiments indicate that 3 was capable of binding other anions such as acetate, the naphthalimide N-H does not participate and the N-H resonance was essentially invariant during the titration. The lack of cooperative binding in this instance was justifiable on steric grounds. (c) 2005 Elsevier Ltd. All rights reserved.