Two novel colorimetric receptors, S1 and S2, linked to one or two nitrophenylurea groups were synthesized in good yields, characterized and their chromogenic properties investigated towards various anions (F-, Cl-, Br-, I-, NO3-, AcO-, ClO4-, HSO4-, and H2PO4-) by UV-vis and 1H NMR techniques. The receptors, effectively and selectively, recognized and distinguished the biologically important F- from other anions such as Cl-, Br-, I- etc. in CH3CN. This selectivity could be easily observed by the naked eye, indicating that receptors S1 and S2 are potential colorimetric sensors for fluoride ion. © 2012 Elsevier Ltd. All rights reserved.