A new type of thiacalixarene-based chemosensor 2a and 2b containing amino groups as a binding site and 7-nitrobenzo-2-oxa-1,3-diazole (NBD) as a chromophore have been synthesized and characterized by single crystal X-ray diffraction and by NMR spectroscopic methods. Each receptor acted as a strong colorimetric and fluorometric sensor for silver ions and exhibited significant stepwise deprotonation of NH as evidenced by a bathochromic shift in both the UV-vis absorption and fluorescence emission spectra after addition of an Ag+ cation. Furthermore, the metal–ligand complex 2a·Ag+ can be exploited as an ion-pair receptor for the recognition of F−, AcO− or I− anions through switching the detection signal output (can been distinguished by ‘naked eye’). However, receptor 2b·Ag+ displays a selective response only to iodide ion. These results could be attributed to the slightly different structural conformation between receptors 2a and 2b, which are derived from a 1,3-alternate-thiacalixarene scaffold, suggesting they play a key role in the selective and binding ability of the host chemosensors.
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