Fluorescent chemosensors 1 and 2, with 1,2,4-oxadiazoles as the binding ligands and anthracene as the fluorophore, were synthesized through sequential 1,3-dipolar cycloaddition reactions of 25,27-dioxyacetonitrilecalixarenes 8 and 11. The fluorescence of 1 was severely quenched by both Fe 3+ and Cu 2+ , whereas that of 2 was selectively quenched only by Fe 3+ . Control compound 4 was also selectively quenched by Fe 3+ , which implied the importance of anthryl-1,2,4-oxadiazole core; furthermore, it was shown to give various oxidation products such as oxanthrone 13, anthraquinone 14, and imidazolyl oxanthrone 15. In addition to product separation and identification, the fluorescent quenching mechanism of these 9-anthryl-1,2,4-oxadiazolyl derivatives by Fe 3+ is also discussed. Furthermore, it should be noted that the oxadiazole-substituted anthracene 4 and calixarene 2 are Fe 3+ -selective fluorescent chemodosimeters without the interference by Cu 2+ .