A multifunctional colorimetric receptor 1 (2-(3-nitro-2-oxo-2H-chromen-4-ylamino)-3-aminomaleonitrile) for the detection of both Al3+ and F− has been developed. The receptor 1 showed a significant color change in the presence of Al3+ over most other competitive metal ions including Ga3+ and In3+ in aqueous solution. The selectivity mechanism of 1 for Al3+ might be attributed to the enhancement of the intramolecular charge transfer band. Interestingly, it could be recycled simply through treatment with an appropriate reagent such as ethylenediaminetetraacedtic acid. Moreover, 1 showed a highly selective colorimetric response to F− due to the decrease in the intramolecular charge transfer band by a deprotonation process without any interference from other anions. Therefore, 1 can serve as a ‘single sensor for dual targets’.
