A series of the bis(3-indolyl)methene derivatives were synthesized and their anion binding and sensing properties in CH3CN or mixed CH3CN/H2O solution have been investigated in detail by UV-vis spectroscopic techniques. The deprotonation/protonation of the bis(3-indolyl)methene receptor is responsible for the dramatic color and spectral changes. The introduction of the electron-donating or withdrawing group into different moiety of the bis(3- indolyl)methene skeleton, which tunes the acidity of the H-bond donor moiety or the basicity of the H-bond acceptor moiety, has a positive effect on the selectivity and sensitivity of such “proton-transfer” chemosensors for anions.
Keywords: Anion recognition, bis(3-indolyl)methene, colorimetric chemosensor, hydrogen bond, proton transfer, tunable selectivity and sensitivity
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