Synthesis of a Phenylhydrazone‐based Colorimetric Anion Sensor with Complementary IMP/INH Logic Functions

A dinitrophenyl hydrazone colorimetric anion sensor (receptor 1 ) was synthesized and its recognition properties towards various anions were investigated by naked eye observation and spectroscopic methods, namely UV‐vis and ¹H NMR titrations in DMSO. The addition of AcO^?, F^? and H₂PO₄^? to receptor 1 resulted in marked red shift of the charge‐transfer absorbance band (Δλ=91 nm, 407 nm to 498 nm) concomitant with a 'naked‐eye' detectable colour change from yellow to pink. However, both the colour and spectral changes were reversible by the addition of cations (M^II) of 3d^5‐10 as well as Cd^II, Hg^II, Mg^II and Ca^II. Subsequently, complementary IMP/INH logic functions based on colour and spectral switching (ON/OFF) were affirmed. The sensor can, thus be utilized as a colorimetric molecular switch modulated by F^?/M^II.