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 1 H NMR titrations in DMSO. The addition of AcO − , F − and H 2 PO 4 − to receptor 1 resulted in marked red shift of the charge‐transfer absorbance band (Δ λ= 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 .