MLCT based colorimetric probe for iron having D–A–D type architecture of benzo[2,1,3]thiadiazole acceptor and thiophene donor with azomethine pendant arm

A new chemosensor 3 having D–A–D type architecture of benzo[2,1,3]thiadiazole acceptor and thiophene donor with azomethine pendant arm was synthesized and its metal recognition capability was studied over the first row transition metal series. Compound 3 showed colorimetric sensitivity and selectivity towards for Fe(II) and Fe(III). Change in the strength of intramolecular charge transfer (ICT) due to metal to ligand charge transfer (MLCT) is responsible for color change. It has been established using CV and NMR titration. The sensitivity of 3 is in the range of μM concentration that leads to the visual detection by changing color from yellow to orange.