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

•Donor–acceptor–donor (D–A–D) system with azomethine pendant arm was synthesized.•Donor and acceptor are thiophene and benzo[1–3]thiadiazole, respectively.•D–A–D molecule acts selective colorimetric probe for Fe(II) and Fe(III).•ICT followed by MLCT is responsible for color change.•CV experiments and NMR titration established the ICT and MLCT.

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.

Graphical abstractBenzo[1–3]thiadiazole containing D–A–D type compound 3 was synthesized by simple and straightforward synthetic strategy. It acts as selective colorimetric probe for iron. Change in the strength of intramolecular charge transfer (ICT) due to metal to ligand charge transfer (MLCT) is responsible for color change.Figure optionsDownload full-size imageDownload as PowerPoint slide