Synthesis and study of indoloquinoxaline based D-π-A type conjugated molecules as fluorescent probe for hypochlorite detection

Abstract

We have successfully synthesized three new donor-π-acceptor (D-π-A) type indoloquinoxaline-based conjugated molecules in which electron rich indoloquinoxaline unit is coupled with different acceptor units such as barbituric acid, thiobarbituric acid and reduced isatin through thiophene spacer. All three molecules are characterized by IR, NMR and mass analysis. The photophysical, electrochemical, thermogravimetric analysis and DFT calculations studies were carried out for the synthesized molecules. The molecules were explored as a chemosensor for the detection of hypochlorite and the sensing mechanisms of these molecules towards hypochlorite were examined by 1H NMR spectra. These molecules exhibit weak fluorescence emission due to a strong intramolecular charge transfer (ICT) effect between indoloquinoxaline moiety and different acceptors. Interestingly, compounds, M1 and M3 showed enhanced fluorescence recognition performance, whereas compound M2 showed quenching fluorescence recognition performance for hypochlorite ion. Our study suggests that altering the D-π-A structure and employing suitable ICT effect can enhance the detection ability of molecules for the target analyte.