Thiazolothiazole-Based Fluorescence Probe towards Detection of Copper and Iron Ions through Formation of Radical Cations

This work describes the design and synthesis of fluorescent triphenylamine-thiazolothiazole based donor-acceptor-donor chemosensor 4,4 '-(thiazolo[5,4-d]thiazole-2,5-diyl)bis(N,N-bis(4-methoxyphenyl)aniline) (TTz-1). TTz-1 exhibited positive solvatochromism effect in the excited state due to its strong intramolecular charge transfer (ICT) properties. Potential application of TTz-1 toward metal ion detection were explored systematically. It was established that the addition of Cu(ClO4)(2) (.) 6H(2)O into TTz-1 resulted in near-infrared (NIR) colorimetric and fluorescent quenching allowing for Cu2+ detection. EPR studies indicate that formation of radical cation occurs when Cu2+ and TTz-1 interact. TTz-1 was also able to detect Fe3+ employing a color change from orange to colourless (fluorescent). It was observed that the TTz-1 emission peak at 567 nm was quenched after addition of Cu2+ and Fe3+ metal ions. Electrochemical analysis showed that LUMO values of the TTz-1 decreased after addition of Fe3+ and Cu2+. The limits of detection (LOD) for Cu2+ and Fe3+ detection by TTz-1 were found to be 0.30 mu M and 0.29 mu M, respectively. These results suggest that the TTz-1 is a highly selective and sensitive sensor for the detection of Cu2+ or Fe3+ ions.