A rhodamine based fluorescent and colorimetric chemosensor for the detection of Cr ions and its utility in a molecular logic gate.

A new rhodamine based fluorescent and colorimetric chemosensor S1 was synthesized for the selective recognition of Cr, a trivalent metal ion. The interaction of S1 toward different metal ions has been studied fluorescence and UV-visible spectroscopy. The studies revealed that the fluorescence and colorimetric changes of chemosensor S1 are prominent for Cr over other competitive metal ions. Moreover, the chemosensor S1 exhibits 1 : 1 complex formation with Cr as apparent from the Job's plot and the Benesi-Hildebrand (B-H) plot. Density functional theory (DFT) studies also revealed that the Cr ion is coordinated to three atoms of S1, which validates the formation of a complex between S1 and Cr. The limit of detection (LOD) of chemosensor S1 for Cr was 0.21 μM. Furthermore, to explore the recyclability of S1, ethylenediaminetetraacetic acid (EDTA) was added to the S1-Cr3+ solution. On the addition of EDTA to the solution of S1-Cr3+, the reversibility of the complex was observed, and a colorimetric variation was also observed on the addition of Cr and EDTA to S1 which mimics the "INHIBIT "molecular logic gate. Chemosensor S1 also demonstrated practical utility through detection of Cr in the solid state.