Photoswitchable Rhodamine-Based Multianalyte Sensors for Metal Ion Detection

We have developed three azobenzene-core-based molecular systems decorated with different numbers of rhodamine units as photoswitchable multianalyte sensors. Exploiting the ring-opening of the spirolactam part of the rhodamine unit, the resulting fluorescence response, and modulation of it through the photoswitching of azobenzene by light, we utilized them in the detection of multiple metal ions (Fe3+, Fe2+, Sn2+ and Al3+). The binding sites, stoichiometry, binding constants, fluorescent lifetimes and limit of detection (LOD) for each probe have been deduced using appropriate spectroscopic techniques. The limit of detection (LOD) of 5 a, 5 b and 5 c for Fe3+ are found to be 4.2x10(-7)+/- 7.8x10(-9) M, 2.2x10(-7)+/- 4.6x10(-9) M and 1.2x10(-7)+/- 4.6x10(-9) M, respectively. The fluorescence response of the metal-chelated complex can be manipulated effectively by employing the photoswitching ability of azobenzene that makes them useful as chemosensors for various individual metal ions.