A novel probe based on rhodamine 101 spirolactam and 2-(2'-hydroxy-5'-methylphenyl)benzothiazole moieties for three-in-one detection of paramagnetic Cu, Co and Ni.

A novel probe based on rhodamine 101 spirolactam and 2-(2'-hydroxy-5'-methylphenyl)benzothiazole moieties (probe 1) was developed as a three-in-one platform for detection of paramagnetic Cu, Co and Ni through different processes. Ratiometric changes in emission intensities at 565 nm and 460 nm for 1 (λ = 350 nm) were observed in presence of Co, Cu and Ni respectively. This probe displayed ratiometric colorimetric responses and 'turn-on' fluorescence responses (λ = 540 nm) toward Cu and Co. Whereas probe 1 exhibited very weak absorption around 480 nm, no 'turn-on' emission (λ = 540 nm) in presence of Ni. The detection limits were 0.11 μM and 0.17 μM for Cu and Co ions respectively from ratiometric colorimetric measurements and 26 nM, 54 nM and 101 nM for Cu, Co and Ni respectively from ratiometric fluorometric measurements. The excited-state intramolecular proton transfer (ESIPT)-prohibited coupled ring-open process for 1-Cu (1-Co) and ESIPT-prohibited irreversible process for 1-Ni were proposed according to the spectral results. Furthermore, probe 1 was utilized to determine Cu and Co in real-life samples with good recoveries.