A novel probe based on rhodamine 101 spirolactam and 2-(2′-hydroxy-5′-methylphenyl)benzothiazole moieties for three-in-one detection of paramagnetic Cu2+, Co2+ and Ni2+

Abstract 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 Cu2+, Co2+ and Ni2+ through different processes. Ratiometric changes in emission intensities at 565 nm and 460 nm for 1 (λex = 350 nm) were observed in presence of Co2+, Cu2+ and Ni2+ respectively. This probe displayed ratiometric colorimetric responses and ‘turn-on’ fluorescence responses (λex = 540 nm) toward Cu2+ and Co2+. Whereas probe 1 exhibited very weak absorption around 480 nm, no ‘turn-on’ emission (λex = 540 nm) in presence of Ni2+. The detection limits were 0.11 μM and 0.17 μM for Cu2+ and Co2+ ions respectively from ratiometric colorimetric measurements and 26 nM, 54 nM and 101 nM for Cu2+, Co2+ and Ni2+ respectively from ratiometric fluorometric measurements. The excited-state intramolecular proton transfer (ESIPT)-prohibited coupled ring-open process for 1–Cu2+ (1–Co2+) and ESIPT-prohibited irreversible process for 1–Ni2+ were proposed according to the spectral results. Furthermore, probe 1 was utilized to determine Cu2+ and Co2+ in real-life samples with good recoveries.