Development of phenanthridine-based highly selective "Turn-ON" fluorescence chemosensor for the detection of Ru³⁺ in...

A phenanthridine-based fluorogenic probe 5-(2-(prop-2-yn-1-yloxy)phenyl)-7,8,13,14-tetrahydrodibenzo[a,i]phenanthridine (SAAPH) has been successfully synthesized and characterized through nuclear magnetic resonance (NMR) and high resolution mass spectrometry (HRMS) spectral analyses. A low detection limit was attained for identifying Ru³⁺ at a concentration of 151pM with a minimal reaction time of 10 s. Furthermore, incorporating ethylenediaminetetraacetic acid (EDTA) into SAAPH + Ru³⁺ rendered SAAPH a reversible sensor. Fascinatingly, the fluorescence signal of SAAPH was Turn-ON by the interaction with Ru³⁺ resulting in the noticeable emission change from colorless to blue with an emission enhancement fold of 12. The detection mechanism of SAAPH was initiated by an Intramolecular Charge Transfer (ICT), wherein electrons were transferred from the electron-rich phenanthridine moiety containing the propargylic group to the electron-deficient Ru³⁺. Additionally, paper strips were used for fluorescence detection of Ru³⁺. Further, Ru³⁺ was detected in environmental water samples and HeLa cells. Consequently, SAAPH demonstrates a lower detection limit than other fluorescent probes and exhibits strong selectivity and sensitivity toward Ru³⁺.