C3-symmetric triaminoguanidine based colorimetric and fluorometric chemosensor: Sequential detection of Zn2+/PPi, its RGB performance for detection of Zn2+ ion and construction of IMPLICATION logic gate

Abstract In this work, new ethyl(E)-2-cyano-3-(1H-pyrrol-2-yl)acrylate appended C3-symmetric star-shape triaminoguanidine based Schiff base (LH3) was designed and synthesized from simple synthons. New probe, LH3 was completely analyzed by 1H NMR, 13C NMR and mass spectrum. In the present probe LH3, effective π-conjugated ethyl(E)-2-cyano-acrylate unit was introduced on the periphery of the pyrrole-triaminoquanidine conjugates by using carefully chosen building units. The probe LH3 shows high selectivity and sensitivity towards Zn2+ ion via colorimetric and fluorometric changes. The yellowish orange color of LH3 solution turned to wine red color upon addition of Zn2+ solution, along with red shifted absorption maxima from 450 nm to 550 nm, this indicates the formation of LH3-Zn2+ species. Job's plot and mass spectrum analysis confirms the formation of 1:3 stoichiometric complex between the LH3 and Zn2+ ions. Further this ensemble shows selective detection towards PPi anion over the other anions based on displacement metal ion approach. Hence, reversible colorimetric/emission response of LH3 towards Zn2+ and PPi ions via “on-off-on” manner could allow the construction of IMPLICATION logic gate functions. The practical efficacy of the probe LH3 was established by utilization of the probe for the detection of Zn2+ ions in real water sample analysis. Further, the significant noticeable colorimetric changes of the probe LH3 upon addition of Zn2+ ion have been successfully integrated with a smartphone app RGB color value to construct a real-time analysis of Zn2+ ions.