Solvent-dependent selective “naked eye” chromofluorogenic multifunctional rhodamine-based probe for Al3+, Cu2+, Hg2+, S2− and CN− ions

Abstract

The solvent-dependent selective “naked eye” chromofluorogenic multifunctional rhodamine-based probe 3 for Al3+, Cu2+, Hg2+, S2− and CN− ions was synthesized and its spectral, luminescent and ionochromic properties were studied. The compound obtained exists in the spirolactam form, confirmed by data of 1H, COSY, HSQC, HMBC and 13C NMR spectroscopy. In ethanol, Al3+ ions selectively, even in the presence of other metal cations (Na+, Ba2+, Zn2+, Cd2+, Ni2+, Co2+, Cu2+, Hg2+ and Fe3+) initiate the opening of the spirolactam ring, accompanied by the appearance of a new absorption band at 556 nm and the “naked eye” effect with a change in the yellow-green color of the solution to orange-pink. At the same time, the initial fluorescence 3 at 539 nm shifts to the longer 579 nm spectral region. The use of acetone as a solvent allows the selective detection of copper(II) cations that turn the yellow color of a solution of 3 to pink-purple (λabs 563 nm) due to the formation of the ring-open complex 3.Cu2+ that exhibits emission at 580 nm. Selective detection of Hg2+ in acetonitrile results in the “naked eye” effect characterized by a change in the color of the solution from bright yellow to pink-cherry (λabs 564 nm). The fluorescence of the mercury(II) complex is observed at 587 nm. Complexes 3.Cu2+ and 3.Hg2+ were used for the sequential selective recognition of S2− and CN− anions, respectively. A combinatorial molecular logic gate was designed based on the cation/anion sensing ability of probe 3.