Copillararene-rhodamine conjugate as selective sensor for Hg2+ ion
A new copillararene coupled rhodamine probe 1 has been designed and synthesized. The molecular probe shows selective sensing of Hg2+ ions over a series of metal ions in CH3CN by exhibiting a color change of the solution as well as ‘turn-on’ fluorescence. Compound 1 also shows interaction with Cu2+ by exhibiting a different color and spectral changes. In the event, Hg2+ ion has been differentiated from Cu2+ by using tetrabutylammonium iodide (TBAI). While in the presence of TBAI the reddish violet color of 1-Cu2+ complex becomes colorless with the regeneration of original electronic spectrum of 1, under identical conditions the pink color of 1-Hg2+ complex is not discharged in presence of TBAI. Model compound 2 with no pillararene moiety has been synthesized to validate the role of pillararene in the selectivity of metal ion sensing. Importantly, compound 2 does not show any selectivity in the sensing under identical conditions. Complexation studies are performed by using UV-vis, fluorescence, FTIR and NMR spectroscopic methods.