Hg(II) ion specific dual mode signalling in a thiophene derivatized rhodamine based probe and their complexation cooperativity

The rhodamine based chemosensor 1 exhibited highly selective and sensitive detection of Hg(II) ion in MeCN–H2O mixture observable through amplified absorption and emission signals with a colour change from colourless to pink. Its thiophenyl subunit plays a predominant role in observed allosteric cooperativity in binding of both the Hg(II) ions of its 1:2 (L:M) complex stoichiometry. The anion induced ‘turn-off’ signalling responses of the Hg(II)-complex of 1 and subsequent ‘turn-on’ responses with further addition of Hg(II) here demonstrated its repetitive usability as a probe for Hg(II) ion detection.