An Efficient Fluorescence “Turn-On” Chemosensor Comprising of Coumarin and Rhodamine Moieties for Al3+ and Hg2+

A potent fluorescence ‘turn-on’ receptor (HL) based on rhodamine and coumarin moieties for the detection of Hg2+ and Al3+ is synthesized by condensation of rhodamine 6G hydrazide and 4-hydroxy-3-acetylcoumarin. In presence of Al3+ and/or Hg2+ the receptor (HL) exhibits deep pink colouration and a sharp band at 528 nm is appeared in UV–vis titration. Upon gradual addition of Al3+ and/or Hg2+ to the solution of HL significant enhancement of fluorescence intensity is observed at 564 nm in MeCN:H2O (1:5, v/v) medium. The receptor is strongly bound to Al3+ and/or Hg2+ and the association constants (Ka) are found to be 1.74 × 104 and 1.04 × 104 M− 1 for Al3+ and Hg2+ respectively.