Solvent effect and fluorescence response of the 7-tert-butylpyrene-dipicolylamine linkage for the selective and sensitive response toward Zn( ii ) and Cd( ii ) ions

The different binding behaviour of 7- tert -butylpyrene based chemosensors bearing dipicolylamine (Dpa) linkages at the 1,3-positions was investigated in various solvents for the sensing of Zn( ii ) and Cd( ii ).The potential mono-chelating ligand L1 follows the same binding pattern in both THF and methanol–water solvent systems, exhibiting higher selectivity and sensitivity for Cd( ii ) over Zn( ii ) mainly in THF solvent system. The potential bis-chelate ligand L2 can selectively bind both Zn( ii ) and Cd( ii ) in a 1 : 1 ratio in THF, whereas in methanol–water (7 : 3) at pH = 7.0; a 1 : 2 binding ratio was observed. In THF, two sites of ligand L2 can only selectively and sensitively bind one Zn( ii ) or Cd( ii ). The different complexation behaviour of L1 and L2 in different solvents were studied by means of fluorescence spectra and 1 H-NMR titration experiments in the presence of Zn( ii ) and Cd( ii ).