(Oligo)thienyl-imidazo-benzocrown ether derivatives: synthesis, photophysical studies and evaluation of their chemosensory properties.

A series of novel (oligo)thienyl-imidazo-benzocrown ethers were synthesised through a simple method and evaluated as fluorimetric chemosensors for transition metal cations. Interaction with Ni(2+), Pd(2+), and Hg(2+) in ACN/DMSO solution (99:1) was studied by absorption and emission spectroscopy. Chemoselectivity studies in the presence of Na(+) were also carried out and a fluorescence enhancement upon chelation (CHEF) effect was observed following Hg(2+) complexation. Considering that most systems using fluorescence spectroscopy for detecting Hg(2+) are based on the complexation enhancement of the fluorescence quenching (CHEQ) effect, the present work represents one of the few examples for sensing of Hg(2+) based on a CHEF effect.