Crystal structure and fluorescence sensing properties of tetramethoxyresorcinarene functionalized Schiff bases

A series of tertamethoxyresorcinarene functionalized Schiff bases were conveniently prepared by the reaction of resorcinarene ester derivatives with excess of ethylenediamine and then condensation with salicylaldehyde. The single crystal analysis of five products shows that tetramethoxyresorcinarenes existed in chair conformation. The complexing properties of these polydentated ligands to transition metal ions were studied by UV–Vis and fluorescence spectroscopy. The results demonstrate that these polydentated ligands are more efficient for recognition of Zn2+ in preference to other metal ions, accompanying a remarkable fluorescence intensity enhancement. Taking 4a as an example, it exhibits a 13-fold fluorescence enhancement upon the addition of 3 equiv. of Zn2+ in CH3OH/CH3CN (1:9 v/v) solution.