A new tripodal 8-hydroxyquinoline as a high sensitivity fluorescence sensor for Zn(II) in ethanol and its two morphology in solid

Abstract

New tripodal ligand form two different dinuclear Zn 2+ complex in solid, but identical in solution. The strong chelate significantly increased fluorescence sensitivity toward Zn 2+ in ethanol solution. • New tripodal ligands (HL) were synthesized from 8-hydroxyquinoline and bis(pyridin-2-ylmethyl)amine. • HL forms stable Zn(II) complexes which has very strong fluorescence in ethanol. The LOD for Zn(II) fluorescence is 2.3 nM. • Symmetric/asymmetric dinuclear Zn(II) complexes with identical formulae can be isolated from CH 3 CN solution, but they are identical in solution. A new tripodal chelate HL was synthesized from tridentate chelate bis(pyridin-2-ylmethyl)amine (BPA) and 8-hydroxyquinoline (8-HQ) to increase interaction between HL and Zn 2+ and improve fluorescence sensitivity. Asymmetric and symmetric dinuclear Zn(II) complex in rod and block shape were formed in CH 3 CN with identical formula, 1 H NMR and fluorescence spectra in solution, but different IR, TG, and PXRD in solid. The fluorescence quantum yields are 0.0145 and 0.602 for HL and [ZnL] 2 2+ in ethanol respectively. LOD reached 2.3 nM Zn 2+ , which is the highest sensitivity. The 7-position functionalization of 8-HQ is critical to the strong coordination and high fluorescence sensitivity.