A new multifunctional phenanthroline-derived probe for colorimetric sensing of Fe2+ and fluorometric sensing of Zn2+

Abstract

A new phenanthroline derivative bearing imidazole group, (2-(3,5-di(pyridin-4-yl)phenyl)-1-p-tolyl-1H-imidazo[4,5-f][1,10]phenanthroline) (1), has been devised. 1 can be used as a multifunctional probe exhibiting a highly sensitive colorimetric response to Fe²⁺ and a selectively ratiometric fluorescent response to Zn²⁺ in a buffer-ethanol solution. The absorption enhancement accompanied by a visual color change from colorless to red upon addition of Fe²⁺, makes 1 a suitable naked-eye sensor for Fe²⁺. Moreover, 1 displayed a Zn²⁺-induced red-shift of emission (44 nm) showing a color change from blue to light cyan under a 365-nm UV lamp. Its practical imaging applicability for intracellular Zn²⁺ was confirmed in HeLa cells using a confocal microscope. The improved emission properties and cell imaging capability would provide a new approach for fluorescence sensation for Zn²⁺.