Synthesis, structural characterization, solvatochromism, and ion-binding studies of a ditopic receptor based on 2-(4-[2,2′: 6′,2′′]terpyridin-4′-yl-phenyl)-1H-phenanthro[9,10-d] imidazole (tpy-HImzphen) unit

Abstract

A terpyridyl-imidazole based ditopic receptor 2-(4-[2,2′:6′,2′′]terpyridin-4′-yl-phenyl)-1H-phenanthro[9,10-d]imidazole (tpy-HImzphen) has been synthesized and characterized using standard analytical and spectroscopic techniques and also by single crystal X-ray crystallography. The receptor shows multi-channel sensing ability towards F⁻ and Fe²⁺ ions. Both the anion and cation binding properties of the receptor were thoroughly investigated in dimethylformamide–acetonitrile (1 : 9) solution using absorption, emission, and ¹H NMR spectral studies. In the presence of excess of F⁻ ions, deprotonation of the imidazole N–H fragment occurs, an event which is signalled by the development of bright yellow color visible with the naked eye. Anion-induced lifetime enhancing makes the receptor a suitable lifetime-based sensor for F⁻ ions. The absorption and emission titration of the receptor with Fe²⁺ ion indicates that single conversion of free tpy-HImzphen (colorless) to Fe²⁺ complex (deep violet color) of 2 tpy-HImzphen : 1 Fe²⁺ stoichiometry. The influence of different solvents on the absorption and emission spectral behavior and on the lifetime of the receptor and its Zn(II) complex have also been investigated in detail.