Colorimetric Sensor and Inverse Fluorescent Behavior of Anions by Calix[4]arene Possessing Imidazo[4,5-<i>f</i>]-1,10-phenanthroline Groups and its Ru(II) Complex

Abstract

A calix[4]arene derivative (1) possessing imidazo[4,5-f]-1,10-phenanthroline groups and its Ru(II) complex (2) have been prepared. The photophysical behavior and the binding ability of 1 and 2 with some anions were investigated by fluorescence spectrometry and 1H NMR experiments. The complex stability constants (K S) for the stoichiometric 1:1 complexation of 1 and 2 with the anions were obtained by the fluorimetric titrations, indicating that the binding abilities of both hosts for F− and AcO− are highest among all anions examined. Interestingly, compound 1 can be used as a colorimetric sensor to F− and AcO− due to anion-induced deprotonation of the NH group of the imidazole ring. In contrast, the addition of Cl− , Br− , I− and to the DMF solution of 2 enhances its relative emission intensity, while the addition of F− and AcO− quenches its fluorescence intensity.