Ethynylpyrene Linked Benzocrown Ethers as Fluorescent Sensors for Metal Ions

Abstract

Substances containing ethynylpyrenes linked to either one or four benzocrown ethers were synthesized, and their absorption and fluorescence spectroscopic responses to metal ions were assessed. Addition of metal perchlorates to solutions of these substances promotes short wavelength shifts in their absorption and fluorescence maxima and increases in their fluorescence intensities. The magnitudes of the fluorescence intensity increases are dependent on the ring size and number of the crown ether and the nature of the metal cation. Association constants for complex formation were calculated using fluorescence intensity versus concentration data. Analysis using Job's plots showed that the substances containing one benzocrown ether moiety form 1:1 complexes with metal ions. Results of experiments employing repeated addition and removal of Mg(ClO4)2 demonstrate that the ON‐OFF fluorescence response can be repeated at least three times. Results of molecular orbital calculations show that complexation with metal ions lowers the energies of both the π and π* levels of the ethynylpyrene moiety and that in some cases the vacant orbital on the metal becomes the LUMO of the complex. An explanation of the spectroscopic changes promoted by metal ions is proposed in terms of electrostatic repulsion and structural regulation.

Multiple Stimuli-Responsiveness Fluorescent Probe Derived from Cyclopolymers and Pyrene-Ended Ammonium Salts

“…Pyrene and its derivatives are often used as fluorescent materials because of their photochemical inertness, dual luminescence, and high emission quantum yields. − Especially in recent years, supramolecular chemical sensors based on pyrene monomer-excimer dual luminescence have attracted increasing attention. , Moreover, these sensors have been well applied for the detection of metal ions, − explosives, and biological particles. , However, to our knowledge, there are few reports , about the multiple stimuli -responsive ratiometric sensors based on pyrene.…”