The Fluorescence Properties of Free and Cation-complexed Lariat Ethers having Sidearms Terminated by a Benzene Ring

Abstract

Fluorescence and visible spectra of phenyl-sidearmed lariat ethers and of toluene, ethylbenzene, and propylbenzene were obtained in dichloromethane and acetonitrile solutions. Changes in their spectra were observed in the presence of KSCN or CF₃COOH in an effort to obtain solution confirmation of cation–pi interactions. The lariat ether receptor molecules, Ph(CH₂)_1–3 < N18N>(CH₂)_1–3Ph gave quite different results even though they varied only in the sidearm chain length. In previous studies, solid state cation–pi complexes were obtained only with Ph(CH₂)₂ < N18N>(CH₂)₂Ph and not with either PhCH₂ < N18N > CH₂Ph or Ph(CH₂)₃ < N18N>(CH₂)₃Ph. Variations in behavior in solution were noted among the three lariat ethers in the presence of different Lewis acids but definitive evidence for cation–pi interactions proved elusive.

Keywords:

• Fluorescence
• Lariat ether
• Receptor
• Crown ether
• Cation–pi
• Cation–complexation

Acknowledgements

We thank the National Science Foundation for grant CHE-0415586, that supported this work.