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