Influence of Chiral Ionic Liquids on the Excited-State Properties of Naproxen Analogs

Abstract

<p>The synthesis and decolorization of chiral room-temperature ionic liquids based upon 1-methyl imidazole and chloromethyl menthyl ether is reported. The excellent optical quality of these solvents permits the investigation of the effects of the two enantiomers on the excited-state photophysics of (<em>S</em>)-<em>N</em>-methyl-2-pyrrolidinemethyl 2(<em>S</em>)-(6-methoxy-2-naphthyl)propionate [(<em>S</em>,<em>S</em>)-NPX-PYR]. Whereas in conventional bulk polar solvents such as acetonitrile, (<em>S</em>,<em>S</em>)-NPX-PYR is known to execute excited-state intramolecular electron transfer and to form exciplexes, in these chiral solvents these nonradiative processes are absent. The chiral solvents do, however, induce a small but reproducible (∼10%) stereodifferentiation in the fluorescence lifetime of (<em>S</em>,<em>S</em>)-NPX-PYR as well as in the parent compound, (<em>S</em>)-naproxen. To our knowledge, this is the first example of chiral ionic liquids inducing such an effect on photophysical properties.</p>