A Chirality/Light Dual-Responsive Calixarene-Functionalized Gold Surface for the Separation of Naproxen Enantiomers

Chiral and photo-responsive calix[4]arene (trans CAC4) host system that can be adsorbed onto gold surfaces was rationally designed and produced in quantitative yields. Chiral recognition through strong host-guest interaction between trans CAC4 and (R)-naproxen was confirmed by fluorescence titration and ¹ H NMR analysis. Functionalization of the gold surface with trans CAC4 was demonstrated by increased contact angle and XPS measurement. Photoswitching by trans-cis isomerization of CAC4 and CAC4-modified gold surfaces was confirmed by UV-vis spectroscopy and contact angle experiments. Trans CAC4-modified gold surfaces showed selective adsorption towards (R)-naproxen, while cis CAC4-modified gold surfaces did not show any distinctive interaction with (R)/(S)-naproxen. Langmuir isothermal plots and LSCM studies proved quantitative adsorption of (R)-naproxen by the trans CAC4-modified surface. This study demonstrated chiral recognition of a drug system by visual macroscopic changes, which may be used as a convenient methodology to separate bioactive enantiomers.