Fluorescence spectroscopic properties of the complex formation between six new C-pivot16-crown-5 ethers bearing fluorescence side arms and metal ions are studied. Six new C-pivot 16-crown-5 ethers that carry fluorescence side arms were synthesized. The research also included the examination of different fluorescent behavior of the new lariat ethers in the presence of silver and sodium ions (Ag+ and Na+) in methanol. Because of the good fit of the cavity size of these 16-crown-5 ethers with the Ag+ and Na+ ions, remarkable change in fluorescent spectra were observed. The results showed that the new lariat crown ethers exhibited enhanced selectivity towards sodium ion, but silver ion show quenching abilities towards the ligands. Cooperative participations of the C-pivot side arm oxygen with the ring oxygen molecules in complexation was also confirmed by the single crystal X-ray crystallography of the complex, (C27H30O7)·NaClO4. The freezing of crown ring conformation and the diminishment of the chance of sidearm oscillation that occurred upon complexation with sodium ion are the main causes of fluorescent enhancement. The quenching caused by the addition of silver ion was found to explainable by the photo-induced electron transfer that results in the reduction of silver ions.
Journal of Luminescence, Volume 121, Issue 1, Pages 159-172