N-(4-amino-7-nitrobenzaoxa-1,3-diazole)-substituted aza crown ethers: complexation with alkali, alkaline earth metal ions and ammonium
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Three novel aza-crown ether derivatives incorporating 4-amino-7-nitrobenzaoxa-1,3-diazole (NBD) chromophore were synthesized and their structure confirmed by 1H-NMR, IR and elemental analysis. The influence of the solvent polarity and protonation on the photophysical properties of NBD-15-crown-5 was studied by UV/Vis and fluorescence methods. The influence of the investigated cations on the absorption spectra of the ligands was negligible, however emission was strongly affected. Complexation and binding stability of NBD-aza-15-crown-5 and NBD-aza-18-crown-6 were studied using fluorescence spectroscopy. NBD-aza-18-crown-6 exhibits strong selectivity toward Ca2+ and Sr2+ ions with formation constants about 103 times higher than the formation constants with the other ions included in the study.
KeywordsAza-crown ethers Complexation Metal ions Fluorescence Absorption
This research was supported by Title III program at Florida A&M University. The authors also would like to thank Dr. Maurice Edington for his constant support and encouragement as well as Dr. Wang Zang from the College of Pharmacy and Pharmaceutical Sciences for recording the NMR spectra.
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