title: N-(4-amino-7-nitrobenzaoxa-1,3-diazole)-substituted aza crown ethers: complexation with alkali, alkaline earth metal ions and ammonium.
abstract: Three novel aza-crown ether derivatives incorporating 4-amino-7-nitrobenzaoxa-1,3-diazole (NBD) chromophore were synthesized and their structure confirmed by (1)H-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 Ca(2+) and Sr(2+) ions with formation constants about 10(3) times higher than the formation constants with the other ions included in the study.
authors: Department of Chemistry, Florida A&M University, 1530 M.L.King, Jr. Blvd, 219 Jones Hall, Tallahassee, FL 32307, USA.
authors: Nelly N
authors: NN
authors: Mateeva
authors: Shihab D
authors: SD
authors: Deiab
authors: Edikan E
authors: EE
authors: Archibong
authors: Mercedes
authors: M
authors: Jackson
authors: Bereket
authors: B
authors: Mochona
authors: Madhavi
authors: M
authors: Gangapuram
authors: Kinfe K
authors: KK
authors: Redda