Metal ion complexation in acetonitrile by cone,di-ionised calix[4]arene-1,2-crown ethers with two pendant dansyl fluorophores |
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Authors: | Ümmühan Ocak Miraç Ocak Chuqiao Tu Richard A. Bartsch |
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Affiliation: | 1. Department of Chemistry , Faculty of Arts and Sciences, Karadeniz Technical University , 61080, Trabzon, Turkey uocak@ktu.edu.tr;3. Department of Chemistry , Faculty of Arts and Sciences, Karadeniz Technical University , 61080, Trabzon, Turkey;4. Department of Chemistry and Biochemistry , Texas Tech University , Lubbock, TX, 79409, USA |
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Abstract: | Four cone calix[4]arene-1,2-crown ethers each with two ionisable side arms containing dansyl groups are synthesised. The crown ether ring on the lower rim is varied from crown-4 to crown-5 with hydrogen or tert-butyl groups on the para position of the upper rim. Di(tetramethylammonium) salts of the di-ionised ligands are utilised for spectrofluorimetric titration experiments in MeCN. The influence of alkali metal, alkaline earth metal and selected transition and heavy metal (Co2+, Fe2+, Hg2+, Mn2+, Pb2+, Zn2+ and Fe3+) cations on the spectroscopic properties of the two dansyl groups linked to the lower rim of the conformationally locked, di-ionised calix[4]arene-1,2-crown ether frameworks is investigated by emission spectrophotometry. All of the metal cations induce red shifts in the emission spectra of the di-ionised ligands. The metal cations produce enhancement or quenching of the fluorescence emissions. Changes in the fluorescence emission as a function of the metal cation identity, the lower rim crown ether ring size and the absence or presence of upper rim tert-butyl groups are investigated. |
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Keywords: | calixarene-crown ether ligand fluorescence spectroscopy stability constant metal ion complexation |
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