Metal ion complexation in acetonitrile by di-ionized calix[4]arenes bearing two dansyl fluorophores |
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Authors: | Ümmühan Ocak Miraç Ocak Kazimierz Surowiec Richard A Bartsch Maryna G Gorbunova Chuqiao Tu Malgorzata A Surowiec |
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Institution: | 1. Department of Chemistry and Biochemistry, Texas Tech University, Lubbock, TX, 79409, USA 2. Department of Chemistry, Faculty of Arts and Sciences, Karadeniz Technical University, 61080, Trabzon, Turkey
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Abstract: | The influence of metal cations (Li+, Na+, K+, Rb+, Cs+, Mg2+, Ca2+, Sr2+, Ba2+, Ag+, Cd2+, Co2+, Fe2+, Hg2+, Mn2+, Pb2+, Zn2+ and Fe3+) on the spectroscopic properties of two dansyl (1-dimethylaminonaphthalene-5-sulfonyl) groups linked to the lower rims of a series of three, structurally related, di-ionized calix4]arenes was investigated by means of absorption and emission spectrophotometry. Di(tetramethylammonium) salts of the di-ionized ligands, (TMA)2L1, (TMA)2L2 and (TMA)2L3, which differ in having zero, two and four tert-butyl groups, respectively, on the upper rim of the calix4]arene scaffold were utilized for the spectrofluorimetric titration experiments in acetonitrile. On complexation by alkaline earth metal cations, both the absorption and emission spectra undergo marked red shifts and quenching of the dansyl fluorescence. These effects are weaker with alkali metal cations. Transition metal cations interact strongly with the ligands. In particular, Fe3+, Hg2+ and Pb2+ cause greater than 97% quenching of the dansyl fluorescence in the di-ionized ligands. |
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