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An Excimer-Based, Binuclear, On−Off Switchable Calix[4]crown Chemosensor

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journal contribution
posted on 2004-12-22, 00:00 authored by Sung Kuk Kim, Seoung Ho Lee, Ji Yeon Lee, Jin Yong Lee, Richard A. Bartsch, Jong Seung Kim
A new fluorescent chemosensor with two different types of cation binding sites on the lower rims of a 1,3-alternate calix[4]arene (1) is synthesized. Two pyrene moieties linked to a cation recognition unit composed of two amide groups form a strong excimer in solution. For 1, the excimer fluorescence is quenched by Pb2+, but revived by addition of K+ to the Pb2+ ligand complex. Thus, metal ion exchange produces an on−off switchable, fluorescent chemosensor. Computational results show that the highest occupied molecular orbital (HOMO) and the lowest unoccupied molecular orbitals (LUMO) of the two pyrene moieties interact under UV irradiation of 1 and its K+ complex, while such HOMO−LUMO interactions are absent in the Pb2+ complex.

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