ja045689c_si_001.pdf (263.74 kB)
An Excimer-Based, Binuclear, On−Off Switchable Calix[4]crown Chemosensor
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 KimA 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.