A PCT-based, pyrene-armed calix[4]crown fluoroionophore.
A photoinduced charge transfer (PCT)-based 1,3-alternate calix[4]crown fluoroionophore containing two cation recognition sites, a crown ether ring and two facing pyreneamide groups, is synthesized. Upon addition of K+, Pb2+, or Cu2+, wavelength changes are observed in both the fluorescence and absorption spectra, but with different binding modes. With K+, fluorescence emissions of the ligand scarcely change, while addition of Pb2+ or Cu2+ produces a remarkable change in both the excimer and monomer emissions. The observed data indicate that the metal cation is encapsulated in the crown-5 ring for K+ and by the two facing amide groups in the latter case, which is verified by a metal ion exchange experiment. The wavelength shifts in both fluorescence and absorption spectra upon addition of Cu2+ show that, in contrast to Pb2+, Cu2+ interacts with the nitrogen atoms of the amide groups, resulting in a PCT mechanism.
Choi
Jung Kyu
JK
Department of Chemistry, Institute of Nanosensor & Biotechnology, Dankook University, Seoul 140-714, Korea.
Kim
Su Ho
SH
Yoon
Juyoung
J
Lee
Keun-Hyeung
KH
Bartsch
Richard A
RA
Kim
Jong Seung
JS