Two
N-pyrenylacetamide-substituted sugar-aza-crown ethers have been synthesized as new fluorescentchemosensors. The designed ligands
1 and
2 exhibit fluorescence characteristics of a pyrene monomerand a dynamic excimer emission when compared to
N-pyrenylacetamide as a model compound. Bothligands displayed a Cu
2+-sensitive fluorescence quenching with a 1:1 stoichiometry and high stabilityconstants (log
K = 6.7 for
1 and 7.8 for
2). The quenching effect was rationalized on the basis ofphotoinduced electron transfer from the excited pyrene to the complexed Cu
2+ cation, while the changesin excimer-to-monomer ratio were explained by a conformational analysis through DFT calculations.The predicted structure suggests that the Cu
2+ cation is coordinated with the two carbonyl groups andthe sugar-aza-crown ethers which rigidified the complex structure and placed the two pyrene moietiesfar apart.
