1,3-Alternate calix[4]arene-based fluorescent chemosensors bearing two-photon absorbing chromophoreshave been synthesized, and their sensing behaviors toward metal ions were investigated via absorptionband shifts as well as one- and two-photon fluorescence changes. Free ligands absorb the light at 461 nmand weakly emit their fluorescence at 600 nm when excited by UV-vis radiation at 461 nm, but notwo-photon excited fluorescence is emitted by excitation at 780 nm. Addition of an Al
3+ or Pb
2+ ion toa solution of the ligand causes a blue-shifted absorption and enhanced fluorescence due to a declinedresonance energy transfer (RET) upon excitation by one- and two-photon processes. Addition of a Pb
2+ion to a solution of
1·K
+ results in a higher fluorescence intensity than the original
1·Pb
2+ complexregardless of one- or two-photon excitation, due to the allosteric effect induced by the complexation ofK
+ with a crown loop.
