New Sensitizer-Modified Calix[4]arenes Enabling Near-UV Excitation of Complexed Luminescent Lanthanide Ions

The synthesis is described of a series of calix[4]arenes with three different sensitizer chromophores ('antenna') attached to the lower rim via a short spacer. In the Eu super(3+) and Tb super(3+) complexes of these calixarenes, photoexcitation of the antenna can induce lanthanide emission via intramolecular energy transfer. Although the higher energy of the Tb super(3+) luminescent state makes it more difficult to sensitize than in the case of Eu super(3+), especially a triphenylene antenna is found to have strong sensitizing ability toward not only Eu super(3+) but also Tb super(3+), allowing excitation of the lanthanide with wavelengths extending to 350 nm.