Influence of upper rim dibromo-substitution in bis-1,3-diketone calix[4]arenes on spectral properties of ligands and their lanthanide complexes

New bis-1,3-diketone calix[4]arene derivatives adopting cone conformation with dibromo-substituted upper rim of calix[4]arene backbone are introduced as ligands for lanthanide ions with improved sensitization of Tb3+-centered luminescence due to heavy-atom effect.177