Functionalized Phosphonated Half-Cage Molecules as Ligands for Metal Complexes

Phosphonated molecules, featuring a half-cage structure and a N-lateral chain with additional metal coordinating groups were designed as ligands of metal cations. These compounds were synthesized by a Diels-Alder (DA) strategy, using 1-diethoxyphosphoryl-1,3-butadiene and a series of N-substituted maleimides as dienophiles. Two cycloadducts, bearing a terminal primary alcohol and a terminal iodide, respectively, were used as key intermediates for further functionalizations. Metal coordination properties of the ligands equipped with functionalized N-lateral chains were proven by an ESI-HRMS study. The stoichiometry of one selected Eu III complex with a diphosphonated ligand was determined by photoluminescence spectroscopy in emission mode