A process is provided herein for preparing molecularly imprinted polymers for detecting a target analyte by Reversible Addition Fragmentation Chain Transfer (RAFT). The process includes providing a complex having the formula L.sub.3M wherein L is a .beta.-diketone ligand containing a chain transfer moiety and L.sub.3 can be the same or different ligands, and M is a lanthanide element; reacting the complex with the target analyte to provide an adduct containing the target analyte; co-polymerizing the adduct with a monomer and cross-linking agent to provide a polymer; and removing the target analyte from the polymer to provide the molecularly imprinted polymer.