Efficient route to hybrid polypyridine-carboxylate ligands for lanthanide complexation

An efficient methodology for the preparation of aminobutyl-bromo-terpyridine is described using a preformed imine prepared from a gem-dibromomethyl terpyridine derivative and the primary amine and further reduced to the secondary amine. Alkylation with pyridine, bipyridine, or terpyridine residues in the presence of a mineral base provides highly functionalized asymmetrical and symmetrical N-heterocyclic ligands. All bromo-containing products were subjected to a carboalkoxylation/hydrolysis sequence of reactions, providing the desired carboxylic acids. Stable Eu complexes were prepared under neutral aqueous conditions and some of them display interesting spectroscopic properties.