dipicolinate

Dipicolinate is the dianion of dipicolinic acid, also known as pyridine-2,6-dicarboxylic acid. It forms when both carboxyl groups of dipicolinic acid are deprotonated, giving the ligand formula C7H3NO4 2-. The structure consists of a rigid pyridine ring with carboxylate groups at the 2- and 6-positions, enabling multidentate coordination to metal centers. In most coordination complexes, dipicolinate binds in a tridentate mode through the two carboxylate oxygens and the pyridine nitrogen, though bidentate coordination through the carboxylates alone is also common.

Natural occurrence and relevance: Dipicolinate is a key component in bacterial endospores. In many spores, calcium forms a complex with dipicolinate (calcium dipicolinate), which is a major constituent of the spore core and is thought to contribute to heat and dehydration resistance. In chemical contexts, dipicolinate is valued as a versatile ligand for studying metal–ligand interactions and for forming well-defined metal complexes.

Applications: In inorganic and bioinorganic chemistry, dipicolinate serves as a multidentate ligand for lanthanides and transition metals. Complexes with europium(III) or terbium(III) often exhibit characteristic luminescence due to energy transfer from the ligand, making dipicolinate-containing complexes useful in spectroscopic probes and time-resolved luminescence studies. The ligand also features in separation chemistry and supramolecular assembly where rigid, preorganized backbones promote stable, predictable coordination geometries.