Lanthanide-Organic Framework of a Rigid Bis-Gd Complex: Composed by Carbonate Ions Spacers

A new lanthanide-organic framework (LOF) based on a long (21.2 angstrom) and rigid bis-Gd complex synthon (complex 1) and carbonate anion spacers was discovered. Complex 1 is comprised of two Gd3+ ions complexed with a pyridine tetracarboxylate ligand and a bridging linear 1,4-diethynylbenzene unit. Two water molecules are coordinated to each Gd ion in order to satisfy its high coordination number. Upon crystallization of 1 in ethanolic aqueous sodium bicarbonate, the carbonate anions replace the coordinated water molecules, partially or fully, resulting in the construction of two network types (type A and B). All three oxygen atoms of the carbonate anion are utilized in its function as a spacer between two synthons (complex 1) in the networks, but the chelating oxygen atoms (to Gd3+ ions) and their coordination modes differ in each or the two networks. In addition, the carbonate anions also serve as acceptors for hydrogen bonding (O H center dot center dot center dot O) with water molecules coordinated to Gd3+ ions in both the net works. While all the synthons adopt a planar conformation in network A. they tire backed alternatingly in plane and vertical conformation in network B. Overall, in this new LOF the synthons are packed in ens-cross fashion and tethered by carbonate ion spacers, creating a crystal lattice perforated by 10.6 x 15.6 angstrom and 18.6 x 15.6 angstrom wide-open channels.