Nickel(II) com­plexes based on l-amino-acid-derived ligands: synthesis, characterization and study of the role of the supramolecular structure in carbon dioxide capture

The formation of the symmetrical μ(3)-carbonate-bridged self-assembled tri­nuclear Ni(II) com­plex Na(2){[Ni(LO)(2)(H(2)O)](3)(μ(3)-CO(3))} (LO is the carboxyl­ate anion of a l-tyrosine derivative), involves atmospheric CO(2) uptake. The asym­metric unit of the com­plex com­prises an octahedral coordination for the Ni(II) with two l-tyrosine-based ligands, a water molecule and one O atom of the carbonate bridge. The Ni(3)–μ(3)-CO(3) core in this com­pound is the first reported of this kind according to the Cambridge Structural Database (CSD). The supramolecular structure is mainly sustained by hydrogen bonds developed by the phenolic functionality of the l-tyrosine moiety of one ligand and the carboxyl­ate group of a neighbouring ligand. The crystal packing is then characterized by three interpenetrated supramolecular helices associated with a diastereoisomer of the type R-(sup) P, which is essential for the assembly process. Magnetic susceptibility and magnetization data support weak ferromagnetic exchange interactions within the novel Ni(3)–μ(3)-CO(3) core. The Ni(II) com­plex obtained under the same synthetic conditions but using the analogous ligand derived from the amino acid l-phenyl­alanine instead of l-tyrosine gives rise to to a mononuclear octahedral system. The results obtained for the different com­plexes demonstrate the role of the supramolecular structure regarding the CO(2) uptake property for these Ni(II)–amino-acid-based systems.