New Types of Layered and Pillared Layered Metal Carboxylate-Phosphonates Based on the 4,4‘-Bipyridine Ligand

Hydrothermal reactions of transition metal salts with HO₂CCH₂N(CH₂PO₃H₂)₂ (H₅L) and 4,4‘-bipyridine (bipy) lead to two new metal carboxylate-diphosphonates, namely, Co₃(H₂L)₂(H₂O)₄(bipy)₂·11H₂O (1) with a layered structure, and a blue luminescent compound, Zn₅L₂(bipy)₂·9H₂O (2) with a pillared layered structure. In compound 1, three Co(II) ions are interconnected by two chelating and bridging phosphonate ligands to form a trinuclear unit, and such units are further cross-linked via bridging bipy ligands to form a 2D layer. In compound 2, the zinc(II) ions in the trigonal bipyramidal or tetrahedral geometries are interconnected via chelating and bridging carboxylate-phosphonate ligands into 2D layers which are further cross-linked by 4,4‘-bipy ligands into a pillared layered architecture. Results of luminescent studies indicate that compound 2 is a blue light luminescent material.