Metal complexes as templates: syntheses, structures, and luminescent properties of two zinc phosphonocarboxylates with ABW-zeolite topology

Abstract

Two novel zinc phosphonocarboxylates, Zn₃(pbc)₂(bpy)(H₂O)·H₂O (1) and Zn₂(pbc)₂·Zn(bpy)(H₂O)₄·2H₂O (2) (pbc = 4-phosphono-benzoic acid, bpy = 2,2′-bipyridine), were hydrothermally synthesized and structurally characterized. Both of them exhibit zeolitic ABW topology in which double-zigzag inorganic chains are cross-linked by the organic parts. It is notable that the metal complex Zn(bpy)(H₂O)_x plays different roles in the two compounds. In 1, the Zn(bpy)(H₂O) units coordinate with the phosphonate and carboxylate oxygen atoms and participate in the construction of the three-dimensional framework. In 2, the in situ generated [Zn(bpy)(H₂O)₄]²⁺ cation acts as a template, which directs the ABW-type open-framework by strong hydrogen bonds. It is the first example where a metal complex is used as a template in the synthesis of metal phosphonates. The luminescent properties of 1 and 2 are also investigated.