Effect of N-donor ancillary ligand on zinc/cadmium-organic arsonates: Structural analysis and photoluminescence

Abstract

The design and construction of metal organic frameworks (MOFs) or coordination polymers (CPs) with tunable structures is of great interest in recent years, owing to their intriguing structural diversity and potential applications. The mixed-ligand approach is widely used as an effective synthesis method to fabricate CPs. By precise regulation of the structure of N-donor co-ligands, in this work, a series of zinc/cadmium-organic arsonates are successfully synthesized, namely, [Zn2(OH)(L-As)(4,4′-Bipy)⋅H2O]n (1), [Zn3(L-As)2(2,2′-Bipy)(H2O)2⋅2H2O]n (2), [Cd(HL-As)(4,4′-Bipy)0.5]n (3), [Cd(HL-As)(2,2′-Bipy)(H2O)⋅H2O]n (4) (H3L-As ​= ​2-(carboxymethylamino)phenylarsonic acid; 4,4′-Bipy ​= ​4,4′-bipyridine; 2,2′-Bipy ​= ​2,2′-bipyridine). We demonstrate that N-donor co-ligands significantly affect the coordination environment of metal centers and the structure of these compounds. Compound 1 is a three-dimension (3D) hydrogen-bond network via C–H···π interactions between the aromatic rings of L-As ligand, whereas 3 exhibits a 3D framework with 6-connected pcu topological network. By contrast, 2 and 4 are two-dimension (2D) layered structures by adopting chelated 2,2′-Bipy Co-ligand. All compounds display a luminescence from ligand-to-metal charge transfer (LMCT) which depends on the coordination environment of metal centers. The results show that N-donor co-ligands can effectively regulate the structures and luminescent properties of the formed CPs.