Two rare {M 2 (MoO 4 ) 2 } n chain-containing molybdate-based metal-organic complexes with a bis-pyrazole-bis-amide ligand: fluorescent sensing and photocatalysis performance.

By introducing a bis-pyrazole-bis-amide ligand, N , N '-bis(1 H -pyrazole-4-carboxamide)-1,4-benzene (L), two molybdate-based metal-organic complexes containing {M 2 (MoO 4 ) 2 } n (M = Co, Zn), [Co 2 L 2 (MoO 4 ) 2 ]·H 2 O (1), [Zn 2 L 2 (MoO 4 ) 2 ]·H 2 O (2), have been prepared under hydrothermal/solvothermal conditions. X-ray diffraction analyses reveal that both 1 and 2 are isostructural. An interesting structural feature is that a kind of {M 2 (MoO 4 ) 2 } n chain could be found in 1 and 2, although different raw materials [Mo 7 O 24 ] 6- and [PMo 12 O 40 ] 3- anions were utilized. Then these chains are further linked by L ligands into a two dimensional (2D) structure. The title complexes represent the first examples containing {MoO 4 } units and pyrazole-/or amide-derivative ligands. Complexes 1 and 2 exhibit distinct performances due to different metal centers, with 2 acting as a fluorescent sensor for Fe 3+ , MnO 4 - , CrO 4 2- and Cr 2 O 7 2- , but 1 being a better photocatalyst towards degradation of cationic dyes methylene blue (MB) and neutral red (NR).