Using a flexible bis(pyrazol) ligand to construct four new Keggin-based compounds: syntheses, structures and properties

Using a flexible bis(pyrazol) ligand, four new compounds based on Keggin anions, namely [Cu(H 2 bdpm) 2 (H 2 O) 2 (HPW 12 O 40 )] ( 1 ), [Cu(H 2 bdpm) 2 (H 2 PW 12 O 40 )] 2 ·2H 2 O ( 2 ), [Cu 2 (H 2 bdpm) 3 (H 2 O) 2 (SiW 12 O 40 )]·2H 2 O ( 3 ), and [Cu 2 (H 2 bdpm) 4 (H 2 O) (SiW 12 O 40 )]·16H 2 O ( 4 ) (H 2 bdpm = bis(3,5-dimethyl-1 H -pyrazol-4-yl)methane), have been synthesized under hydrothermal conditions. Compound 1 is a zero dimension (0D) structure, showing a [Cu(H 2 bdpm) 2 ] 2+ mono-supporting [PW 12 O 40 ] 3− anion. Compound 2 shows a 1D supramolecular chain, with bi-supporting anions lined by discrete [PW 12 O 40 ] 3− anions. Compound 3 contains bi-nuclear Cu 2+ cycles, which are linked by O4W to form a cycle-connecting-cycle chain. The [SiW 12 O 40 ] 4− anions connect adjacent chains to construct a 2D structure. Compound 4 contains a nested cycle subunit [Cu 4 (H 2 bdpm) 6 ] 8+ , with two bi-nuclear cycles [Cu 2 (H 2 bdpm) 2 ] 4+ linked by two H 2 bdpm ligands. The nested cycle subunits are connected by H 2 bdpm molecules to construct a 2D metal–organic layer. The Keggin anions link adjacent layers to form a 3D framework. The electrochemical and photocatalytic properties of compounds 1–4 are studied.