Supramolecular cooperative interaction-induced assembly of phosphotungstate polyanions and sulfur-containing pyridine-based cations

Three new polyoxometalate (POM) supramolecular assemblies constructed from phosphotungstate clusters and S-containing pyridine-based cations had been successfully isolated and characterized. Structural analysis revealed that their formula were (H 2 PySSPy) 3 [PW 12 O 40 ] 2 ·6H 2 O ( 1 ), (H 3/2 PySPy) 2 [PW 12 O 40 ]·6H 2 O ( 2 ) and [Ag(HPyS)] 4 [Ag 8 (H 2 O) 9 ][P 2 W 18 O 62 ] 2 ·4H 2 O ( 3 ) (PySSPy = 4,4′-dipyridine disulfide; PySPy = 4,4′-thiodipyridine; PySH = pyridine-4-thiol), respectively. The three crystals were assembled by means of multiple weak intermolecular cooperative interactions of hydrogen bonding, S⋯O, C–H⋯π, etc. In particular, the peculiar supramolecular bond of the ‘polyanion–π’ binding interaction between the polyanion receptor and the six-membered pyridine ring was described in some detail. These complex and noncovalent contacts efficiently induce the construction of the crystal supramolecular lattices of 1–3 . During the formation process of 2 and 3 , organic moieties were achieved through the in situ cleavage of S–S chemical bonds in PySSPy. Crystal 3 contains a 3D network constructed from Dawson-like polyanions and Ag–PyS cationic units through Ag–O and Ag–S coordination bonds. One anionic [P 2 W 18 O 62 ] 6− cluster is bonded to eighteen Ag ions through many Ag–O interactions, presenting an interesting Ag 18 -supported Dawson structure.