Role of supramolecular interactions in crystal packing of Strandberg-type cluster-based hybrid solids

Two new Strandberg-type cluster-based phosphomolybdates {H-2a3mp}₅[{PO₃(OH)}{PO₄}Mo₅O₁₅], 1 and {H-2a4mp}₅[{PO₃(OH)}{PO₄}Mo₅O₁₅]·6H₂O, 2 have been crystallized via solvent evaporation technique using 2-amino-3-methylpyridine (2a3mp) and 2-amino-4-methylpyridine (2a4mp) respectively. The solids were characterized using single-crystal X-ray diffraction, powder X-ray diffraction, fourier transform infrared spectroscopy, thermogravimetric analysis, scanning electron microscopy and cyclic voltammetry. The solid 1 crystallized in monoclinic system with space group P2₁/c, a = 8.394(1), b = 27.398(6), c = 21.521(4) Å, β = 97.68(3)°, Z = 4. The solid 2 crystallized in triclinic system with space group P-1, a = 11.728(1), b = 14.234(1), c = 19.589(1) Å, α = 68.906(3), β = 89.454(3), γ = 66.559(3)°, Z = 2. The solids 1 and 2 formed a supramolecular framework stabilized by hydrogen bonding interaction between cluster anions and organic moieties. CH…π interactions between the organic moieties reinforced the crystal packing in 1 and 2. While crystal packing effects resulted in the formation of solvent-accessible voids in 1; aggregation of lattice water molecules in 2 facilitated the formation of pentameric water cluster. In addition, electrochemical behavior of 1 and 2 has also been investigated.

Graphic abstract

Two new Strandberg-type cluster based phosphomolybdates, 1 and 2 have been crystallized via solvent evaporation technique using 2-amino-3-methylpyridine and 2-amino-4-methylpyridine. Detailed structural analysis revealed the role of supramolecular interactions in the crystal packing of these solids. In addition, electrochemical behavior of 1 and 2 has also been investigated.