Two novel organic–inorganic hybrid molybdenum(v) cobalt/nickel phosphate compounds based on isolated nanosized Mo/Co(Ni)/P cluster wheels

Abstract

Two high-nuclear wheel-shaped nanoscale clusters, [Co(H₂O)₆]{[C₃H₄N₂]₂[C₅NH₅]₁₄[H₁₅(Mo₂O₄)₈Co₁₆(PO₄)₁₄(HPO₃)₁₀(OH)₃]}·5H₂O (1) and [C₃H₅N₂]₄[C₅NH₅]₂[Ni(H₂O)₆]{[C₃H₄N₂]₂[C₅NH₅]₁₄[H₁₈(Mo₂O₄)₈Ni₁₆(PO₄)₂₂(OH)₆]}·11H₂O (2), have been successfully synthesized employing the Py and Imi ligands as chemical modifiers. Both clusters take nanoscale wheel-like shapes, and the inorganic cores are wrapped up by the Py and Imi ligands acting as organic shells. In compounds 1 and 2, the polyoxoanion unit exhibits a new organic–inorganic hybrid polymolybdophosphate, representing the first two isolated POMs in the wheel-type {Mo/TM/P} materials, while Py and Imi ligands improve electric the delocalization effects of polyanions. It is worth noting that the molecular TPA cross section σ of compound 1 is 2.5 times that of compound 2, which demonstrates that the nonlinear optical property can also be improved by replacing part of the phosphate radicals with phosphite radicals through enhancing electron delocalization.