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

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.