Assembling [M(P4Mo6)2] (M = Na, Mn, Na/Cu) dimeric clusters via transition metal/sodium ions into 0D to 3D phosphomolybdates

Six phosphomolybdate compounds based on the sandwich-type cluster [M(P4Mo6X31)2] (M = Na, Mn, Na/Cu; X = O or OH) have been solvothermally synthesized by using various organic/inorganic cations as templates, namely, (H3AEP)4[Na(P4Mo6O31H5.5)2]·4H2O (1), (Me2NH2)7[NaMn(H2O)][Mn(P4Mo6O31H6)2]·5H2O (2), (H4tpc)0.5(H4tpb)0.5(H0.5bpp)[Na2.5(H2O)][Na(P4Mo6O31H8)2]·2H2O (3), (Me2NH2)6.5[Na4(H2O)8][Cu0.25Na0.75(P4Mo6O31H6.25)2] (4), (Me2NH2)1.5(NH4)4[Mn1.5Na4.5(H2O)7][Mn(P4Mo6O31H4.5)2]·3.5H2O (5), and (DMIm)4[Mn1.5Na2(H2O)8][Mn(P4Mo6O31H6.5)2]·1.5H2O (6) (AEP = 1-(2-aminoethyl) piperazine, Me2NH = dimethylamine, bpp = 1,3-bis(4-pyridyl)propane, tpb = 1,2,4,5-tetra(4-pyridyl)-benzene, tpc = a,a-1,4-dihydroxy-e,e,e,e-1,2,4,5-tetra-(4-pyridyl)cyclohexane, and [DMIm] = 1,3-dimethylimidazolium). These compounds were characterized by elemental analysis, PXRD, IR, TGA, and single-crystal X-ray diffraction. Compound 1 features a classical zero-dimensional (0D) dimeric cluster [Na(P4Mo6O31H5.5)2]. Compound 2 possesses a 1-D chain constructed from the linkage of [Mn(P4Mo6O31H6)2] dimeric clusters and M (M = Na+, Mn2+) linking metal ions. Compounds 3 and 4 are characteristic of 2-D layers, which are built up by connecting [Na(Mo6P4O31H8)2] and [M(Mo6P4O31H6.5)2] (M = Cu0.25/Na0.75) dimeric clusters, respectively, via Na+ ions. Compounds 5 and 6 feature 3D frameworks, where the dimeric clusters are interconnected by M (M = Na+, Mn2+) ions. Thus, the application of linking metal ions with different coordination modes and valence states to assemble [M(P4Mo6X31)2] clusters is promising for harvesting new phosphomolybdates. In particular, compounds 1 and 5 exhibited visible light degradation performance for Rhodamine B.