Self-assembly of four one-dimensional molybdenum(V) phosphates linked by strontium and transition metal

Four reduced molybdenum(V) phosphates, [(py)2(Himi)4][FeII2SrMo12O24(OH)6(H2O)8(H2PO4)2(HPO4)4(PO4)2]·4H2O 1, (H2bpp)2[CoII2Sr2Mo12O24(OH)6(H2O)8(H2PO4)2(HPO4)2(PO4)4]·6H2O 2, [(Hpy)(Himi)][Ni(H2O)6][Ni2Sr2Mo12O24(OH)6(H2O)8(H2PO4)2(HPO4)2(PO4)4]·4H2O 3, (H2imi)2[Zn2Sr2Mo12O24(OH)6(H2O)6(H2PO4)2(HPO4)2(PO4)4]·3H2O 4 (imi = imidazole, bpp = 1,3-bi(4-pyridyl)-propane, py = pyridine), have been obtained by hydrothermal methods. These structures were determined by single-crystal X-ray diffraction analysis and were further characterized by elemental analysis, IR, and TG analysis. All the compounds contain the [P4Mo6O31]12− (abbreviated as [P4Mo6]) polyoxoanions as building blocks, which are further connected into the sandwich-type dimeric units by various transition metal (TM) ions. In compound 1, the dimeric {Fe[P4Mo6]2} units are bonded by an heterometallic {SrFe} binuclear unit to form 1-D string. In compounds 2–4, the dimeric {(TM)[P4Mo6]2} units are linked by new {Sr2TM} trinuclear fragments into one-dimensional (1-D) chains. All the 1-D chains are further packed into various three-dimensional (3-D) supramolecular assemblies via strong hydrogen-bonding interactions. Furthermore, the electrochemical activities of compounds 1–4 and magnetic properties of compounds 1–3 are reported.

Graphical abstractDifferent number of Strontium cation are introduced into the molybdenum(V) phosphates reaction systems for diverse reaction time, which lead to the assembly of four new poly(oxomolybdophosphates) based on sandwich-type building units {TM(P4Mo6)2} and {SrxTM} (x = 1,2) heterometallic linkers.Figure optionsDownload full-size imageDownload as PowerPoint slideHighlights► Different numbers of Sr2+ cation are introduced into the {P4Mo6} reaction systems. ► The reactive activity of Sr2+ cation is enhanced under short reaction time. ► 1–4-CPE displays unique redox properties. ► Magnetic properties of compounds 1–3 have also been investigated.