New Series of Oxalato-Gallophosphate Structures Containing Transition Metal Centers

Department of Chemistry, National Tsing-Hua University
○Wen-Ming Chang Sue-Lein Wang

The synthesis of organic-inorganic hybrid materials by incorporating appropriate organic ligands into the inorganic frameworks has been the subject of intense research. One class of organic-inorganic hybrid frameworks is based on oxalate and phosphate in which the metal centers are coordinated by two types of ligands. In the search for new varieties of frameworks, we further incorporate transition metals into the oxalato- gallophosphate structures. Along this line, five novel organic-inorganic hybrid mixed-metal oxalatophosphates, (C3H12N2)2[(VO)2(ox)Ga2(PO4)4](1), (C10H28N4)[(VO)2(ox)Ga2(PO4)4].2H2O(2), (C7H21N3)0.5(H3O)[Mn(H2O)2Ga4F2(ox)(PO4)4].4H2O(3), (C5H14N2)[Mn(H2O)2Ga4F2(ox)(PO4)4].3H2O(4) and (C4H16N3)[MnGa2(ox)2(HPO4)2(PO4)](5) (ox = C2O42-) were successfully synthesized under mild hydrothermal conditions. They were characterized by single-crystal X-ray diffraction, magnetic susceptibility and TG analysis. The vanadium compounds 1 and 2 are layered whereas the manganese compounds 3, 4, and 5 are 3D materials. The oxalate anion can act as a bis-bidentate ligand in all five compounds and also as a mono-bidentate ligand in 5. Besides homo bi-octahedral units of M'2(ox)O6 (M' = (VO) for 1 and 2, (GaF) for 3 and 4), we observe the first hetero chelating MnGa(ox)O8 unit, formed of an unusual Mn[6p]O6 trigonal prism and a GaO6 octahedron, and unique trimeric polyhedral Mn(H2O)2(GaF)2O12 and MnGa2O16 units. The fundamental frameworks for 1-5 effectively display a series that are constructed from a substructure of 1D or 2D with a four ring linker and/or Mn2+ ions into 2D or 3D structures. The hetero metals have imposed magnetic property to the Ga(ox)PO lattices and led to the first well-defined M-X-Ga (X = O, F) bonds ever observed in the metal phosphate chemistry.