Abstract
Using tri-ethyl phosphate as a phosphate source, the hydrothermal reaction of cobalt(II) oxalate di-hydrate, zinc oxide and 1,8 di-amino octane at 200°C gave purple crystals of Co6(PO4)4 · 7H2O (1), along with a mixture of open-framework zinc–cobalt phosphates Co–Zn–HPO4, and Co3(HPO4)2(2OH). Compound 1, has been characterized by thermal analysis, FTIR and single crystal X-ray diffraction. The single crystal structure of Co6(PO4)4 · 7H2O reveals cobalt in four, five and six-fold coordination with linkages through the bridging water molecules and the oxygen atoms of the phosphate in the subunits. Four subunits are connected together through the oxygen atoms (PO4), to form the three dimensional open framework structure, with a 20-member ring channel that hosts two uncoordinated water molecules. Thermal removal of the water molecules occurs between 400–600°C, with the collapse of the structure above 600°C.
Acknowledgments
The authors acknowledge support from the Welch Foundation, NSF supported Center for Environmental Beneficial Catalysis, CEBC (funding #EEC 0310689). This work made use of the Cornell Center for Materials Research Facilities supported by the National Science Foundation under Award number DMR-0520404, and the single crystal diffractometer was funded by NSF grant 0087210, by Ohio Board of Regents grant CAP-491, and by YSU.