The hydrothermal synthesis of transition metal complex templated octamolybdates

Katikaneani Pavani, Samuel E. Lofland, Kandalam V. Ramanujachary, Arunachalam Ramanan

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Abstract

The hydrothermal reaction of an aqueous ammonium heptamolybdate solution with cobalt or copper metal salts in the presence of imidazole (imi) or pyrazole (pz) in the temperature range 120-180°C and at autogenous pressure yields four fully oxidized metal-complex-templated octamolybdates, namely [{Cu 1(imi)2}4(imi)2Mo8O 26]·4H2O (1), (Himi)2-[{Cu II(imi)2}2Mo8O27] (2), [{CoII(pz)4}2(pz)2Mo 8O26] (3), and [{CuII(pz)4} 2Mo8O26]·2H2O (4). The single-phase nature of the solids was established by single-crystal and powder X-ray diffraction, thermal analysis, and spectroscopic techniques. Compounds 1, 3, and 4 are neutral composite solids - 1 is a discrete molecular unit while 3 and 4 are 2D sheets. Compound 2 consists of anionic chains with imidazolium counter cations. The influence of the metal complex and temperature of the hydrothermal reaction on the formation of the different hybrid solids built of octamolybdate clusters is discussed. We also provide plausible mechanisms for the self-assembly of the crystals in terms of supramolecular organization between metal complexes and soluble molybdenum precursors in the initial stages of the reaction. The magnetic properties of 2, 3, and 4 confirm the presence of Cu and Co in the divalent state with no appreciable long-range order down to 5 K, whereas 1 is diamagnetic.

Original languageEnglish (US)
Pages (from-to)568-578
Number of pages11
JournalEuropean Journal of Inorganic Chemistry
Issue number4
DOIs
StatePublished - Jul 2 2007

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All Science Journal Classification (ASJC) codes

  • Inorganic Chemistry

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