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Synthetic route influence on the formation of supramolecular Co(III)-Mo(VI) double- complex salts

The employment of different transition metal complexes and organic components along with polyoxometalates in the targeted synthesis and design of novel supramolecular materials having potential applications in the fields of heterogeneous catalysis and magnetism is of current trend in synthetic chemistry. The self- assembly of this inorganic-organic polyoxometalate based hybrids and their crystals formation is predominantly achived by interplay of hydrogen bonding and electrostatic interactions. Our investigation of the reactions between discrete anionic polyoxomolybdates and cationic tris(ethylenediamine)cobalt(III) complex, in the presence of malonic acid, resulted in a series of supramolecular Co(III)-Mo(VI) double- complex salts [Co(en)3]2[NaMo7O24]Cl·9H2O, (H3O) [Co(en)3]2[Mo7O24]Cl·4H2O, [Co(en)3]2[Mo7O24]·5H2O and [Co(en)3]4[Mo22O73]·10H2O (en = ethylenediamine). In order to explore the influenece of the synthetic route on the formation of examined double-complex salts of Co(III) and Mo(VI), their synthesis was performed via both conventional solution-based methods (under room temperature or hydrothermal conditions), liquid assisted mechanochemical grinding (LAG) and aging. To investigate the influence of the nuclearity of starting anionic polyoxomolybdates and role of malonic acid in these reactions, [Co(en)3]3+ macrocation was probed with [MoO4]2–, [Mo6O19]2–, [Mo7O24]6– and [Mo8O26]4– in the presence and without malonic acid. All compounds were charactrized by means of infrared spectroscopy, thermal analysis and X-ray diffraction.

solution-based synthesis ; liquid-assisted grinding ; cobalt polyoxomolybdates

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