Directing role of the synthetic route on the self-assembly process of MoO42− units to Mo7O242− or Mo22O7416− ions

Different synthetic routes, solution-based methods performed at room temperature, under reflux or hydrothermally at 110 °C, along with mechanochemically accelerated (hand grinding or liquid-assisted ball milling) vapour-assisted aging, yielded polyoxomolybdate [Co(en)3]2[Mo7O24]·8H2O (1) as the final product. The new heptamolybdate 1 was the only product of the reaction between sodium molybdate, tris(ethylendiamine)cobalt(III) chloride and succinic acid when the used molar ratio of Mo: Co: acid was 1:1:1 or 1:6:1, regardless to the employed synthetic route (solution vs. solid state). From the literature known polyoxomolybdate [Co(en)3]5Na[Mo7O24(μ-Mo8O26)Mo7O24]·nH2O (2) was also isolated as the main product only from the solution based methods where the sodium molybdate was present in an excess (molar ratio 6:1:1) and in the case when the reaction was conducted at elevated temperature and by employing the excess of succinic acid (molar ratio 1:1:6). All products were characterized by means of elemental analysis, IR spectroscopy as well as powder and single crystal X-ray diffraction analysis.