engleski

From [Mo7O24]2- to Anderson-type anion [CoII(OH)6Mo6O18]4− in presence of [Co(ox)(NH3)4](NO3) and under hydrothermal conditions

The self-assembly processes and different type of interactions of [MoO4]2- anions, along with their transformation to higher species, have been identified as the main driving forces responsible for the formation of polyoxomolybdates (POMos). The syntheses of these discrete anionic metal oxygen clusters are examples of modern crystal engineering. The main challenge behind practical crystal engineering is the fact that properties and performance of solid materials can be controlled by specific features of the molecules or ions that make up a particular material. In our previous works1 we have postulated that the reaction conditions and hydrogen bonding capacity of counter ions are the most important factors that induce the diverse polyoxalatooxomolybdate anions during the selfassembly process of {; ; ; MoO4}; ; ; units. We have also successfully applied for the first time liquid-assisted ball milling followed by vapour-assisted aging for the synthesis of POMos.2 This mechanochemical approach has enabled us the identification of reaction intermediates, coordination polymer with {; ; ; NaMo7O24}; ; ; and heptamolybdate {; ; ; Mo7O24}; ; ; unit, respectivelly, as the primary condensation products of [MoO4]2− anions into the {; ; ; Mo7O24(μ-Mo8O26) Mo7O24}; ; ; in the presence of [Co(en)3]3+ counterion.2 These results stimulated us to explore hydrothermal reactions of K2[MoO3(C2O4)]·H2O, [(n-C4H9)4N]2[Mo6O19], [(n-C4H9)4N]4[Mo8O26] or (NH4)6[Mo7O24]·4H2O with [Co(C2O4)(NH3)4](NO3) at pH = 5−6, yielded four new compounds having different nuclearity and composition: [CoIII(C2O4)(NH3)4]3[(NH3)4CoIIIC2O4CoII(H2O)4][Mo7O24], [CoIII(C2O4)(NH3)4]2[MoO4]·H2O, [CoIII(C2O4) (NH3)4]3(NH4)[CoIIMo6(OH)6O18]·6H2O, [CoIII(C2O4)(NH3)4]6[Mo7O24]·6H2O and two polymorphic form of [CoIIIC2O4(NH3)4]2[CoII(C2O4)2(H2O)2]·4H2O.

self-assembly ; polyoxomolybdates ; mechanochemistry ; hydrothermal synthesis

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