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Stepwise mechanism and the effect of the liquid phase in the liquid-assisted grinding synthesis of metal-organic materials

The role of water in the room-temperature liquid-assisted grinding (LAG) synthesis of a model coordination polymer from ZnO was investigated, and the scope of the synthetic methodology was expanded to copper compounds by using water as a catalyst in the construction of copper(II) acetate monohydrate from CuO and acetic acid. The mechanochemical syntheses of model compounds zinc fumarate and of copper(II) acetate proceed via a similar stepwise reaction mechanism which involves the intermediate formation of solvates with water (in case of zinc fumarate) or acetic acid (in case of copper(II) acetate) as kinetic products. The course of zinc fumarate LAG synthesis has been explored using three different types of grinding liquids: water, aqueous mixtures of organic solvents and pure organic solvents. With liquid water, the formation of the kinetic product switches the reaction mechanism from LAG to a neat grinding process. As a result, the scope of products becomes limited to anydrous zinc fumarate and either the tetrahydrate or the pentahydrate forms. A significant qualitative difference is seen between LAG reactions involving aqueous solutions of different liquids, and as a first step towards the quantitative understanding of how the liquid phase affects mechanosynthesis, we demonstrate that the difference can be correlated with the mole fraction of water.

liquid assisted grinding ; stepwise rection mechanism ; water effects

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