engleski

Mechanochemical synthesis and crystal structure of new group of mixed–metal imidazolates AMgIm3

Mechanochemical synthesis was used for preparation of first bimetallic imidazolates containing alkali and alkaline earth metals, NaMgIm3 and KMgIm3. Preparation of NaMgIm3 has been done by reaction between NaIm and Mg(BH4)2 as well as directly from NaIm and MgIm2. Literature shows that alkali imidazolates (NaIm, Kim and LiIm) form the dense and hypercoordinated structures where the coordinative demand of the metal cation increases with an increase of the ionic radii. On the other hand, porous zeolitic imidazolate framework, MgIm2, is formed by the utilization of an alkali earth metal. [1, 2] In-situ high temperature XRPD experiment utilizing the synchrotron radiation was used for structural evolution and thermal stability. In both compounds, the imidazolate ligand is connected to four metal cations forming a complex 3D network with channels running along the c- direction. Unlike mono cation imidazolates (NaIm and MgIm2) which show tetrahedral coordination of metals [1], in NaMgIm3 each Na and Mg cation is exhibiting distorted octahedral coordination. NaMgIm3 and KMgIm3 are first members of new family of imidazolate frameworks with stp topology. Formation of mixed alkali metal imidazole compounds is under thermodynamical control ; reaction between LiIm and MgIm2 have not yielded a mixed-metal compound while KIm reacts swiftly and forms KMgIm3.

mechanochemical synthesis ; tetrahydridoborates ; hybrid metal-organic frameworks ; imidazolate ; X-ray powder diffraction ; synchrotron radiation ; crystal structure determination

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