MOFs by Transformation of 1D-Coordination Polymers II: The Homoleptic Divalent Rare Earth 3D-Benzotriazolate 3∞[Eu(Btz)2] Initiating from 1∞[Eu(Btz)2(BtzH)2]

The solvent free reaction route produces coordination polymers that have a dimensionality of the linkage which is increasing with the thermal energy. The synthesis of the 3D MOF structure 3∞[Eu(Btz)2] marks the final thermal reaction step within the system europium/1H-1,2,3-benzotriazole. It can be obtained by a reaction of the metal with a melt of benzotriazole above 230 °C or from thermal treatment of the 1D coordination polymer 1∞[Eu(Btz)2(BtzH)2], Btz- = 1,2,3-benzotriazolate anion, C6H4N3–-, which is formed first at about 100 °C from the same reagents. In addition to the trivalent rare earth ions it can thus be shown that also divalent EuII together with benzotriazole exhibits transformation of a 1D coordination polymer into a 3D MOF. The homoleptic framework 3∞[Eu(Btz)2] exhibits a high thermal stability (525 °C) for an exothermically decomposing coordination compound. As 3∞[Eu(Btz)2] is always obtained as a microcrystalline product, structure solution and refinement were achieved by X-ray powder techniques. For further characterization 151Eu-Mößbauer, IR and Raman spectroscopy as well as micro and thermal analysis were carried out.