Ln‐Imidazolate Frameworks: The Coordinative Demand of Ln3+ Ions and its Consequences for the Compound Constitution of Different Lanthanides

Abstract

AbstractBy syntheses and characterization of the imidazolate frameworks 3∞[Sm3(Im)9(ImH)2]·2ImH, Im– = imidazolate anion, ImH = 1H‐imidazole 3∞[Gd2(Im)6(ImH)1.5]·0.5ImH and 3∞[Dy(Im)3] it is shown that the constitution of 3D‐linked lanthanide imidazolates is variable and refers to the lanthanide contraction and the course of the ionic radii of Ln3+ and thus the coordinative demand of the referring ions. The larger the trivalent ion the more neutral imidazole molecules are incorporated, both coordinating and non‐coordinating starting with no imidazole and homoleptic frameworks for Ln = Tb, Dy and ranging to a ratio Ln:ImH of 1:2 for praseodymium in 3∞[Pr(Im)3(ImH)]·ImH. Samarium and gadolinium mark steps in this course with ratios of 3:4 and 1:1. Although the constitution differs, the lanthanide ions show only a slight change in C.N. ranging from six to seven. Major differences are observed in the framework structures and topologies as well as density concerning available free space after imidazole release. Kagomé nets are a prominent topological feature of imidazole containing constitutions, whereas cubic 4, 6 nets are found for homoleptic imidazolates.