A Fan-Shaped Polynuclear Gd₆Cu₁₂ Amino Acid Cluster: A “Hollow” and Ferromagnetic [Gd₆(μ₃-OH)₈] Octahedral Core Encapsulated by Six [Cu₂] Glycinato Blade Fragments

Abstract

By a stepwise growth process, an axial-fan-like and high-nuclearity [Gd6Cu12] cluster compound (1) was obtained, in which six [Cu2] blade fragments encapsulate a "hollow" [Gd6(μ3-OH)8] octahedral core. Without the support of a centered μ6-O ligand for the octahedral core, its mean Gd−μ3-O−Gd bridging angle (φ) is the largest one among the polynuclear [Gdn] (n ≥ 3) clusters. From the exchange and structural parameters of the reported complexes containing the GdO2Gd unit, an empirical formula was at the first time obtained. It can be concluded that φ > 110.9° is a prerequisite for a GdO2Gd complex exhibiting molecular ferromagnetism. The positive exchange constants for the Gd−Gd coupling from the empirical estimation and data fitting suggest the [Gd6] core in 1 is the first example of high-nuclearity Lnn cluster exhibiting the molecular ferromagnetism. The magnetic property for 1 is mainly predominated by the antiferromagnetic interaction of Cu−Cu coupling and the ferromagnetic interactions of Gd−Gd and of Gd−Cu coupling. At low field, 1 is a frustrated ferrimagnet, while it exhibits a single-ion behavior of Gd3+ ions at high field.