An Antiferromagnetically Coupled Heterometal Cu₆Fe Wheel

Abstract

A heterometal Cu 6 Fe wheel molecule, [Cu II 6 Fe III (HL) 6 -(OH) 2 (OCH 3 ) 4 ](NO 3 ) 3 ¢6H 2 O (1¢6H 2 O) (H 2 L = 1-(2-pyridine)-3-(2-pyrrole)acetylacetone) was synthesized by the one-pot reaction of H 2 L with copper and iron sources. X-ray structural analysis reveals that the heptanuclear wheel cluster consists of a central Fe(III) ion surrounded by six Cu(II) ions, linked through methoxo-and hydroxo-bridges. Cryomagnetic studies indicate intramolecular antiferromagnetic interactions were operative. Heterometal polynuclear complexes exhibit physical properties and functions derived from the electronic and magnetic interactions between their constituent transition metal ions, and the search for new compounds with novel properties and functions continues to be an important area of research.1 In the field of biomolecular chemistry, several enzyme models with heterometallic active sites have been investigated.2 It is thus critical to find effective synthetic methods for heterometal clusters in order to better understand the reaction mechanisms of these active sites. Likewise, in materials chemistry, intermetal electronic/magnetic interactions between different metal ions also lead to specific physical properties.3 Heterometal systems can offer a convenient route to designable single-molecule magnets as the magnetic characters of different metal ions can lead to favorable orbital interactions and spin alignment. 4 It is well-known that heterometal mixed-valence systems, such as cyanide-bridged Co-Fe compounds, show external stimuli induced electron-transfer-coupled spin transitions.5 Heterometal complexes are attractive targets in many areas of chemistry and, as a result, new approaches to their controlled-syntheses are needed. Compartment-type ligands, which have distinct coordination sites for different metal ions, are very useful for assembling such species. 6 In recent times, many heterometal complexes have been constructed by exploiting the complexation stability constants of different metal ions. Self-assembly driven syntheses of heterometallic systems have also been serendipitously discovered.7 With these points in mind, advanced synthetic methods should be explored by using appropriate polydentate ligands and reaction conditions. We investigated a range of alkoxo-bridged polynuclear metal clusters, such as homometal [Mn 13 22 These heterometal rings are intensively investigated because of their potential application as spin qubits in quantum computing.In this work, we focus on the asymmetric multidentate bridging ligand, 1-(2-pyridine)-3-(2-pyrrole)acetylacetone (H 2 L), and its complexation reactions with copper and iron sources have been investigated. Herein, the structure and magnetic properties of the obtained heptanuclear Cu 6 Fe wheel complex are reported.To a methanol solution (15 mL) of Cu(NO 3 ) 2 ¢3H 2 O (24.2 mg, 0.1 mmol) was added a methanol solution (10 mL) of H 2 L (21.4 mg, 0.1 mmol) with trimethylamine (27.6¯L, 0.2 mmol). The resulting brown solution was stirred and a methanol ...

Design and Self-Assembly of Ferrocene-Functional Heterometal–Oxo Clusters with the M(III)4O4 Cubane Core

“…Through magnetic structure correlation analysis, we observed that the Cu–Fe distance in compound 1 is 3.369–3.457 Å and the Fe–Fe distance is 3.016–3.039 Å, indicating strong coupling between them. Meanwhile, the Cu–O–Fe angles in the structure are 118.0–121.2°, which dominate the antiferromagnetic interaction, which matched the χ M T curve between 170 and 300 K and Weiss constant θ . The Fe–O–Fe bond angles are in the range of 95.83–97.48°, and Fe–O falls in the range of 2.003–2.046 Å, dominating ferromagnetic interactions .…”

“…Meanwhile, the Cu−O−Fe angles in the structure are 118.0−121.2°, which dominate the antiferromagnetic interaction, which matched the χ M T curve between 170 and 300 K and Weiss constant θ. 43 The Fe−O− Fe bond angles are in the range of 95.83−97.48°, and Fe−O falls in the range of 2.003−2.046 Å, dominating ferromagnetic interactions. 44 The curve trend between 2 and 171 K of the M−T curve is consistent.…”