Two Decanuclear DyIIIxCoII10-x (x = 2, 4) Nanoclusters: Structure, Assembly Mechanism, and Magnetic Properties

The aggregation and formation of heterometallic nanoclusters usually involves a variety of complex self-assembly processes; thus, the exploration of their assembly mechanisms through process tracking is more challenging than that for homometallic nanoclusters. We explored here the effect of solvent on the formation of heterometallic clusters, which gave two heterometallic nanoclusters, [Dy₂Co₈(μ₃-OCH₃)₂(L)₄(HL)₂(OAc)₂(NO₃)₂(CH₃CN)₂]·CH₃CN·H₂O (1) and [Dy₄Co₆(L)₄(HL)₂(OAc)₆(OCH₂CH₂OH)₂(HOCH₂CH₂OH)(H₂O)]·9CH₃CN (2), with the H₃L ligand formed from the in situ condensation reaction of 3-amino-1,2-propanediol with 2-hydroxy-1-naphthaldehyde in the presence of Co(OAc)₂·4H₂O and Dy(NO)₃·6H₂O. It is worth noting that the skeleton of cluster 1 has a high stability under high-resolution electrospray ionization mass spectrometry (HRESI-MS) conditions with a gradually increasing energy of the ion source. Cluster 2 underwent a multistep fragmentation even under a zero ion-source voltage for the measurement of HRESI-MS. Further analysis showed that cluster 2 underwent a possible fragmentation mechanism of Dy₄Co₆L₆ → Dy₂Co₆L₅/DyL → DyCo₂L₃/DyCo₂L → DyL/Co₂L₂. Most notably, the species emerging in the formation process of cluster 1 were tracked using time-dependent HRESI-MS, from which we proposed its possible formation mechanism of H₂L → Co₂L₂ → Co₂DyL₂/Co₃L₂ → Co₃DyL₂ → Co₄DyL₂ → Co₅Dy₂L₄ → Co₈Dy₂L₆. As far as we know, it is the first time to track the formation process of Dy-Co heterometallic clusters through HRESI-MS with the proposed assembly mechanism. The magnetic properties of the two titled Dy^III_xCo^II_10-x (x = 2, 4) clusters were studied. Both of them exhibit slow magnetic relaxation, and 1 is a single-molecule magnet at zero direct-current field.

Quantum Monte Carlo simulations of a giant {Ni21Gd20} cage with a S = 91 spin ground state

The detailed analysis of magnetic interactions in a giant molecule is difficult both because the synthesis of such compounds is challenging and the number of energy levels increases exponentially with the magnitude and number of spins. Here, we isolated a {Ni₂₁Gd₂₀} nanocage with a large number of energy levels (≈5 × 10³⁰) and used quantum Monte Carlo (QMC) simulations to perform a detailed analysis of magnetic interactions. Based on magnetization measurements above 2 K, the QMC simulations predicted very weak ferromagnetic interactions that would give a record S = 91 spin ground state. Low-temperature measurements confirm the spin ground state but suggest a more complex picture due to the single ion anisotropy; this has also been modeled using the QMC approach. The high spin and large number of low-lying states lead to a large low-field magnetic entropy (14.1 J kg^-1 K^-1 for ΔH = 1 T at 1.1 K) for this material.

Ionothermal synthesis, crystal structure, topology and catalytic properties of heterometallic coordination polymers constructed from N-(phosphonomethyl) iminodiacetic acid

Four FeLn heterometallic coordination polymers with the H₄pmida ligand were ionothermally synthesized and characterized. Their catalytic properties in the Knöevenagel condensation reaction were investigated.