Discovery of a Ferromagnetic Nickel Chalcogenide Nanocluster Ni₃S₃H(PEt₃)₅

Atomically precise ligated nanoclusters (NC) are promising cluster-based materials with novel molecular architectures and tunable magnetic properties. Herein, the synthesis and characterization of a nickel sulfide NC Ni₃S₃H(PEt₃)₅ (PEt₃ = triethylphosphine) with distinct magnetic properties are reported. Magnetization measurements reveal its magnetic moment of 1.5 µ_B in the solid phase, consistent with the existence of one unpaired electron predicted by density functional theory (DFT) calculations. Additionally, experimental measurements indicate the presence of ferromagnetic ordering within each Ni₃S₃H(PEt₃)₅ NC and strong coercivity at temperatures below 20 K. Ion mobility-mass spectrometry is employed in conjunction with DFT calculations and collision cross-section simulations to investigate the structure of the isolated Ni₃S₃H(PEt₃)₅. Theoretical studies show that [Ni₃S₃H(PEt₃)₅]⁺ has a planar Ni₃S₃ core where three Ni atoms are arranged in a triangle with three bridging S atoms residing in the same plane. This structure is preserved in both solution and solid phases, which is confirmed by spectroscopic studies of Ni₃S₃H(PEt₃)₅. Additionally, DFT calculations indicate that all spins at the Ni sites are aligned parallel, confirming the presence of ferromagnetic coupling. Overall, this study provides key insights into the structure and magnetic properties of Ni₃S₃H(PEt₃)₅, which will facilitate the design of new NC-based magnetic materials.