3-Electron, Nonpolyhedral Cu Nanocluster Showing Distinct Dielectric, Magnetic, and Mechanical Properties

Cu nanoclusters represent a type of atomically precise nanomaterial that exhibits excellent catalytic performance. So far, exploration of the structural chemistry and study of the electronic (e.g., dielectric property), magnetic, and mechanical properties of Cu nanoclusters still remain in the early stage. In this work, we report a Cu nanocluster, [Cu₁₉(PPh₃)₄(PET)₁₆] (PPh₃ = triphenylphosphine; PET = 2-phenylethanethiol), which contains a special orthogonally packed triangular kernel with an unexpected three-valence-electron, open-shelled system. This result significantly differs from the polyhedral structures and the superatomic electronic configurations in previously reported Cu nanoclusters. The unpaired electrons in Cu₁₉ lead to paramagnetism, which is confirmed by a superconducting quantum interference device (SQUID). Of note, the solution-assembled Cu₁₉ crystal displays an unexpectedly high dielectric constant over a wide frequency range (∼75 at 1 kHz-1 MHz), which arises from the displacement of the valence electrons and the sharply increased dipole under the electric field. This performance exceeds that of most of the currently used solution-processable dielectric materials (e.g., polymers). Our work demonstrates the rich structural chemistry and the distinct electronic, magnetic, and mechanical properties of Cu nanoclusters and unveils their potential applications as high-performance, solution-processable dielectric materials.