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.