Eight-Electron Superatomic Cu₃₁ Nanocluster with Chiral Kernel and NIR-II Emission

Area of Science:

• Inorganic Chemistry
• Materials Science
• Nanotechnology

Background:

• Copper nanoclusters are less common than silver or gold due to inherent instability.
• Low Cu(I)/Cu(0) half-cell reduction potential challenges the formation of Cu(0)-containing nanoclusters.

Purpose of the Study:

• To synthesize and structurally characterize a novel eight-electron superatomic copper nanocluster.
• To investigate the unique electronic and optical properties of the synthesized copper nanocluster.
• To explore the potential of this copper nanocluster in biological applications.

Main Methods:

• Total structural characterization of the copper nanocluster.
• Electrospray ionization mass spectrometry (ESI-MS).
• X-ray photoelectron spectroscopy (XPS).
• Density functional theory (DFT) calculations.

Main Results:

• A novel eight-electron superatomic copper nanocluster, [Cu31(4-MeO-PhC≡C)21(dppe)3](ClO4)2, was synthesized and characterized.
• The nanocluster possesses a chiral metal core with a unique helical arrangement of Cu2 units around a Cu13 core.
• It exhibits the first observed near-infrared (NIR-I) absorption and second near-infrared (NIR-II) emission in copper nanoclusters.
• The 4-methoxy groups on the ligands are crucial for cluster formation and crystallization.

Conclusions:

• This work presents a new member of the copper superatom family with unprecedented electronic properties.
• The synthesized copper nanocluster demonstrates significant potential for biological applications due to its NIR optical properties.
• Copper nanoclusters, previously considered nonluminous in the visible range, can exhibit deep NIR luminescence.