Resolving an Anomalous Ultrashort Cu-Cu Bond in the Ag₁₆Cu₁₈(C≡C-C₆H₁₁)₂₄ Nanocluster: A Structural Reinterpretation...

Area of Science:

• Inorganic Chemistry
• Materials Science
• Computational Chemistry

Background:

• A bimetallic nanocluster Ag16Cu18(C≡C-C6H11)24 was reported with an unusually short Cu-Cu bond (1.62 Å).
• This reported bond length is significantly shorter than typical metallic bonds and approaches C-C single bond lengths.

Purpose of the Study:

• To investigate the origin of the anomalously short Cu-Cu bond in the Ag16Cu18 nanocluster.
• To re-evaluate the crystallographic structure and reconcile experimental data with theoretical principles.

Main Methods:

• Comprehensive density functional theory (DFT) investigations.
• Detailed crystallographic structural analysis and re-refinement.
• Comparison of experimental data with electronic-structure principles.

Main Results:

• The exceptionally short Cu-Cu bond was identified as a crystallographic misinterpretation.
• Re-refinement revealed the central Cu6 ring is a superposition of two Ag3 triangular units (50% occupancy each).
• The molecular formula was revised to Ag19Cu12(C≡C-C6H11)24, with improved R-factors (5.81% to 5.23%).

Conclusions:

• The anomalously short Cu-Cu bond is an artifact of crystallographic interpretation.
• The revised structure of Ag19Cu12 provides a chemically consistent explanation for experimental observations.
• This study highlights the importance of rigorous structural analysis in understanding bimetallic nanoclusters.