Observation of Non-FCC Copper in Alkynyl-Protected Cu53 Nanoclusters

The only feasible access to non-face-centered cubic (FCC) copper was by physical vapor deposition under high vacuum. Now, non-FCC copper is observed in a series of alkynyl-protected Cu-53 nanoclusters (NCs) obtained from solution-phase synthesis. Determined by single-crystal X-ray crystallography, the structures of Cu-53(C equivalent to CPhPh)(9)(dppp)(6)Cl-3(NO3)(9) and its two derivatives reveal an ABABC stacking sequence involving 41 Cu atoms. It can be regarded as a mixed FCC and HCP structure, which gives strong evidence that Cu can be arranged in non-FCC lattice at ambient conditions when proper ligands are provided. Characterization methods including X-ray absorption fine structure, XPS, ESI-MS, UV/Vis, Auger spectroscopy, and DFT calculations were carried out. Cu-II was shown to successively coordinate with introduced ligands and changed to Cu-I after bonding with phosphine. The following addition of NaBH4 and the aging step further reduced it to the Cu-53 NC.