Observation of Non-FCC Copper in Alkynyl-Protected Cu 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 nanoclusters (NCs) obtained from solution-phase synthesis. Determined by single-crystal X-ray crystallography, the structures of Cu (C≡CPhPh) (dppp) Cl (NO ) 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 was shown to successively coordinate with introduced ligands and changed to Cu after bonding with phosphine. The following addition of NaBH and the aging step further reduced it to the Cu NC.