Fig. 4

Quantum mechanical studies of alkyne coordination to gold subnanoclusters. a Calculated thermodynamic cycle for alkyne coordination and Au₃ dimerization. The different coordination abilities of phenylacetylene (4) and linear alkynes 1-hexyne (1), 1-docecyne (2) and benzylacetylene (3) to Au₃ and Au₆ subnanoclusters are estimated based on the calculated free energies for each equilibrium (ΔG _coord, in blue). The preference of each nanocluster (Au₃ or Au₆) to bind the different alkynes is calculated through the corresponding exchange free energies (ΔG _exch, in green). The ability of each alkyne to stabilize small (Au₃) or bigger (Au₆) subnanoclusters is derived from the calculated dimerization free energies (ΔG _dim, in red). b Minimum energy structures and van der Waals surfaces calculated for Au₃-(1–4) complexes. Interatomic distances between the gold atoms and alkyne (in red) and side chain atoms (in gray) are shown as dashed lines and given in angstrom. Only Au···C–H and Au···π contacts below 4 Å are shown. See Supplementary Fig. 9, Supplementary Table 3, and Supplementary Methods for further details