Synthesis and structural characterization of inverse-coordination clusters from a two-electron superatomic copper nanocluster

We have synthesized and structurally characterized a series of centred cuboctahedral copper clusters, namely [Cu-13{S2CNR2}(6){C?CR}(4)](PF6), 1a-d (where a: R = Bu-n, R = CO2Me; b: R = Bu-n, R = CO2Et; c: R = Pr-i, R = CO2Et; d: R = Pr-n, R = 3,5-(CF3)(2)C6H3); [Cu-12((12)-S){S2CNR2}(6){C?CR}(4)], 2a-c; [Cu-12((12)-Cl){S2CNR2}(6){C?CR}(4)](PF6), 3a-e (where e: R = Bu-n, R = Ph); [Cu-12((12)-Br){(S2CNBu2)-Bu-n}(6){C?CPh}(4)](PF6), 4e; and [Cu-12((12)-Cl)((3)-Cl){(S2CNBu2)-Bu-n}(6){C?CCO2Me}(3)](+)5a. Cluster 1a is the first structurally characterized copper cluster having a Cu-13 centered cuboctahedral arrangement, a miniature of the bulk copper fcc structure. Furthermore, the partial Cu(0) character in the 2-electron superatoms 1 was confirmed by XANES. Inverse coordination clusters 2-5 are the first examples of copper clusters containing main group elements (Cl, Br, S) with a hyper-coordination number, twelve. A combined theoretical and experimental study was performed, which shows that the central copper (formally Cu1-) in nanoclusters 1 can be replaced by chalcogen/halogen atoms, resulting in the formation of clusters 2-5 which show enhanced luminescence properties and increase in the ionic component of the host-guest interaction as Br approximate to Cl > S > Cu, which is consistent with the Cu-X Wiberg indices. The new compounds have been characterized by ESI-MS, H-1, C-13 NMR, IR, UV-visible, emission spectroscopy, and the structures 2a-b, 3d-e, 4e and 5a were established by X-ray diffraction analysis.