Computational Insights of Selective Intramolecular O-atom Transfer Mediated by Bioinspired Copper Complexes.

The stereoselective copper-mediated hydroxylation of intramolecular C-H bonds from tridentate ligands is reinvestigated using DFT calculations. The computational study aims at deciphering the mechanism of C-H hydroxylation obtained after reaction of Cu(I) precursors with dioxygen, using ligands bearing either activated (L1 ) or non-activated (L2 ) C-H bonds. Configurational analysis allows rationalization of the experimentally observed regio- and stereoselectivity. The computed mechanism involves the formation of a side-on peroxide species (P) in equilibrium with the key intermediate bis-(µ-oxo) isomer (O) responsible for the C-H activation step. The P/O equilibrium yields the same activation barrier for the two complexes. However, the main difference between the two model complexes is observed during the C-H activation step, where the complex bearing the non-activated C-H bonds yields a higher energy barrier, accounting for the experimental lack of reactivity of this complex under those conditions.

Self-assembled nickel cubanes as oxygen evolution catalysts.

Ni4O4 cubanes [(µ3-L1O)NiCl(MeOH)]4 (1) and [(µ3-L2O)NiCl(H2O)]4 (2) (L1OH = 1-H-2-benzimidazolylmethanol, L2OH = 1-methyl-2-benzimidazolylmethanol) self-assemble from commercially available 1-H- and 1-methyl-2-benzimidazolylmethanol and NiCl2·6H2O in high yields under mild conditions. Both complexes were characterised spectroscopically and by X-ray crystallography. The cubanes oxidise water electrocatalytically to dioxygen at neutral pH in aqueous potassium phosphate buffer solutions.