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.