Ni(12) tetracubane cores with slow relaxation of magnetization and efficient charge utilization for photocatalytic hydrogen evolution

We report two Ni(12) multicubane topologies enclosed in the polyanions [Ni(12)(OH)(9)(WO(4))(3)(PO(4))(B-α-PW(9)O(34))(3)](21−){Ni(12)W(30)} and [Ni(12)(OH)(9)(HPO(4))(3)(PO(4))(B-α-PW(9)O(34))(A-α-PW(9)O(34))(2)](21−){Ni(12)W(27)} that magnetically behave as Ni(12) units clearly distinguishing them from typical Ni(4) cubanes as shown by magnetic studies together with high field and frequency electron paramagnetic resonance (HFEPR). Beyond the unprecedented static properties, {Ni(12)W(30)} shows the unusual coexistence of slow relaxation of the magnetization and a diamagnetic ground state (S = 0), providing the unique opportunity of studying the essentially elusive magnetic relaxation behavior in excited states. The cubane-topology dependent activity of {Ni(12)W(30)} and {Ni(12)W(27)} as homogeneous HER photocatalysts unveils the structural key features significant for the design of photocatalysts with efficient charge utilization exemplified by high quantum yields (QY) of 10.42% and 8.36% for {Ni(12)W(30)} and {Ni(12)W(27)}, respectively.