Electronic structure of the water-oxidation catalyst [(bpy)2(OHx)RuORu(OHy)(bpy)2]z+: weak coupling between the metal centers is preferred over strong coupling.
High-level DFT calculations indicate that the singlet ground state of the water-oxidizing blue Ru dimer [(bpy)2(OH2)RuIIIORuIII(OH2)(bpy)2]4+ is not due to a strong coupling of the excess electrons from each of the low-spin d5 RuIII centers across the Ru-O-Ru moiety, as has been assumed to date. Instead, broken symmetry orbital calculations suggest that a weak antiferromagnetically (AF) coupled singlet state is energetically more favorable by 10-35 kcal/mol. Experimentally observed redox potentials can only be reproduced if antiferromagnetic coupling is invoked.
Yang
Xiaofan
X
Department of Chemistry and School of Informatics, Indiana University, Bloomington, Indiana 47405, USA.
Baik
Mu-Hyun
MH