Heuristic rules that allow identifying the preferred mixed‐valence isomers and Jahn‐Teller axis arrangements in the water oxidation catalyst [(Mn4O4)(V4O13)(OAc)3]n− and its activated form [(Mn4O4)(V4O13)(OAc)2(H2O)(OH)]n− are derived. These rules are based on computing all combinatorially possible mixed‐valence isomers and Jahn‐Teller axis arrangements of the MnIII atoms, and associate energetic costs with some structural features, like crossings of multiple Jahn‐Teller axes, the location of these axes, or the involved ligands. It is found that the different oxidation states localize on different Mn centers, giving rise to clear Jahn‐Teller distortions, unlike in previous crystallographic findings where an apparent valence delocalization was found. The low barriers that connect different Jahn‐Teller axis arrangements suggest that the system quickly interconverts between them, leading to the observation of averaged bond lengths in the crystal structure. We conclude that the combination of cubane‐vanadate bonds that are chemically inert, cubane‐acetate/water bonds that can be activated through a Jahn‐Teller axis, and low activation barriers for intramolecular rearrangement of the Jahn‐Teller axes plays an essential role in the reactivity of this and probably related compounds.

We report IR and UV/Vis spectroscopic signatures that allow discriminating between the oxidation states of the manganese-based water oxidation catalyst [(Mn 4 O 4 )(V 4 O 13 )(OAc) 3 ] 3À . Simulated IR spectra show that V=O stretching vibrations in the 900-1000 cm À 1 region shift consistently by about 20 cm À 1 per oxidation equivalent. Multiple bands in the 1450-1550 cm À 1 region also change systematically upon oxidation/reduction. The computed UV/Vis spectra predict that the spectral range above 350 nm is characteristic of the managanese-oxo cubane oxidation state, whereas transitions at higher energy are due to the vanadate ligand. The presence of absorption signals above 680 nm is indicative of the presence of Mn III atoms. Spectroelectrochemical measurements of the oxidation from [Mn III 2 Mn IV 2 ] to [Mn IV 4 ] showed that the change in oxidation state can indeed be tracked by both IR and UV/Vis spectroscopy.

We report Jahn–Teller effects in different oxidation states of the water oxidation catalyst [(Mn4O4)(V4O13)(OAc)3]n- and its activated form [(Mn4O4)(V4O13)(OAc)2(H2O)(OH)]n-. Based on all combinatorially possible Jahn–Teller axis arrangements of the Mn(III) atoms, the energetically stable minima are identified. We also derive five heuristic rules that associate a particular energetic cost with certain structural features, like crossings of multiple Jahn–Teller axes, the location of Jahn–Teller axes, or the ligand that is involved in a Jahn–Teller axis. It is found that the different oxidation states seem to localize on different Mn centers, giving rise to clear Jahn–Teller distortions, unlike in previous crystallographic findings where an apparent valence delocalization was found. We conclude that the combination of cubane-vanadate bonds that are chemically inert, cubane-acetate/water bonds that can be activated through a Jahn–Teller axis, and low activation barriers for intramolecular rearrangement of the Jahn–Teller axes plays an important role in the reactivity of this and related compounds.

We report Jahn-Teller e ects in di erent oxidation states of the water oxidation catalyst [(Mn 4 O 4 )(V 4 O 13 )(OAc) 3 ] − and its activated form [(Mn 4 O 4 )(V 4 O 13 )(OAc) 2 (H 2 O)(OH)] − . Based on all combinatorially possible Jahn-Teller axisarrangements of the Mn III atoms, the energetically stable minima are identi ed. We also derive ve heuristic rules that associate a particular energetic cost with certain structural features, like crossings of multiple Jahn-Teller axes, the location of Jahn-Teller axes, or the ligand that is involved in a Jahn-Teller axis. It is found that the di erent oxidation states seem to localize on di erent Mn centers, giving rise to clear Jahn-Teller distortions, unlike in previous crystallographic ndings where an apparent valence delocalization was found. We conclude that the combination of cubane-vanadate bonds that are chemically inert, cubane-acetate/water bonds that can be activated through a Jahn-Teller axis, and low activation barriers for intramolecular rearrangement of the Jahn-Teller axes plays an important role in the reactivity of this and related compounds. V 4 O 6− 13 Mn 4 O m+ 4 AcO − AcO − AcO − (a) precatalyst V 4 O 6− 13