Solid-State <sup>55</sup>Mn NMR Spectroscopy of Bis(μ-oxo)dimanganese(IV) [Mn<sub>2</sub>O<sub>2</sub>(salpn)<sub>2</sub>], a Model for the Oxygen Evolving Complex in Photosystem II

We have examined the antiferromagneticly coupled bis(μ-oxo)dimanganese(IV) complex [Mn<sub>2</sub>O<sub>2</sub>(salpn)<sub>2</sub>] (<b>1</b>) with <sup>55</sup>Mn solid-state NMR at cryogenic temperatures and first-principle theory. The extracted values of the <sup>55</sup>Mn quadrupole coupling constant, <i>C</i><sub>Q</sub>, and its asymmetry parameter, η<sub>Q</sub>, for <b>1</b> are 24.7 MHz and 0.43, respectively. Further, there was a large anisotropic contribution to the shielding of each Mn<sup>4+</sup>, i.e. a Δσ of 3375 ppm. Utilizing broken symmetry density functional theory, the predicted values of the electric field gradient (EFG) or equivalently the <i>C</i><sub>Q</sub> and η<sub>Q</sub> at ZORA, PBE QZ4P all electron level of theory are 23.4 MHz and 0.68, respectively, in good agreement with experimental observations.