Assembly of high-valent oxomanganese clusters in aqueous solution. Redox equilibrium of water-stable Mn3O44+ and Mn2O23+ complexes

Characterization of synthetic oxomanganese complexes and the inorganic core of the O2-evolving complex in photosystem II: Evaluation of the DFT/B3LYP level of theory

“…However, the analysis of the energetics of various lowlying spin-states of complex 3 indicates that the DFT/ B3LYP level of theory erroneously predicts the ground electronic state to be the HS state (Mn 3 = +3/2, +3/2, À3/2), in disagreement with EPR measurements [5]. Furthermore, the DFT/B3LYP methodology erroneously predicts that the LS states (Mn 3 = +1/2, À3/2, +3/2) and (Mn 3 = +1/2, +1/2, À3/2) are, respectively, 21 kcal/mol and 41 kcal/mol above the ground electronic state.…”

“…The X-ray atomic coordinates of the Mn complexes were obtained from the Cambridge Crystallographic Data Center (CCDC) with reference codes FIQFIU [2], YEM-CIC [4], JEWNII [5], and HIRDIV [89]. All ab initio computations were performed at the DFT/B3LYP level of theory by using the programs Jaguar 5.5 [90] and Gaussian 03 [91].…”

“…Since the complex involves an odd number of Mn ions, there is unavoidable spin frustration because only two of the three Mn-Mn pairs can be anti-ferromagnetically coupled. In fact, it has been determined by EPR spectroscopy [5] that the (l-O) 2 Mn 2 unit has total spin S = 1 with either, or both, Mn 4+ ions in a low spin state S = 1/2. In addition, the total spin of the complex in the ground state is S = 1/2, indicat- Table 2 Comparison between DFT/B3LYP and experimental X-ray inter-atomic distances (Å ) in complex 2…”

“…High-valent multinuclear oxomanganese complexes have been extensively investigated both experimentally [1][2][3][4][5][6][7][8][9][10] and theoretically [11][12][13][14][15][16][17][18][19][20][21][22][23][24], due to their central role in catalytic water-splitting. In particular, structural rearrangements in multinuclear oxomanganese model complexes have been studied at the density functional theory (DFT) level, implemented in conjunction with hybrid density functionals (e.g., the Becke-3-Lee-Yang-Parr (B3LYP) functional) [11][12][13][14][15][16][17][18][19][20][21][22][23][24], a computational approach that has been identified as the most successful methodology in an overwhelming number of investigations in many areas of chemical research.…”

“…The calculations reported in this paper include four of these synthetic Mn-oxo complexes [2,4,5,89] 8+ cluster ion completely ligated with water, OH À and Cl À , a structure based on the inorganic core of the OEC modeled in the recent X-ray crystal structure of PSII obtained by Ferreira et al [27].…”