Structural Characterization of a Series of N5-Ligated MnIV-Oxo Species |
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Authors: | Dr Allyssa A Massie Dr Melissa C Denler Dr Reena Singh Dr Arup Sinha Prof Dr Ebbe Nordlander Prof Dr Timothy A Jackson |
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Institution: | 1. Department of Chemistry and Center for Environmentally, Beneficial Catalysis, The University of Kansas, 1567 Irving Hill Road, Lawrence, KS, 66045 USA;2. Chemical Physics, Department of Chemistry, Lund University, Box 124, 221 00 Lund, Sweden;3. Chemical Physics, Department of Chemistry, Lund University, Box 124, 221 00 Lund, Sweden
Department of Chemistry, School of Advanced Science, Vellore Institute of Technology, Vellore, 632014 Tamil Nadu, India |
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Abstract: | Analysis of extended X-ray absorption fine structure (EXAFS) data for the MnIV-oxo complexes MnIV(O)(DMMN4py)]2+, MnIV(O)(2pyN2B)]2+, and MnIV(O)(2pyN2Q)]2+ (DMMN4py=N,N-bis(4-methoxy-3,5-dimethyl-2-pyridylmethyl)-N-bis(2-pyridyl)methylamine; 2pyN2B=(N-bis(1-methyl-2-benzimidazolyl)methyl-N-(bis-2-pyridylmethyl)amine, and 2pyN2Q=N,N-bis(2-pyridyl)-N,N-bis(2-quinolylmethyl)methanamine) afforded Mn=O and Mn−N bond lengths. The Mn=O distances for MnIV(O)(DMMN4py)]2+ and MnIV(O)(2pyN2B)]2+ are 1.72 and 1.70 Å, respectively. In contrast, the Mn=O distance for MnIV(O)(2pyN2Q)]2+ was significantly longer (1.76 Å). We attribute this long distance to sample heterogeneity, which is reasonable given the reduced stability of MnIV(O)(2pyN2Q)]2+. The Mn=O distances for MnIV(O)(DMMN4py)]2+ and MnIV(O)(2pyN2B)]2+ could only be well-reproduced using DFT-derived models that included strong hydrogen-bonds between second-sphere solvent 2,2,2-trifluoroethanol molecules and the oxo ligand. These results suggest an important role for the 2,2,2-trifluoroethanol solvent in stabilizing MnIV-oxo adducts. The DFT methods were extended to investigate the structure of the putative MnIV(O)(N4py)]2+⋅(HOTf)2 adduct. These computations suggest that a MnIV-hydroxo species is most consistent with the available experimental data. |
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Keywords: | DFT calculations electronic structure oxido ligands spectroscopy X-ray absorption spectroscopy |
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