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Oxo- and hydroxomanganese(IV) adducts: a comparative spectroscopic and computational study
Swarup Chattopadhyay1, Robert A Geiger, Guochuan Yin
1Department of Chemistry and Center for Environmentally Beneficial Catalysis, University of Kansas, 1251 Wescoe Hall Drive, Lawrence, Kansas 66045, USA.
Inorganic Chemistry
|August 10, 2010
Summary
This study investigated manganese complexes using spectroscopy, revealing electronic structure differences. These findings explain modest rate enhancements in hydrogen atom transfer reactions involving manganese-oxo and manganese-hydroxo species.
Area of Science:
- Inorganic Chemistry
- Computational Chemistry
- Spectroscopy
Background:
- Manganese complexes are crucial in various catalytic processes.
- Understanding the electronic structure of manganese-oxo and manganese-hydroxo species is key to elucidating reaction mechanisms.
Purpose of the Study:
- To probe and compare the electronic structures of bis(hydroxo)manganese(IV) and oxohydroxomanganese(IV) complexes.
- To correlate electronic structure with reactivity in hydrogen atom transfer reactions.
Main Methods:
- Electronic absorption spectroscopy
- Magnetic circular dichroism (MCD) spectroscopy (variable-temperature, variable-field)
- Time-dependent density functional theory (TD-DFT) computations
- Group theory analysis
Main Results:
- Assigned d-d transitions for the bis(hydroxo)manganese(IV) complex, providing insights into pi and sigma interactions.
- Observed increased ligand character in Mn pi* orbitals for the Mn(IV)=O complex compared to the Mn(IV)OH complex.
- Found minimal changes in Mn sigma* orbital compositions between the two complexes.
Conclusions:
- The electronic structure differences, particularly in pi* orbitals, were characterized.
- Steric factors and sigma* orbital compositions suggest a common pathway for H-atom transfer in both complexes.
- Modest rate enhancements for Mn(IV)=O over Mn(IV)OH species in H-atom transfer are attributed to these electronic and steric features.
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