Cationic Effects on the Net Hydrogen Atom Bond Dissociation Free Energy of High-Valent Manganese Imido Complexes
Issued Date
2022-02-02
Resource Type
ISSN
00027863
eISSN
15205126
Scopus ID
2-s2.0-85123569894
Pubmed ID
35041788
Journal Title
Journal of the American Chemical Society
Volume
144
Issue
4
Start Page
1503
End Page
1508
Rights Holder(s)
SCOPUS
Bibliographic Citation
Journal of the American Chemical Society Vol.144 No.4 (2022) , 1503-1508
Suggested Citation
Léonard N.G., Chantarojsiri T., Ziller J.W., Yang J.Y. Cationic Effects on the Net Hydrogen Atom Bond Dissociation Free Energy of High-Valent Manganese Imido Complexes. Journal of the American Chemical Society Vol.144 No.4 (2022) , 1503-1508. 1508. doi:10.1021/jacs.1c09583 Retrieved from: https://repository.li.mahidol.ac.th/handle/20.500.14594/84106
Title
Cationic Effects on the Net Hydrogen Atom Bond Dissociation Free Energy of High-Valent Manganese Imido Complexes
Author(s)
Author's Affiliation
Other Contributor(s)
Abstract
Local electric fields can alter energy landscapes to impart enhanced reactivity in enzymes and at surfaces. Similar fields can be generated in molecular systems using charged functionalities. Manganese(V) salen nitrido complexes (salen = N,N′-ethylenebis(salicylideneaminato)) appended with a crown ether unit containing Na+ (1-Na), K+, (1-K), Ba2+ (1-Ba), Sr2+ (1-Sr), La3+ (1-La), or Eu3+ (1-Eu) cation were investigated to determine the effect of charge on pKa, E1/2, and the net bond dissociation free energy (BDFE) of N-H bonds. The series, which includes the manganese(V) salen nitrido without an appended crown, spans 4 units of charge. Bounds for the pKa values of the transient imido complexes were used with the Mn(VI/V) reduction potentials to calculate the N-H BDFEs of the imidos in acetonitrile. Despite a span of >700 mV and >9 pKa units across the series, the hydrogen atom BDFE only spans 6 kcal/mol (between 73 and 79 kcal/mol). These results suggest that the incorporation of cationic functionalities is an effective strategy for accessing wide ranges of reduction potentials and pKa values while minimally affecting the BDFE, which is essential to modulating electron, proton, or hydrogen atom transfer pathways.