TY - JOUR
T1 - Deuterium kinetic isotope effects as redox mechanistic criterions
AU - Fukuzumi, Shunichi
AU - Lee, Yong Min
AU - Nam, Wonwoo
N1 - Funding Information:
The authors thankfully acknowledge the contributions of their collaborators and co‐workers cited in the references, and financial supports from JSPS (Grant Numbers 16H02268 to Shunichi Fukuzum) from Ministry of Education, Culture, Sports, Science and Technology (MEXT), Japan and from the National Research Foundation (NRF) of Korea through the CRI (NRF‐2021R1A3B1076539 to Wonwoo Nam) and Basic Science Research Program (NRF‐2020R1I1A1A01074630 to Yong‐Min Lee and NRF‐2017R1D1A1B03032615 to Shunichi Fukuzumi).
Funding Information:
NRF of Korea, Grant/Award Numbers: 2017R1D1A1B03032615, 2020R1I1A1A01074630, 2021R1A3B1076539; Ministry of Education, Culture, Sports, Science and Technology; JSPS, Grant/Award Number: 16H02268 Funding information
Publisher Copyright:
© 2021 Korean Chemical Society, Seoul & Wiley-VCH GmbH
PY - 2021/12
Y1 - 2021/12
N2 - This account article focuses on deuterium kinetic isotope effects (KIEs) used as criterions to elucidate redox mechanisms including proton-, hydrogen- and hydride-transfer reactions. Hydrogen atom transfer (HAT) is composed of two elementary steps: electron transfer (ET) and proton transfer (PT), while hydride transfer is composed of three elementary steps: ET, PT, and ET. Large tunneling effects are often observed for proton-coupled electron-transfer (PCET) reactions of metal–oxygen complexes in which ET occurs to the metal center and PT occurs simultaneously to the ligand, exhibiting large KIEs. Whether HAT proceeds via sequential ET/PT, PT/ET, or concerted PCET (cPCET) depending on the redox properties of hydrogen donors and acceptors to exhibit different KIEs. Whether hydride transfer also proceeds via sequential ET/PT/ET, PT/ET/ET, or cPCET/ET depending on the redox properties of hydride donors and acceptors to exhibit different KIEs. Temperature dependence of KIEs for aldehyde deformylation reactions has enabled to distinguish two reaction pathways: one is a HAT and the other is a nucleophilic addition. The change of the mechanism from cPCET to sequential ET/PT is made possible by binding acids to the hydrogen and hydride acceptors when no KIE is observed. Inverse KIEs are also discussed for acid (or deuteron)-promoted ET reactions.
AB - This account article focuses on deuterium kinetic isotope effects (KIEs) used as criterions to elucidate redox mechanisms including proton-, hydrogen- and hydride-transfer reactions. Hydrogen atom transfer (HAT) is composed of two elementary steps: electron transfer (ET) and proton transfer (PT), while hydride transfer is composed of three elementary steps: ET, PT, and ET. Large tunneling effects are often observed for proton-coupled electron-transfer (PCET) reactions of metal–oxygen complexes in which ET occurs to the metal center and PT occurs simultaneously to the ligand, exhibiting large KIEs. Whether HAT proceeds via sequential ET/PT, PT/ET, or concerted PCET (cPCET) depending on the redox properties of hydrogen donors and acceptors to exhibit different KIEs. Whether hydride transfer also proceeds via sequential ET/PT/ET, PT/ET/ET, or cPCET/ET depending on the redox properties of hydride donors and acceptors to exhibit different KIEs. Temperature dependence of KIEs for aldehyde deformylation reactions has enabled to distinguish two reaction pathways: one is a HAT and the other is a nucleophilic addition. The change of the mechanism from cPCET to sequential ET/PT is made possible by binding acids to the hydrogen and hydride acceptors when no KIE is observed. Inverse KIEs are also discussed for acid (or deuteron)-promoted ET reactions.
KW - acid-promoted electron transfer
KW - deuterium kinetic isotope effect
KW - inverse kinetic isotope effect
KW - proton-coupled electron transfer
KW - tunneling effect
UR - http://www.scopus.com/inward/record.url?scp=85118877724&partnerID=8YFLogxK
U2 - 10.1002/bkcs.12417
DO - 10.1002/bkcs.12417
M3 - Review article
AN - SCOPUS:85118877724
SN - 0253-2964
VL - 42
SP - 1558
EP - 1568
JO - Bulletin of the Korean Chemical Society
JF - Bulletin of the Korean Chemical Society
IS - 12
ER -