<P>A cobalt chlorin complex (Co<SUP>II</SUP>(Ch)) efficiently and selectively catalyzed two-electron reduction of dioxygen (O<SUB>2</SUB>) by one-electron reductants (ferrocene derivatives) to produce hydrogen peroxide (H...
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https://www.riss.kr/link?id=A107605166
2013
-
SCOPUS,SCIE
학술저널
2800-2808(9쪽)
0
상세조회0
다운로드다국어 초록 (Multilingual Abstract)
<P>A cobalt chlorin complex (Co<SUP>II</SUP>(Ch)) efficiently and selectively catalyzed two-electron reduction of dioxygen (O<SUB>2</SUB>) by one-electron reductants (ferrocene derivatives) to produce hydrogen peroxide (H...
<P>A cobalt chlorin complex (Co<SUP>II</SUP>(Ch)) efficiently and selectively catalyzed two-electron reduction of dioxygen (O<SUB>2</SUB>) by one-electron reductants (ferrocene derivatives) to produce hydrogen peroxide (H<SUB>2</SUB>O<SUB>2</SUB>) in the presence of perchloric acid (HClO<SUB>4</SUB>) in benzonitrile (PhCN) at 298 K. The catalytic reactivity of Co<SUP>II</SUP>(Ch) was much higher than that of a cobalt porphyrin complex (Co<SUP>II</SUP>(OEP), OEP<SUP>2–</SUP> = octaethylporphyrin dianion), which is a typical porphyrinoid complex. The two-electron reduction of O<SUB>2</SUB> by 1,1′-dibromoferrocene (Br<SUB>2</SUB>Fc) was catalyzed by Co<SUP>II</SUP>(Ch), whereas virtually no reduction of O<SUB>2</SUB> occurred with Co<SUP>II</SUP>(OEP). In addition, Co<SUP>II</SUP>(Ch) is more stable than Co<SUP>II</SUP>(OEP), where the catalytic turnover number (TON) of the two-electron reduction of O<SUB>2</SUB> catalyzed by Co<SUP>II</SUP>(Ch) exceeded 30000. The detailed kinetic studies have revealed that the rate-determining step in the catalytic cycle is the proton-coupled electron transfer reduction of O<SUB>2</SUB> with the protonated Co<SUP>II</SUP>(Ch) ([Co<SUP>II</SUP>(ChH)]<SUP>+</SUP>) that is produced by facile electron-transfer reduction of [Co<SUP>III</SUP>(ChH)]<SUP>2+</SUP> by ferrocene derivative in the presence of HClO<SUB>4</SUB>. The one-electron-reduction potential of [Co<SUP>III</SUP>(Ch)]<SUP>+</SUP> was positively shifted from 0.37 V (vs SCE) to 0.48 V by the addition of HClO<SUB>4</SUB> due to the protonation of [Co<SUP>III</SUP>(Ch)]<SUP>+</SUP>. Such a positive shift of [Co<SUP>III</SUP>(Ch)]<SUP>+</SUP> by protonation resulted in enhancement of the catalytic reactivity of [Co<SUP>III</SUP>(ChH)]<SUP>2+</SUP> for the two-electron reduction of O<SUB>2</SUB> with a lower overpotential as compared with that of [Co<SUP>III</SUP>(OEP)]<SUP>+</SUP>.</P><P><B>Graphic Abstract</B>
<IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/jacsat/2013/jacsat.2013.135.issue-7/ja312199h/production/images/medium/ja-2012-12199h_0018.gif'></P><P><A href='http://pubs.acs.org/doi/suppl/10.1021/ja312199h'>ACS Electronic Supporting Info</A></P>