2016 1007_nano bio
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Department of Biochemistry& Molecular ChemistryDoshisha UniversityThe Hitomi Group
Preparation and Characterization of a Series of Iron(III) Hydroperoxo Species
Having a Carboxamido Ligand
1st Nano/Bio Science International Symposium October 7, 2016
Ryosuke Sakai
Department of Applied Chemistry, Graduate School of Science and Engineering, Doshisha University
1
Department of Biochemistry& Molecular ChemistryDoshisha UniversityThe Hitomi Group
Fe-bleomycin ( Fe-BLM )
* Ligand
Lei V Liu. et al., Proc. Natl. Acad. Aci.U. S. A. 2010, 107, 22419.
O
NH
HO
OCH3
HN
HO
O
(Me)2+S
HN
NH
NH*
O*N
H2N
N
NH*
NH2O
NH
*NO
O
O
OH
HOO
O
OH
OHOH
O
NH2O
OH
S
N
SNO
NH2
*NH2
H
H
H
H
H
metal binding domain
carbohydrate domain
DNA binding domain
Bleomycin (BLM), a glycopeptide antibiotic chemotherapy agent, is capable of single- and double- strand DNA damage.
https://mink.nipponkayaku.co.jp/index2.html.
2
Department of Biochemistry& Molecular ChemistryDoshisha UniversityThe Hitomi Group
Proposed reaction schemes of DNA oxidation
FeV(BLM) + H2O
O
FeIV(BLM) + H2O + R
O
FeIV(BLM) + OH
O
FeIII(BLM)
OOH
FeII(BLM)
O2
FeIII(BLM)O2
e-, H+
activated bleomycin(ABLM)
heterolytic cleavage
homolytic cleavage
direct H-atom abstraction
R-H
H+
Decker, A; Chow, M. S.; Kemsley, J. N.; Lehnert, N.; Solomon, E. I. J. Am. Chem. Soc. 2006, 128, 4719–4733.
The low-spin Fe–OOH complex (ABLM) is the last detectable species prior to DNA cleavage.
NH2
H2NOC
NH
FeN
NO
N
N
N
O
O
H2NOC
H2N
Activated bleomycin
H
CH3
OOH
Which?
EPR, Mössbauer ENDOR, MS, XAS, MCD
3
Department of Biochemistry& Molecular ChemistryDoshisha UniversityThe Hitomi Group
Proposed reaction schemes of DNA oxidation
FeV(BLM) + H2O
O
FeIV(BLM) + H2O + R
O
FeIV(BLM) + OH
O
FeIII(BLM)
OOH
FeII(BLM)
O2
FeIII(BLM)O2
e-, H+
activated bleomycin(ABLM)
heterolytic cleavage
homolytic cleavage
direct H-atom abstraction
R-H
H+
E. Solomon and coworkers suggested that ABLM is thermodynamically and kinetically competent for H-atom abstraction.
Decker, A; Chow, M. S.; Kemsley, J. N.; Lehnert, N.; Solomon, E. I. J. Am. Chem. Soc. 2006, 128, 4719–4733.
NH2
H2NOC
NH
FeN
NO
N
N
N
O
O
H2NOC
H2N
Activated bleomycin
H
CH3
OOH
4
Department of Biochemistry& Molecular ChemistryDoshisha UniversityThe Hitomi Group
Proposed reaction schemes of DNA oxidation
FeV(BLM) + H2O
O
FeIV(BLM) + H2O + R
O
FeIV(BLM) + OH
O
FeIII(BLM)
OOH
FeII(BLM)
O2
FeIII(BLM)O2
e-, H+
activated bleomycin(ABLM)
heterolytic cleavage
homolytic cleavage
direct H-atom abstraction
R-H
H+
E. Solomon and coworkers suggested that ABLM is thermodynamically and kinetically competent for H-atom abstraction.
Decker, A; Chow, M. S.; Kemsley, J. N.; Lehnert, N.; Solomon, E. I. J. Am. Chem. Soc. 2006, 128, 4719–4733.
NH2
H2NOC
NH
FeN
NO
N
N
N
O
O
H2NOC
H2N
Activated bleomycin
H
CH3
OOH
5
Department of Biochemistry& Molecular ChemistryDoshisha UniversityThe Hitomi Group
NH2
H2NOC
NH
FeN
NO
N
N
N
O
O
H2NOC
H2N
Activated bleomycin
H
CH3
OOH
Carboxamido Coordination
FeIII –bleomycin has a calboxamido ligand to the ferric center.
amido
6
Department of Biochemistry& Molecular ChemistryDoshisha UniversityThe Hitomi Group
NH2
H2NOC
NH
FeN
NO
N
N
N
O
O
H2NOC
H2N
Activated bleomycin
H
CH3
OOH
Iron Complex Having a Carboxamido Ligand
carboxylamido
R = OMe, H, Cl, NO2
FeIIIdpaqR
FeN NN
O
NN
N
(ClO4)2
CCH3 2+
Iron(III) complex with a nitrogen–based pentadentate ligand
having one carboxamide functionality, FeIIIdpaqR.
Hitomi, Y.; Arakawa, K.; Kodera, M. Chem. Eur. J. 2013, 19, 14697–14701. Hitomi, Y.; Iwamoto, Y.; Kodera, M. Dalton Trans. 2014, 43, 2161–2167.
7
Department of Biochemistry& Molecular ChemistryDoshisha UniversityThe Hitomi Group
Substituent Effect
FeN NN
O
NN
O+
OMe
OH
Substituent effect on the electreonic structres of the Fe–OOH speceis?
Electron withdrawing
FeN NN
O
NN
O+
H
OH
FeN NN
O
NN
O+
Cl
OH
FeN NN
O
NN
O+
NO2
OH
8
Department of Biochemistry& Molecular ChemistryDoshisha UniversityThe Hitomi Group
[Fe(dpaqH)NCCH3]2+(ClO4)2 (1)
Formation of FeIIIOMe Complex
Wavelength (nm)
Et3N 1 eq.
MeOH, -40°C
FeN NN
O
NN
O +
H
CH3
The corresponding methoxoiron(III) complex was prepared by the addition of 1 eq. of base.
ESI-MSAbsorption spectra
Calcd for[Fe(dpaqH)OMe] +
[Fe(dpaqH)OMe] + (2)
Abs a
t 680
nm
[Base] / (1)
+ base
Yellowspecies
FeN NN
O
NN
N
(ClO4)2
C
H
CH32+
Abs
9
Department of Biochemistry& Molecular ChemistryDoshisha UniversityThe Hitomi Group
+ H2O2
Formation of FeIIIOOH species
FeN NN
O
NN
O+
H
OH
FeN NN
O
NN
O+
H
CH3
Wavelength (nm)
Fe(III)OOH was generated by addition of 100 eq. of H2O2.
Formation of [Fe(dpaqH)OOH]+ CSI-MS
Calcd for[Fe(dpaqH)OOH] +
ReddishPurple species
[Fe(dpaqH)OMe] + (2) [Fe(dpaqH)OOH] + (3)
Abs a
t 530
nm
Time / sec
Abs
H2O2 100eq.
MeOH, -40°C
10
Department of Biochemistry& Molecular ChemistryDoshisha UniversityThe Hitomi Group
EPR spectra of FeIIIOOH
2.13
2.52
2.28
1.88
1.96
2.16
X-band EPR spectra of Fe-OMe (2) and Fe-OOH (3) in CH3OH. Frequency, 9.12GHz; power, 5 mW : temperature, 77 K.
[FeIII(BLM)OH][FeIII(BLM)OOH][FeIII(dpaqH)OMe]+(2)[FeIII(dpaqH)OOH]+(3)
2.402.262.522.28
2.172.172.132.16
1.891.941.881.96
complex gy gx gz
The g values are similar to those reported for ABLM.
[Fe(dpaqH)OMe] + (2)
[Fe(dpaqH)OOH] + (3)
11
Department of Biochemistry& Molecular ChemistryDoshisha UniversityThe Hitomi Group
Griffith-Taylor AnalysisEPR Data for Low Spin Fe-OOH Complex
[FeIII(N4PY)OOH]2+
[FeIII(Py5)OOH]2+
[FeIII(tmpy)OOH]2+
[FeIII(TPA)(S)OOH]2+
[FeIII(PMA)OOH]+
[FeIII(BLM)OOH][FeIII(PaPy3)OOH]+
[FeIII(dpaqOMe)OOH]+
[FeIII(dpaqH)OOH]+
[FeIII(dpaqCl)OOH]+
[FeIII(dpaqNO2)OOH]+
2.172.152.192.192.272.262.242.2752.282.2662.266
2.122.132.122.152.182.172.142.1592.1632.1512.14
1.981.981.951.971.931.941.961.9541.9551.9511.954
complex gy gx gz
The complexes with anionic ligands show smaller Δ values than those with neutral ligands.
dyz
dxz
dxy
|V||Δ|Splitting of the T2gorbitals
due to distortions.
M. Martinho et al., Inorg. Chem. 2007, 46, 1709–1717.
8.00 9.00
10.00
11.00
12.00
13.00
14.00
15.00 0
1
2
3
4
5
6
NeutralFedpaqRFePaPy3ABLMPMAH
-Δ/λ
V/λ
Neutral Ligands
Anionic Ligands
12
Department of Biochemistry& Molecular ChemistryDoshisha UniversityThe Hitomi Group
8.00 9.00
10.00
11.00
12.00
13.00
14.00
15.00 0
1
2
3
4
5
6
NeutralFedpaqRFePaPy3ABLMPMAH
Griffith-Taylor Analysis
The OMe derivative showed the smallest |Δ| value in the iron-dpaq series.
dpaq series
Fe
OHdxyO
gxgz
gy
xz
y
EPR Data for Low Spin Fe-OOH Complex
[FeIII(N4PY)OOH]2+
[FeIII(Py5)OOH]2+
[FeIII(tmpy)OOH]2+
[FeIII(TPA)(S)OOH]2+
[FeIII(PMA)OOH]+
[FeIII(BLM)OOH][FeIII(PaPy3)OOH]+
[FeIII(dpaqOMe)OOH]+
[FeIII(dpaqH)OOH]+
[FeIII(dpaqCl)OOH]+
[FeIII(dpaqNO2)OOH]+
2.172.152.192.192.272.262.242.2752.282.2662.266
2.122.132.122.152.182.172.142.1592.1632.1512.14
1.981.981.951.971.931.941.961.9541.9551.9511.954
complex gy gx gz
dyz
dxz
dxy
|Δ|
|V|-Δ/λ
V/λ
R = NO2
R = HR = OMe
R = Cl
13
Department of Biochemistry& Molecular ChemistryDoshisha UniversityThe Hitomi Group
Theoretically Optimized Structures of FeIIIOOH
The Fe–O bond and the O–O bond increase in length as the substituent becomes electron donating.
Δ/λ Hammett Fe-O O-O Fe- N_quinoline
Fe-N_pyridine
Fe-N_aliphatic
Fe-N_pyridine Fe-N_amide Amide_N-C Amide_C=O
OMe -9.2 -0.268 180.9 148.9 196.2 198.2 201.6 199.4 195.1 134.7 124.8
H -9.3 0 180.8 148.6 196 198.3 201.6 199.3 195.4 135.1 124.5
Cl -9.5 0.227 180.8 148.5 196.1 198.4 201.5 199.4 195.2 135.3 124.4
NO2 -10 0.778 180.6 147.9 195.9 198.4 201.2 199.5 195 136.7 123.7
Fe–O
(nm
)
-Δ/λ
O–O
(nm
)R = NO2
R = H
R = Cl
R = OMe
BP86/TZV(2pf)/COSMO(MeOH)
14
Department of Biochemistry& Molecular ChemistryDoshisha UniversityThe Hitomi Group
Substituent Effect
FeN NN
O
NN
O+
OMe
OH
Stability?
Electron withdrawing
FeN NN
O
NN
O+
H
OH
FeN NN
O
NN
O+
Cl
OH
FeN NN
O
NN
O+
NO2
OH
15
Department of Biochemistry& Molecular ChemistryDoshisha UniversityThe Hitomi Group
Formation of FeIIIOOH species
FeIIIOOH species was generated by the addition of H2O2 (100 equiv.).
FeN NN
O
NN
O+
R
OH
FeN NN
O
NN
O+
R
CH3
H2O2 100eq.
MeOH, -40°CFeN NN
O
NN
N
C
2+CH3
(ClO4)2R
Et3N 1 eq.
MeOH, -40°C
Wavelength (nm)
Abs
R = NO2
R = Cl
R = OMe
R = H
535 nm
530 nm
540 nm
560 nm
16
Department of Biochemistry& Molecular ChemistryDoshisha UniversityThe Hitomi Group
Stability of Fe(III)OOH Species
NO2
ClOMe
H
Time / sec
The Fe(III)OOH species become more stable as the substituent becomes electron withdrawing.
Wavelength (nm)
Abs
Abs
FeN NN
O
NN
O+
R
OH
FeN NN
O
NN
O+
R
CH3
H2O2 100eq.
MeOH, -40°CFeN NN
O
NN
N
C
2+CH3
(ClO4)2R
Et3N 1 eq.
MeOH, -40°C
17
Department of Biochemistry& Molecular ChemistryDoshisha UniversityThe Hitomi Group
Conclusion
FeN
NO
NN
N
OOH
III
OMe
FeN
NO
NN
N
OOH
III
H
FeN
NO
NN
N
OOH
III
Cl
FeN
NO
NN
N
OOH
III
NO2
Electron withdrawing
Stability
H-atom abstraction?
18
Supporting Information
Department of Biochemistry& Molecular ChemistryDoshisha UniversityThe Hitomi Group
Griffith-Taylor AnalysisEPR Data for Low Spin Fe-OOH Complex
[FeIII(N4PY)OOH]2+
[FeIII(Py5)OOH]2+
[FeIII(tmpy)OOH]2+
[FeIII(TPA)(S)OOH]2+
[FeIII(PMA)OOH]+
[FeIII(BLM)OOH][FeIII(PaPy3)OOH]+
[FeIII(dpaqOMe)OOH]+
[FeIII(dpaqH)OOH]+
[FeIII(dpaqCl)OOH]+
[FeIII(dpaqNO2)OOH]+
2.172.152.192.192.272.262.242.2752.282.2662.266
2.122.132.122.152.182.172.142.1592.1632.1512.14
1.981.981.951.971.931.941.961.9541.9551.9511.954
complex gy gx gz
The number of the pyridines bond to FeIII are over 4.
Neutral Ligandsdyz
dxz
dxy
|V|
|Λ|
Splitting of the T2gorbitals due to distortions.
NNN
NN
NMeO OMe
N NNN
N4Py
Py5
19
Department of Biochemistry& Molecular ChemistryDoshisha UniversityThe Hitomi Group
Griffith-Taylor AnalysisEPR Data for Low Spin Fe-OOH Complex
[FeIII(N4PY)OOH]2+
[FeIII(Py5)OOH]2+
[FeIII(tmpy)OOH]2+
[FeIII(TPA)(S)OOH]2+
[FeIII(PMA)OOH]+
[FeIII(BLM)OOH][FeIII(PaPy3)OOH]+
[FeIII(dpaqOMe)OOH]+
[FeIII(dpaqH)OOH]+
[FeIII(dpaqCl)OOH]+
[FeIII(dpaqNO2)OOH]+
2.172.152.192.192.272.262.242.2752.282.2662.266
2.122.132.122.152.182.172.142.1592.1632.1512.14
1.981.981.951.971.931.941.961.9541.9551.9511.954
complex gy gx gz
The number of the pyridines bond to FeIII are less 3.
Neutral LigandsN
N
N
N
TPA
Trispicen
N N
N N
HN
Fe
OHdxyO
gxgz
gy
xz
y
20
Department of Biochemistry& Molecular ChemistryDoshisha UniversityThe Hitomi Group
Griffith-Taylor AnalysisEPR Data for Low Spin Fe-OOH Complex
[FeIII(N4PY)OOH]2+
[FeIII(Py5)OOH]2+
[FeIII(tmpy)OOH]2+
[FeIII(TPA)(S)OOH]2+
[FeIII(PMA)OOH]+
[FeIII(BLM)OOH][FeIII(PaPy3)OOH]+
[FeIII(dpaqOMe)OOH]+
[FeIII(dpaqH)OOH]+
[FeIII(dpaqCl)OOH]+
[FeIII(dpaqNO2)OOH]+
2.172.152.192.192.272.262.242.2752.282.2662.266
2.122.132.122.152.182.172.142.1592.1632.1512.14
1.981.981.951.971.931.941.961.9541.9551.9511.954
complex gy gx gz
Amidate Ligands are comparative weaker Δ value than Neutral Ligands.
Amidate Ligands
PaPy3-H
N
ON
HN
N
N
NH2
H2NOC
NH
FeN
NO
N
N
N
O
O
H2NOC
H2N
Activated bleomycin
H
CH3
OOH
21
Department of Biochemistry& Molecular ChemistryDoshisha UniversityThe Hitomi Group
|∆| value
The more accepting the FeIII is, the stronger the interaction is with the donor ⃰ antibonding orbital of the hydroperoxo group and the larger is |Λ|
dyz
dxz
dxy
|Λ|
|V|
larger |∆|
intermediate value of |∆|
smaller |∆|
(1) at least 4 pyridine groups
(2) 3 pyridine groups
(3) amidate coordination
(1)
(2)
(3)
22
Fe
OHdxyO
gxgz
gy
xz
y
Department of Biochemistry& Molecular ChemistryDoshisha UniversityThe Hitomi Group
UV-Vis spectram of FeOOH
The maximum absorption wavelength is slightly difference.
FeN NN
O
NN
O+
R
OH
FeN NN
O
NN
O+
R
CH3
H2O2 100eq.
MeOH, -40°C
FeN NN
O
NN
N
C
2+
CH3
(ClO4)2R
Et3N 1 eq.
MeOH, -40°C
OMe Cl
NO2
Wavelength (nm)
Abs
Wavelength (nm)Ab
s
Wavelength (nm)
Abs
560 nm 540 nm
535 nm
Wavelength (nm)
Abs
H
530 nm
23
Department of Biochemistry& Molecular ChemistryDoshisha UniversityThe Hitomi Group
Proposal
OOH
Fe
N
d-weak
strong
p-pushAmidate coordination
FeD
N
B
AC
OOH
III
O
heterolysis
s*
dp
2e-
Amidate coordination is expected to work as a "p-push" donor to promote heterolysis of the O−O bond.
OOH
Fe
O
Fe
OH
III V
O
Feheterolysis V
OH
K. Yamaguchi, Y. Watanabe, I. Morishima, J. Am. Chem. Soc. 1993, 115, 4058.
24
III
Department of Biochemistry& Molecular ChemistryDoshisha UniversityThe Hitomi Group
Generation of [FeIII(dpaq)OOH]+
IIIN
FeNN
NN
O
Cl
[FeIII(dpaq)Cl]+
in MeCN at -40 °C
100 eq. of H2O2
[FeIII(dpaq)OOH]+
IIIN
FeNN
NO
ON
OH
Fe-OOH species can be generated from Fe-OMe complex.
[FeIII(dpaq)OMe]+ [FeIII(dpaq)OOH]+
IIIN
FeNN
NO
OMe
N IIIN
FeNN
NO
ON
OH
in MeOH at -40 °C
100 eq. of H2O2
in MeOH1 eq. of Et3N
26
Department of Biochemistry& Molecular ChemistryDoshisha UniversityThe Hitomi Group EPR specrum of a series of Fe
dpaqOOH
Cl
H
NO2
OMe
2.275
2.159
1.954
2.28
2.163
1.955
2.266 2.151
1.951
2.2662.14
1.954
26
Department of Biochemistry& Molecular ChemistryDoshisha UniversityThe Hitomi Group
FeOOH MO diagram
-7.0
-6.5
-6.0
-5.5
-5.0
-4.5
-4.0
-3.5
-3.0
-2.5
-2.0
OMe H Cl NO2
Ener
gy/ e
V
The LMCT hydroperoxo–FeIII band was calculated by DFT.
OMeHCl
NO2
Cal.
0.802 eV0.915 eV0.909 eV0.977 eV
LMCTLMCT
LMCTLMCT
α spin
β spin
α spin
β spin
α spin
β spin
α spin
β spin
27
Department of Biochemistry& Molecular ChemistryDoshisha UniversityThe Hitomi Group
FeOOH MO diagram
-7.0 -6.5 -6.0 -5.5 -5.0 -4.5 -4.0 -3.5 -3.0 -2.5 -2.0
FeN
NO
NN
N
OOH
III
OMe
FeN
NO
NN
N
OOH
III
H
FeN
NO
NN
N
OOH
III
Cl
FeN
NO
NN
N
OOH
III
NO2
α spin
β spin
α spin
β spin
α spin
β spin
α spin
β spin
Ener
gy/ e
V28
Department of Biochemistry& Molecular ChemistryDoshisha UniversityThe Hitomi Group
Redox PotentialE
。(m
V vs
. Fc+ /
Fc )
para
R = NO2
R = H
R = Cl
R = OMe
As the substituent group becomes more electron-donating, the redox potentials become more negative.
Department of Biochemistry& Molecular ChemistryDoshisha UniversityThe Hitomi Group
Role of conjugate acid
Does the conjugate acid promote cleavage of the O−O bond, like the distal His residue of horseradish peroxidase?
facilitate?
FeN
N
N
NNV
O
N
R
H2O
FeN
N
N
NN
OOH
III
N
R
H
conjugate acid
Horseradish Peroxidaseconjugate acid
Pull effect
29
Department of Biochemistry& Molecular ChemistryDoshisha UniversityThe Hitomi Group
Effect of conjugate acid
red : Et3Nblue : 2, 4, 6 Collidineburaun : Lutidine
Abs
at 5
30 n
m
FedpaqH
1. base 1 eq. 2. H2O2 200eq.
MeOH, -40°CFeOOH
Time / sec
The conjugate acids accelerate cleavage of the O−O bond.
N
H
H
NH
N
CH3
H
fast decay of Fe(III)OOH
strong proton donor
Max
imum
Abs
. int
ensi
ty a
t 530
nm
pka value of conjugate acid
30
Department of Biochemistry& Molecular ChemistryDoshisha UniversityThe Hitomi Group
Decay of FeIIIOOH species
0.4
0.3
0.2
0.1
0.0
Abs
orba
nce
1000900800700600500400 Wavelength / nm
?Species X
ESI-MS
488486484482480 m / z
0.3
0.2
0.1
0.0
Abs
orba
nce
400020000
Time / sec
680 nm
530 nm530 nm
680 nm
Formation of a new species
530 nm
The decay of the Fe(III)OOH resulted in the formation of a new species.
Calcd for
[Fe(dpaq)] + + 45
FeN NN
O
NN
O+
H
OH
FeN NN
O
NN
O+
H
CH3
[Fe(dpaqH)OMe] + (2)[Fe(dpaqH)OOH] + (3)
H2O2 100eq.
MeOH, -40°C
680 nm
31
Department of Biochemistry& Molecular ChemistryDoshisha UniversityThe Hitomi Group
Decay of FeIIIOOH species
0.4
0.3
0.2
0.1
0.0
Abs
orba
nce
1000900800700600500400 Wavelength / nm
ESI-MS
488486484482480 m / z
0.3
0.2
0.1
0.0
Abs
orba
nce
400020000
Time / sec
680 nm
530 nm530 nm
680 nm
Formation of a new species
The new species is a formate adduct.
Calcd for
[Fe(dpaq)] + + 45
FeN NN
O
NN
O+
H
OH
FeN NN
O
NN
O+
H
CH3
[Fe(dpaqH)OMe] + (2)[Fe(dpaqH)OOH] + (3)
H2O2 100eq.
MeOH, -40°C
[Fe(dpaqH)HCO2]+ (4)
FeN NN
O
NN
O+
H
CO
H
680 nm
32
Department of Biochemistry& Molecular ChemistryDoshisha UniversityThe Hitomi Group
Identification of species X
ESI-MS
490488486484482480 m / z
502500498496494 m / z
formed in CD3OD
ESI-MS
formed in EtOH
Calcd for
[Fe(dpaq)] + + 46Calcd for
[Fe(dpaq)] + + 59
FeN
NO
NN
N
OOH
III
+
FeN
NO
NN
N
O
III
+
O
H
[Fe(dpaq)OOH]+ (3) [Fe(dpaq)HCO2]+ (4)
Oxidation of MeOH
The coordinated acid came from oxidized solvent.
FeN NN
O
NN
O+
H
CO
CH3
FeN NN
O
NN
O+
H
CO
D
33
Department of Biochemistry& Molecular ChemistryDoshisha UniversityThe Hitomi Group
Proposed Reaction Cycle
FeN
NO
NN
N
OCH3
III
H 2+Fe
NNO
NN
N
OCH3
III
+
FeN
NO
NN
N
OOH
III
+
FeN
NO
NN
N
O
III
+
O
H
+ H2O2
− MeOH
+ Base
− BaseH+
− H2O
+ MeOH
MeOH
HCO2H
H2O + HCHO
+ BaseH+
− MeOH
FeN
NO
NN
N
O
IV
+
− H+
S = 3/2
Spin density map
34
Department of Biochemistry& Molecular ChemistryDoshisha UniversityThe Hitomi Group
Formation of Methoxido Complex
Wavelength (nm)
Abs
orba
nce
Et3N 3 eq.
MeOH, -40°C
FeN NN
O
NN
Cl +
H Cl
FeN NN
O
NN
O +
H
CH3
The OMe complex was prepared by addition of 3 eq. of base.
ESI-MSAbsorption spectra
Calcd for[Fe(dpaqH)OMe] +
[Fe(dpaqH)Cl]+Cl (1) [Fe(dpaqH)OMe] + (2)
Abs
at 6
80 n
m
[Base] / (1)
+ base
Yellowspecies
35
Department of Biochemistry& Molecular ChemistryDoshisha UniversityThe Hitomi Group
Formation of Fe(III)OOH species
FeN NN
O
NN
O+
H
OH
FeN NN
O
NN
O+
H
CH3
Wavelength (nm)
Abs
orba
nce
Fe(III)OOH was generated by addition of 100 eq. of H2O2.
Formation of [Fe(dpaqH)OOH]+ CSI-MS
Calcd for[Fe(dpaqH)OOH] +
ReddishPurple species
[Fe(dpaqH)OMe] + (2) [Fe(dpaqH)OOH] + (3)A
bs a
t 530
nm
Time / sec+ H2O2
H2O2 100 eq.
MeOH, -40°C
36
Department of Biochemistry& Molecular ChemistryDoshisha UniversityThe Hitomi Group
Formation of Methoxido Complex
Wavelength (nm)
Abs
orba
nce
Et3N 3 eq.
MeOH, rt
FeN NN
O
NN
Cl +
H Cl
FeN NN
O
NN
O +
H
CH3
The OMe complex was also prepared, and stable at room tempature.
ESI-MSAbsorption spectra
Calcd for[Fe(dpaqH)OMe] +
[Fe(dpaqH)Cl]+Cl [Fe(dpaqH)OMe] + (2)
Abs
at 6
80 n
m
[Base] / (1)
+ base
Yellowspecies
37
Department of Biochemistry& Molecular ChemistryDoshisha UniversityThe Hitomi Group
Formation of Fe(III)OOH species
FeN NN
O
NN
O+
H
OH
FeN NN
O
NN
O+
H
CH3
Wavelength (nm)
Abs
orba
nce
Fe(III)OOH was very unstable at room tempataure.
Formation of [Fe(dpaqH)OOH]+
ReddishPurple species
[Fe(dpaqH)OMe] + (2) [Fe(dpaqH)OOH] + (3)
Abs
at 5
30 n
m
Time / sec
+ H2O2
Decay of [Fe(dpaqH)OOH]+
H2O2 100 eq.
MeOH, rt
38
Department of Biochemistry& Molecular ChemistryDoshisha UniversityThe Hitomi Group
Push Effect on the Stability of Fe(III)OOH Species
Push Push
FeN
NO
NN
N
OOH
IIIFeN
NO
NN
N
OOH
III
Heterolysis? Homolysis?
Can the amidate coordination induce heterolysis of the O−O bond?
Which?
39
Department of Biochemistry& Molecular ChemistryDoshisha UniversityThe Hitomi Group
Differential pulse voltammograms
Differential pulse voltammograms of FeIII(dpaqR ) in MeCN/H2O (9:1).
Hitomi, Y.; Arakawa, K.; Kodera, M. Chem. Eur. J. 2013, 19, 14697–14701.
OMeHCl
NO2
100 mV 71 mV 22 mV 85 mV
E1/2
40
FeOOH_dpaq_OMe_orbital (#127b-130b)
127128
129130
#127 #128
#129 #130
FeOOH_dpaq_H_orbital (#119b-122b)
119120
121122
#119 #120
#121 #122
FeOOH_dpaq_H_orbital (#119b-122b)
119120
121122
#119 #120
#121 #122
FeOOH_dpaq_NO2_orbital (#130b-133b)
130131
132133
#130 #131
#132 #133