BIOINORGANIC CHEMISTRY A Short Course Second Edition

Table 3.2 lists values for ΔEQ and δ for some important oxidation and spin

states found in bioinorganic molecules. Data are taken from reference 34 and

from Table 1 of reference 35 for hemoglobin, Hb, myoglobin, Mb, and the

picket - fence porphyrin model compound, FeTpivPP(1 - MeIm).^35 The myoglo-

bin and hemoglobin model compounds are discussed in Sections 7.2.6 through

MÖSSBAUER SPECTROSCOPY 135

TABLE 3.2 M ö ssbauer Parameters for Some Biological Species a

Oxidation State Spin State Ligands ΔEQ (mm s − 1 ) δ (mm s − 1 )

Fe(IV) S = 2 Fe – (O, N) b 0.5 – 1.0 0.0 – 0.1
Fe(IV) S = 1 Hemes 1.0 – 2.0 0.0 – 0.1
Fe – (O, N) 0.5 – 4.3 − 0.20 – 0.10
Fe(III) S = 5/2 Hemes 0.5 – 1.5 0.35 – 0.45
Fe(III) S = 5/2 Fe – S c < 1.0 0.20 – 0.35
Fe(III) S = 5/2 [FeS 4 ] cluster
(rubredoxin)

0.25

Fe(III) S = 5/2 [Fe 2 S 2 ] 2+ cluster 0.27
Fe(III) S = 5/2 Fe(III) in [Fe 2 S 2 ] +
cluster

0.30

Fe(III) S = 5/2 [Fe 3 S 4 ] + cluster 0.27
Fe(III) S = 5/2 [Fe 3 S 4 ]^0 cluster 0.32
Fe(III) S = 5/2 Fe – (O, N) 0.5 – 1.5 0.40 – 0.60
Fe(III) S = 3/2 Hemes 3.0 – 3.6 0.30 – 0.40
Fe(III) S = 1/2 Hemes 1.5 – 2.5 0.15 – 0.25
Hb(O 2 ) e 2.19 0.26
FeTpivPP(1 - MeIm)
(O 2 ) d

2.04 0.27

Fe(III) S = 1/2 Fe – (O, N) 2.0 – 3.0 0.10 – 0.25
Fe(II) S = 2 Hemes 1.5 – 3.0 0.85 – 1.0
Hb e 2.22 0.92
Mb e 2.17 0.91
FeTpivPP(1 - MeIm) d 2.32 0.88
Fe(II) S = 2 Fe – S 0.0 – 3.0 0.60 – 0.70
Fe(II) S = 2 [FeS 4 ] cluster
(rubredoxin)

0.70

Fe(II) S = 2 Fe(II) in [Fe 2 S 2 ] +
cluster

0.72

Fe(II) S = 0 Fe – (O, N) 1.0 – 3.2 1.1 – 1.3
Fe(II) S = 0 Hemes < 1.5 0.30 – 0.45
Delocalized
Fe 2.5+ – Fe 2.5+

S = 1/2 or S = 9/2

coupled to S = 5/2

Fe 3+ site

[Fe 3 S 4 ]^0 0.46

a Typical values at 4.2 K. Isomer shifts are taken relative to the standard value for Fe metal at 298 K.
b Fe – (O, N) hexacoordinate or pentacoordinate sites.
c Fe – S tetrahedral sulfur ligation.
d TpivPP = 5, 10, 15, 20 - tetrakis - [ o - (pivalamido)phenyl]porphyrinate( 2 − ); 1 - MeIm = 1 - methylimidazole.
e Hb = hemoglobin, Hb(O 2 ) = dioxygenated hemoglobin, Mb = myoglobin.

Source : References 34 – 36.