BIOINORGANIC CHEMISTRY A Short Course Second Edition

442 IRON-CONTAINING PROTEINS AND ENZYMES

See 3.7.3 for a discussion of the MALDI – TOF mass spectrometric method.
Resonance Raman spectroscopy identifi ed a peroxo stretching vibration
ν (O – O) at 808 cm − 1. The resonance was confi rmed by testing an^18 O 22 − complex,
resulting in a− 46 cm − 1 change in the vibration frequency. Solution magnetic
moment measurements and^1 H NMR indicated an S = 2 spin state for the
complex that would arise from antiferromagnetic coupling between high - spin
Fe(III) and Cu(II) centers (see Figure 7.45 ).
M ö ssbauer spectroscopy yielded data consistent with a high - spin Fe(III)
ion possessing a peroxide ligand: ΔEQ = 1.14 mm/s and δ = 0.57 mm/s. Stopped -
fl ow UV – visible spectroscopy indicated that a heme – superoxide intermediate
[( ) (−− 82 ) III ( −⋅)] SFTPPFe O ( λmax = 537 nm, S = solvent) is generated within ∼ 1 ms
(the mixing time) before the [( 82 ) III−−(^2 −+) II( )] F TPP Fe complex O Cu TMPA
(λmax = 556 nm) forms. The same [( 82 ) III−−(^2 −+) II( )] F TPP Fe complex O Cu TMPA
has been generated from alternate starting materials: [( 82 ) III−(^21 −−)] F TPP Fe O
and [Cu II (TMPA)(MeCN)] 2+.^152 More recently, Karlin, E. I. Solomon, and
co - workers have studied the geometric and electronic structure of
( 82 ) III−−(^2 −) II( ) F TPP Fe using Cu and Fe K - edge EXAFS O Cu TMPA ClO

Figure 7.44 Cytochrome c oxidase model complexes, [( 82 ) III−−(^2 −) F TPP FeII O Cu
()]TMPA+, as synthesized in reference 151.

+

N N

F N FeII

F ArF

N

F

F

ArF

N

N

N

CuI

N

+

O 2

• 40o C, MeCN

+

N N

N FeII

F

F ArF

N

N

CuI

N

N

(O 2 2-)

N

F

F

ArF

2 +

N N

N FeII

F

F ArF

N

N

CuI

N

N

(OH)

N

F

F

ArF

F

F

N N

F N FeII

F ArF

N

N

CuI

N

N

(O)

N

F

F

ArF

+

ΔT

0.5 mol O 2

H+

= ArF

[(F 8 TPP)FeIII-(O 2 2-)-CuII(TMPA)]+

[(F 8 TPP)FeIII-(OH-)-CuII(TMPA)]2+ [(F 8 TPP)FeIII-(O2-)-CuII(TMPA)]+