I
n the further developme
nt a
nd u
ndersta
ndi
ng of heme-copper O
2-reductio
n chemistry i
nspired by the active-sitechemistry i
n cytochrome
c oxidase, we describe a dioxyge
n adduct, [(F
8TPP)Fe
III-(O
22-)-Cu
II(TMPA)](ClO
4) (
3),formed by additio
n of O
2 to a 1:1 mixture of the porphyri
nate-iro
n(II) complex (F
8TPP)Fe
II (
1a) {F
8TPP = tetrakis(2,6-difluorophe
nyl)porphyri
nate dia
nio
n} a
nd the copper(I) complex [(TMPA)Cu
I(MeCN)](ClO
4) (
1b) {TMPA = tris(2-pyridylmethyl)ami
ne}. Complex
3 forms i
n prefere
nce to heme-o
nly or copper-o
nly bi
nuclear products, is remarkablystable {
t1/2 (RT; MeCN)
ntities/ap.gif"> 20 mi
n;
max = 412 (Soret), 558
nm; EPR sile
nt}, a
nd is formulated as a peroxocomplex o
n the basis of ma
nometry {
1a/
1b/O
2 = 1:1:1}, MALDI-TOF mass spectrometry {
16O
2,
m/
z 1239 [(
3 +MeCN)
+];
18O
2,
m/
z 1243}, a
nd reso
na
nce Rama
n spectroscopy {
nu.gif" BORDER=0 >
(O-O) = 808 cm
-1;
16O
2/
18O
2 = 46 cm
-1;
16O
2/
16/18O
2 = 23 cm
-1}. Co
nsiste
nt with a
ntities/mgr.gif">-
2:
1 bridgi
ng peroxide liga
nd, two metal-O stretchi
ng freque
nciesare observed {
nu.gif" BORDER=0 >
(Fe-O) = 533 cm
-1,
nu.gif" BORDER=0 >
(Fe-O-Cu) = 511 cm
-1}, a
nd supporti
ng
normal coordi
nate a
nalysis is prese
nted.
2H a
nd
19F NMR spectroscopies reveal that
3 is high-spi
n {also
ntities/mgr.gif">
B = 5.1 ± 0.2, Eva
ns method} with dow
nfield-shifted pyrrole a
nd upfield-shifted TMPA reso
na
nces, similar to the patter
n observed for the structurally characterized
ntities/mgr.gif">-oxo complex [(F
8TPP)Fe
III-O-Cu
II(TMPA)]
+ (
4) (k
now
n S = 2 system, a
ntiferromag
netically coupled high-spi
nFe
III a
nd Cu
II). Mössbauer spectroscopy exhibits a sharp quadrupole doublet (zero field;
= 0.57 mm/s,
ntities/verbar.gif">
EQntities/verbar.gif"> =1.14 mm/s) for
3, with isomer shift a
nd mag
netic field depe
nde
nce data i
ndicative of a peroxide liga
nd a
nd
S =2 formulatio
n. Both UV-visible-
monitored stopped-flow ki
netics a
nd Mössbauer spectroscopic studies reveal theformatio
n of heme-o
nly superoxide complex (S)(F
8TPP)Fe
III-(O
2-) (
2a) (S = solve
nt
molecule) prior to
3. Thermaldecompositio
n of
ntities/mgr.gif">-peroxo complex
3 yields
ntities/mgr.gif">-oxo complex
4 with co
ncomita
nt release of ~0.5
mol O
2 per
mol
3. Characterizatio
n of the reactio
n 1a/
1b + O2 ntities/rarr.gif">
2 ntities/rarr.gif">
3 ntities/rarr.gif">
4, prese
nted here, adva
nces our u
ndersta
ndi
ng a
ndprovides
new i
nsights to heme/Cu dioxyge
n-bi
ndi
ng a
nd reductio
n.