7142
J. Am. Chem. Soc. 2000, 122, 7142-7143
complexes (M ) Ni),15 this is also the first observation of
First Observation of Photoinduced Nitrosyl Linkage
Isomers of Iron Nitrosyl Porphyrins
photoinduced nitrosyl linkage isomerism for a bent nitrosyl
7
{
MNO} complex of any metal.
Irradiation of the Fe(por)(NO) compounds16 (as KBr pellets)
§
†
†
Lin Cheng, Irina Novozhilova, Chris Kim,
at 25 K for 5-10 min results in the formation of new bands in
their IR spectra, downshifted from the parent NO stretching
frequencies. The observed frequencies of the photoinduced bands
†
,‡
Andrey Kovalevsky, Kimberly A. Bagley,*
Philip Coppens,* and George B. Richter-Addo*
,†
,§
for the 14N O, N O and N O complexes of Fe(OEP) and
Fe(TTP) and their relative shifts are listed in the Supporting
Information. Warming the samples to 40 K results in the
disappearance of all new bands and the restoration of the
intensities of the parent υNO bands. No free NO was observed in
the photolysis experiments.
16
15 16
15 18
Department of Chemistry
State UniVersity of New York at Buffalo
Buffalo, New York 14260-3000
Department of Chemistry
State UniVersity College of New York at Buffalo
Buffalo, New York, 14222
Department of Chemistry and Biochemistry
UniVersity of Oklahoma, 620 Parrington OVal
Norman, Oklahoma, 73019
In the case of Fe(TTP)(NO), photolysis at 25 K for 10 min
-
1
results in the appearance of a new band at 1532 cm in the
difference IR spectrum (A in Figure 1, left), downshifted by ∼140
-
1
15 16
cm . Measurements on isotope-labeled Fe(TTP)( N O) and Fe-
15
18
ReceiVed April 10, 2000
(TTP)( N O) show the band to be due to the coordinated NO
group (Figure 1; Table S1 of the Supporting Information). A
second, much weaker, photoinduced band at 1502 cm does not
Knowledge of the binding modes of nitric oxide (NO) to
synthetic iron porphyrins is essential to an overall understanding
of the action of NO-heme-containing biomolecules, which play
-1
change on isotopic substitution (Figure 1, left), and is hence
assigned as originating from another part of the complex. Because
of the rapid decay of the photoinduced IR features, samples were
irradiated continuously during the spectral measurements.
A similar IR band (A in Figure 1, right) is generated when
Fe(OEP)(NO) is irradiated under the same conditions. The use
1
a crucial role in several biologically important processes. While
much is known about the biological effects of NO, the detailed
mechanism of NO uptake and release by the heme group remains
to be elucidated. Kinetic studies of photochemically induced loss
2,3
and recombination of NO with hemoproteins and metallopor-
phyrins4 suggest that recombination after photolysis is a fast and
multistage process at room temperature.6
of the 15N O and N O isotope labels again reveals the band to
16
15 18
,5
be due to the coordinated NO group. However, a second new IR
-8
-
1
band at 1520 cm (labeled B) is also induced, together with an
Known geometries of FeNO linkages in iron porphyrins and
heme have, to date, been limited to the Fe-N-O arrangement
-
1
isotope-substitution insensitive band at 1506 cm (Figure 1,
right). While both the A and B bands decay at 25 K, the decay
of the B band is much slower, suggesting the formation of two
distinct photoproducts. The isotopic shifts of the IR bands are as
9
in linear or bent forms. In general, iron nitrosyl porphyrins of
6
the “ferric” {FeNO} formulation have linear Fe-N-O groups,
7
whereas those of the “ferrous” {FeNO} formulation have bent
15
16
expected for Fe(OEP)( N O) and its photoproducts, and for the
Fe-N-O groups. We have recently reported that photoexcitation
15
18
Fe(OEP)( N O) derivative and its A photoproduct. The B band
6
of {RuNO} ruthenium nitrosyl porphyrins results in the formation
15
18
of photolyzed Fe(OEP)( N O) appears as a doublet and the shift
1
2
of metastable O-bound (η -O; MS1) and side-on (η -N,O; MS2)
-
1
-1
of ∼95 cm is larger than the expected value of ∼68 cm .
Vibrational coupling of this low-frequency band with other modes
of the complex may be responsible for the latter observation.
Conversion percentages are estimated at 6-10% for Fe(OEP)-
bound linkage isomers.10 We now report that metastable NO
linkage isomers of {FeNO} iron nitrosyl porphyrins are generated
7
upon illumination with light of 350 < λ < 550 nm wavelength
(
300 W xenon arc lamp). While NO linkage isomers have been
(
NO), and 2-3% for Fe(TTP)(NO).
6
11-14
10
observed for {MNO} (M ) Fe, Ru, Os)
and for {MNO}
The observed shifts of υNO for the Fe(por)(NO) photoproducts
†
Department of Chemistry, State University of New York at Buffalo,
Buffalo, New York 14260-3000.
are very similar to those recorded for other non-porphyrin Fe and
Ru complexes for which the identity of the photoinduced species
‡
Department of Chemistry, State University College of New York at
1
1-14
have been established by photocrystallographic experiments.
Buffalo, Buffalo, New York, 14222.
§
1
University of Oklahoma.
1) Cheng, L.; Richter-Addo, G. B. Binding and Activation of Nitric Oxide
The IR data thus suggests the formation of an MS1 (η -ON)
isomer upon irradiation. This assignment is supported by the DFT
calculations.
(
by Metalloporphyrins and Heme. In The Porphyrin Handbook; Kadish, K.
M., Smith, K. M., Guilard, R., Eds.; Academic Press: New York, 2000; Vol.
4
(Biochemistry and Binding: Activation of Small Molecules), pp 219-291.
A series of theoretical calculations was performed on FeP′-
(
2) Walda, K. N.; Liu, X. Y.; Sharma, V. S.; Magde, D. Biochemistry 1994,
3, 2198-2209.
3) Carlson, M. L.; Regan, R.; Elber, R.; Li, H.; Phillips, G. N.; Olson, J.
(
NO) (P′ ) porphine dianion) with the Amsterdam Density
3
17,18
(
Functional (ADF) package.
S.; Gibson, Q. H. Biochemistry 1994, 33, 10597-10606; Olson, J. S.; Phillips,
The ground-state optimization of FeP′(NO) reproduces the
structural distortions of the N Fe(NO) core recently observed by
G. N. J. Biol. Chem. 1996, 271, 17593-17596.
(
4) Zavarine, I. S.; Kini, A. D.; Morimoto, B. H.; Kubiak, C. P. J. Phys.
4
Chem. B 1998, 102, 7287-7292.
(
(
5) Morlino, E. A.; Rodgers, M. A. J. Am. Chem. Soc. 1996, 118, 11798.
6) Ford, P. C.; Bourassa, J.; Miranda, K.; Lee, B.; Lorkovic, I.; Boggs,
(13) Coppens, P.; Fomitchev, D. V.; Carducci, M. D.; Culp, K. J. Chem.
Soc., Dalton Trans. 1998, 865-872.
S.; Kudo, S.; Laverman, L. Coord. Chem. ReV. 1998, 171, 185-202.
(14) Fomitchev, D. V.; Coppens, P. Comments Inorg. Chem. 1999, 21,
131-148.
(
7) Hoshino, M.; Laverman, L.; Ford, P. C. Coord. Chem. ReV. 1999, 187,
7
5-102.
(15) Fomitchev, D. V.; Furlani, T. R.; Coppens, P. Inorg. Chem. 1998, 37,
1519-1526.
(
8) Morlino, E. A.; Rodgers, M. A. J. Prog. React. Kinet. 1998, 23, 91-
1
15.
(16) The five-coordinate nitrosyl iron porphyrins were prepared using
established procedures (ref 1) by reacting Fe(OEP)Cl and Fe(TPP)Cl (OEP
) octaethylporphyrinato dianion; TTP ) tetratolyporphyrinato dianion) with
NO gas in chloroform followed by addition of methanol.
(17) The Amsterdam Density Functional program package, v.1999.02; the
Vrije Universiteit: Amsterdam; the University of Calgary: Canada. Fonseca
Guerra, C.; Visser, O.; Snijders, J. G.; te Velde, G.; Baerends, E. J. In Methods
and Techniques for Computational Chemistry (METECC-5); Clementi, E.,
Corongiu, G., Eds.; STEF: Cagliari, 1995; pp 303-395.
(
9) For a listing of crystallographically characterized nitrosylmetallopor-
phyrins and nitrosyl hemes, see Table 6 in ref 1. See Tables 9 and 10 in ref
for a listing of known iron nitrosyl porphyrins.
10) Fomitchev, D. V.; Coppens, P.; Li, T.; Bagley, K. A.; Chen, L.;
Richter-Addo, G. B. Chem. Commun. 1999, 2013-2014.
11) Carducci, M. D.; Pressprich, M. R.; Coppens, P. J. Am. Chem. Soc.
997, 119, 2669-2678.
12) Fomitchev, D. V.; Coppens, P. Inorg. Chem. 1996, 35, 7021-7026.
1
(
(
1
(
1
0.1021/ja001243u CCC: $19.00 © 2000 American Chemical Society
Published on Web 07/07/2000