3046
J. A m . Chem. SOC.1984, 106, 3046-3047
respectively, of ferryltetraphenylporphyrin, OFe(TPP), which is formed by the cleavage of dioxygen of Fe(TPP)02 via laser photolysis. The observed isotopic shift (852 - 818 = 34 cm-I) is in good agreement with that expected for a perturbed FeO molecule (38 cm-I). These bands cannot be attributed to the pox0 dimer, (Fe(TPP)),O, since no strong Raman bands are seen near 360 ~ m - l . ~ Further support for our conclusion is provided by NAFe-54Fe isotope substitution. As are shown by the broken lines of Figure 1, A and B, the bands at 852 and 8 18 cm-' of I6ONAFe(TPP)and I8ONAFe(TPP),respectively, are shifted by 4.0 cm-' to higher frequencies by the substitution, and these values are again in good agreement with those expected for a perturbed FeO molecule (3.5 cm-I). A simple diatomic approximation gives a force constant of 5.32 mdyn/A for the above ferryl group. This is much larger than that of the Fe-0 bonds in (Fe(TPP))20 (3.8 m d ~ n / A and ) ~ in oxyhemoglobin (3.09 mdyn/A).5.6 In this respect, the formulas such as PFeIV=02- or PFev==02- describe the ferryl group better or PFeIV-0- (P: porphyrin). than PFe"'-0According to recent a b initio MO calc~lations,~ the negative charge and polarization of the dioxygen greatly increase upon coordination to an iron porphyrin (Le., Fe-O1(-0.46e)-O2(0.19e)). This trend will be accelerated by the donation of the second electron from NADH to the iron center and the presence of a cysteinyl sulfur (S-) a t the trans position to the dioxygen in cytochrome P-450. It is then not surprising that the 0-0 bond cleavage occurs quite easily under biological conditions. We are now conducting experiments to answer the question of whether we can mimic the hydroxylation reaction of cytochrome P-450 in a matrix environment.
Acknowledgment. This work was supported by a National Science Foundation Grant (PCM-8114676). (4) Burke, J. M.; Kincaid, J. R.; Spiro, T. G. J . Am. Chem. Soc. 1978,100, 6077. (5) Duff, L. L.; Appelman, E. H.; Shriver, D. F.; Klotz, I. M. Biochem. Biophys. Res. Commun. 1979, 90, 1098. (6) Duff-Weddell, L. L. Ph.D. Thesis, Northwestern University, Evanston, IL, 1981. (7) Nozawa, T.; Hatano, M.; Nagashima, U.; Obara, S.; Kashiwagi, H . Bull. Chem. SOC.Jpn. 1983, 56, 1721.
Scheme la
4-ZE
Id
4-E2
CHjOZC
5-EZ
95%
Q
0
(a) NaH/THT; (b) ( C , H , ) , P = C H C O C H , , (c) ( C 6 H 5 ) 3 P = CHCO,CH,/THT; (d) f-C,H,OH/l N NaOH ( l : l O ) , 0 "C, 4 min; a
(e) I , / T H I , reflux.
the enzyme's ~ u r f a c e . ~In the enzymatic and nonenzymatic reaction, reversible nucleophilic addition of GSH to C2 of 1 forming a dienediol intermediate (3) thereby allows internal rotation about the C2
