8628
J . Am. Chem. SOC.1988, 110, 8628-8638
as evidenced by its change in color during the assay, thereby inhibiting the response at the QCM associated with reaction 2. Investigations with more inert supports are currently in progress. Concluding Remarks The results described above demonstrate that amplification routes via catalytic processes, such as enzymatic reactions, can significantly extend the detection limits of piezoelectric assay. Since antibodies can be elicited for a wide variety of analytes, the methodology can be generally applied to various substances (e.g. proteins, enzymes, hormones, etc.). The method requires, in addition to an antibody, only an appropriate anti-analyte-enzyme conjugate to convert the substrate to a product capable of inducing a mass change at the surface of the quartz crystal. Detection can be accomplished by simple deposition of insoluble assay products or by reactions of the assay products with films on the QCM that produce mass changes due to adsorption-complexation processes or changes in ion population. As demonstrated here, the latter
is particularly advantageous if reusable sensors are desired. One key advantage of enzymatically amplified sandwich methods is that detection limits are independent of the mass of the analyte. Therefore, detection of low molecular weight analytes such as hormones and drugs is possible under conditions where detection of direct binding will be difficult. The versatility regarding the ease of modification of the QCM surface makes piezoelectric detection widely applicable toward a variety of analytes and suggests that chemical design of new receptors on the surface of the QCM will play a significant role in expanding the scope of piezoelectric immunoassay. Acknowledgment. We thank J. M. Odom for preparation of the APS reductase antibody, S. Y . Tseng for preparation of the APS reductasealkaline phosphatase conjugate, and E. J. Delawski and F. T. Gelormini for technical assistance. Registry No. BCIP, 38404-93-2; hCG, 9002-61-3;Pv-Fc, 34801-99-5; APS reductase, 9027-75-2;quartz, 14808-60-7.
Synthesis, Characterization, and Reactivity of Oxomanganese( IV) Porphyrin Complexes John T. Groves* and Michael K. Stern Contribution from the Department of Chemistry, Princeton University, Princeton, New Jersey 08544. Received February 16, I988
Abstract: The preparation, isolation, and characterization of two types of oxomanganese(1V)porphyrin complexes are described. The reaction of chloro(5,10,15,20-tetramesitylporphyrinato)manganese(IIl)[Mn"'TMP(CI), 11 with 1.2 equiv of tetramethylammonium hydroxide (TMA(0H)) and 1.2 equiv of m-chloroperoxybenzoic acid (m-CPBA) in CH2CI2produced a second complex formulated as MnIVTMP(0) (2). The reaction of 1 in CH2C12containing excess tetra-n-butylammonium hydroxide (TBA(0H)) at +1.20 V generated a stable oxomanganese(1V)porphyrin complex, [MnNTMP(0)(OH)] (3). When the reaction stoichiometry was altered, mixtures of complexes 2 and 3 could be prepared. The aerobic reaction of 1 in CHCI, containing 6 N NaOH and a phase-transfer catalyst resulted in the formation of a similar complex, Mn"'TMP(O)(X) (Za). The addition of excess TBA(0H) to CH2CI2solutions of either 2 or 2a resulted in the quantitative formation of 3. The EPR spectra of 2, 2a, and 3 all displayed a strong broad resonance at g 4 and a weak unresolved signal at g 2 consistent with a high-spin (S = 3/2) assignment of the MnIVions. The MntV=O stretching frequency in 2 was identified at 754 cm-I by FT-IR spectroscopy. In the case of 3 the MntV=O stretching frequency was at 712 cm-'. The reaction of 2a with cis+ methylstyrene under anaerobic conditions produced a mixture of cis- and trans-epoxide in a ratio of 0.17. The reaction of 2 with cis-0-methylstyrene under aerobic conditions produced a different cis-epoxideltrans-epoxideratio and product distribution than those of the identical reaction run under anaerobic conditions. In the presence of H2I80,the stereoisomeric epoxides showed a significantly different I8O content. Further, l 8 0 was found to reside in the oxidation products when this reaction was carried out in the presence of Mechanisms for the epoxidation of olefins by 2 under anaerobic and aerobic conditions are discussed, which involve atom transfer from both oxomanganese(V) and oxomanganese(IV) species.
-
The oxygen activation and transfer reactions of cytochrome P-450 have attracted attention for over a decade. The remarkable reactivity of P-450 is believed to derive from an oxoiron(1V) porphyrin cation-radical species, which has been suggested as the ultimate oxidant in this enzymatic system.' Oxidized synthetic metalloporphyrin complexes have been extensively studied as simple active site models for monooxygenases and peroxidases and have provided a means to isolate and characterize reactive intermediates implicated in these biological systems.2 Indeed, structurally characterized oxometalloporphyrins of iron3 and ( I ) (a) Sligar, S . G.; Murray, R. I. Cyrochrome P-450: Structure, Mechanism, and Biochemistry; Oritz de Montellano, P. R., Ed.; Plenum: New York, 1986; pp 443-479. (b) Guengerich, F. P.; MacDonald, T. L. Acc. Chem. Res. 1984, 17, 9-16. (c) White, R. E.; Coon, M. J. Annu. Rev. Biochem. 1980,49,315-336.(d) Groves, J. T. Adu. Inorg. Eiochem. 1979,
119-145. (2)(a) Wolberg, J.; Monassen, J. J . Am. Chem. Soc. 1970,92,2982-2991. (b) Dunford, H. B.; Stillman, J. S. Coord. Chem. Reu. 1976,17,187-251. (c) McMurry, T. J.; Groves, J. T. Cytochrome P-450 Structure, Mechanism, ond Eiochemisrry;Oritz de Montellano, P. R., Ed.; Plenum: New York, 1986; pp 1-28.
0002-7863/88/ 15 IO-8628SO1.50/0
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chromium4 are known to be capable of oxidizing organic substrates. Further, dioxoruthenium( VI) and oxoruthenium( IV) porphyrin complexes have recently been identified as active species in the catalytic aerobic epoxidation of 01efins.~ (3)(a) Groves, J. T.; Haushaulter, R. C.; Nakamura, M.; Nemo, T. E.; Evans, B. J. J . Am. Chem. SOC.1981,103,2884-2886. (b) Penner-Hahn, J. E.; McMurry, T. J.; Renner, M.; Latos-Grazynsky, L.; Elbe, K. S . ; Davis, I. M.; Balch, A. L.; Groves, J. T.; Dawson, J. R.; Hodgson, K. 0. J . Biol. Chem. 1983,258, 12761-12764. (c) Boso, B.; Lang, L.; McMurry, T. J.; Groves, J. T. J . Chem. Phys. 1983,79,1122-1126. (d) Penner-Hahn, J. E.; Elbe, K. S.;McMurry, T. J.; Renner, M. R.; Balch, A. L.; Groves, J. T.; Dawson, J. H.; Hodgson, K. 0. J . Am. Chem. SOC.1986,108,7819-7825. ( e ) Chin, D. H.; Balch, A. L.; La Mar, G. N. J . Am. Chem. SOC.1980,102, 1446-1448. (0 Chin, D. H.; La Mar, G. N.; Balch, A. L. J. Am. Chem. SOC. 1980,102,4344-4350. (g) Balch, A. L.; La Mar, G. N.; Latos-Grazynski, L.; Renner, M. W.; Thanabal, V. J . Am. Chem. SOC.1985,107,3003-3007. (4)(a) Groves, J. T.; Kruper, W. J., Jr. J. Am. Chem. SOC.1979,101, 7613-7615. (b) Groves, J. T.; Haushaulter, R. C. J . Chem. Soc., Chem. Commun. 1981, 1163-1166. (c) Groves, J. T.; Kruper, W. J., Jr.; Haushaulter, R. C.; Butler, W. M. Inorg. Chem. 1982, 21, 1363-1368. (d) Penner-Hahn, J. E.; Benfatto, M.; Hedman, B.; Takahashi, T.; Sebastian, D.; Groves, J. T.; Hodgson, K. 0. Inorg. Chem. 1986,25,2255-2259.
0 1988 American Chemical Society
J . Am. Chem. Soc., Vol. 110, No. 26, 1988 8629
Oxomanganese(IV) Porphyrin Complexes Manganese porphyrin complexes have also received considerable scrutiny due to their unusually high reactivity toward olefin epoxidation and, particularly, the hydroxylation of unactivated C-H bonds6 A wide variety of catalytic systems employing manganese porphyrin complexes and oxidants such as iodosylbenzene,' NaOCl,* H202,9alkyl hydroperoxides,I0 Clod-, and IO4- l 1 have been developed. In addition, several aerobic processes for olefin epoxidation have been described.12 While it has been suggested that an MnV(0) species may be responsible for the observed reactivity in all of these systems, this complex has never been isolated or fully characterized. A variety of other monomeric and dimeric, high-valent manganese porphyrin complexes are known. Several of these complexes are capable of oxidizing organic substrate^.'^ A manganese(1V) bis(iodosy1benzene) adduct'3c and a dimeric (p-oxo)manganese(1V) bis(iodosy1benzene) species13chave been shown to functionalize both alkenes and alkanes. Further, two Mn(IV) complexes generated by NaOCI or NaOBr oxidation have been isolated and shown to be capable of transferring an oxygen atom to styrene and triphenylpho~phine.'~J%~ The stabilities of oxometalloporphyrin complexes of Cr( I n 4 Fe(IV),3w and R U ( I V ) suggest ~~ that a similar species should be accessible in the manganese system. Preliminary characterization of an oxomanganese(1V) porphyrin complex has been described by we is^.'^ W e have recently reported that the peroxy acid or electrochemical oxidation of chlor0(5,10,15,20-tetramesitylporphyrinato)manganese(III) [Mn"'TMP(Cl), 11 produced stable oxomanganese(1V) porphyrin complexe~.'~The M n " 4 moiety ( 5 ) (a) Groves, J. T.; Quinn, R. Imrg. Chem. 1984, 23, 3846-3853. (b) Groves, J. T.; Quinn, R. J . Am. Chem. SOC.1985, 107, 5790-5792. (c) Groves, J. T.; Ahn, K. H. Inorg. Chem. 1987, 26, 3831. (6) (a) Groves, J . T.; Watanabe, Y.;McMurry, T. J. J . Am. Chem. SOC. 1983, 105, 4489. (b) Groves, J. T.; Watanabe, Y . Inorg. Chem. 1986, 25, 4808. (c) Meunier, B. Bull. SOC.Chim. Fr. 1986, No. 4, 578-594, and references therein. (7) (a) Groves, J. T.; Kruper, W. J., Jr.; Haushaulter, R. C. J . Am. Chem. SOC.1980.102.6375-6377. (b) Hill. C. L.: Schardt. B. C. J. Am. Chem. Soc. 1980, 102, 6374-6375. (c) Hill, C: L.; Smegal, J.' A,; Henly, T. J. J . Org. Chem. 1983, 48, 3277-3281. (8) (a) Meunier, B.; Guilmet, E.; De Carvalho, M. E.; Poilblanc, R. J . Am. Chem. SOC.1984,106,6668-6676. (b) Meunier, B.; De Poorter, B. J . Chem. SOC.,Perkin Trans. 2 1385, 1735-1740. (c) Tabushi, 1.;Koga, N. Tetrahedron Lett. 1978,50,5017-5020. (d) Suslick, K. S.; Cook, B. R. J. Chem. Soc., Chem. Commun. 1987,200-202. ( e ) Collman, J. P.; Brauman, J. I.; Meunier, B.; Hayashi, T.; Kodadek, T.; Raybuck, S.A. J . Am. Chem. SOC.1985, 107, 2000-2005. (f) Collman, J. P.; Kcdadek, T.; Brauman, J. I . J . Am. Chem. SOC.1986, 108, 2588-2594. (9) Collman, J. P.; Brauman, J. I.; Meunier, B. Proc. Natl. Acad. Sei. U.S.A. 1984, 81, 3245-3248. (9) (a) Renaud, J.-P.; Battioni, P.; Bartoli, J. F.; Mansuy, D. J . Chem. Soc. Chem. Commun. 1985, 888-889. (b) Battioni, P.; Renaud, J.-P.; Bartoli, J. F.; Mansuy, D. J . Chem. SOC.,Chem. Commun. 1986, 341-343. (10) (a) Mansuy, D.; Battioni, P.; Renaud, J.-P. J . Chem. SOC.,Chem. Commun. 1984, 1255-1257. (b) Mansuy, D.; Bartoli, J.-F.; Momenteau, M. Tetrahedron Lett. 1982, 23, 2781-2784. (1 I ) (a) Takato, T.; Ando, W. Tetrahedron Lett. 1983,24,3631-3634. (b) Groves, J. T.; McMurry, T. J. Presented at the 187th National Meeting of the American Chemical Society, St. Louis, MO, April 1983. (c) Suslick, K. S.;Acholla, F. V.;Cook, B. R. J . Am. Chem. SOC.1987, 209, 2818-2819. (12) (a) Tabushi, I.; Koga, N. J . Am. Chem. SOC.1979, 101,6456-6458. (b) Tabushi, I.; Kcdera, M. J . Am. Chem. SOC.1986,108, 1101. (c) Tabushi, I.; Tazaki, A. J . Am. Chem. SOC.1981, 103, 7371-7373. (d) Tabushi, I.; Morimitsu, K. J . Am. Chem. SOC.1984, 106, 6871-6872. (e) Mansuy, D.; Fontecave, M.; Bartoli, J. F. J . Chem. SOC., Chem. Commun. 1983, 6, 253-254. ( f ) Creager, S. E.; Raybuck, S. A,; Murray, R. W. J . Am. Chem.
SOC.1986, 108, 4225-4227. (13) (a) Camenzind, M. J.; Hollander, F. J.; Hill, C. L. Inorg. Chem. 1982, 21, 4301-4308. (b) Camenzind, M. J.; Hollander, F. J.; Hill, C. L. Inorg. Chem. 1983,22,3776-3784. (c) Smegal, J. A,; Hill, C. L. J . Am. Chem. Soc. 1983, 105, 2920-2922. (d) Konishi, S.;Hoshimo, M.; Imamura, M. J . Phys. Chem. 1979, 101, 3681. (e) Smegal, J. A.; Schardt, B. C.; Hill, C. L. J. Am. Chem. SOC.1983, 105, 3510-3515. (f) Schardt, B. C.; Hollander, F. J.; Hill, C. L. J . Am. Chem. SOC.1982, 104, 3964-3972. (g) Smegal, J. A.; Hill, C. L. J . Am. Chem. Soc. 1983, 105, 3515-3521. (h) Camendzind, M. J.; Hollander, F. J.; Hill, C. L. Inorg. Chem. 1984, 23, 1984-1986. (i) Camendzind, M. J.; Hollander, F. J.; Hill, C. L. Inorg. Chem. 1983, 22, 3776-3784. Q) Bortolini, 0.;Meunier, B. J . Chem. SOC.,Chem. Commun. 1983, 1364. (k) Bortolni, 0.; Ricci, M.; Meunier, B.; Friant, P.; Ascone, I.; Goulon, J. Nouo. J . Chim. 1986, I O , 39-49. (I) Hill, C. L.; Hollander, F. J. J . Am. Chem. Soc. 1982, 104, 7318-7319. (m) Groves, J. T.; Takahashi, T. J . Am. Chem. SOC.1983,105, 2073-2074. (n) Rodgers, K. R.; Goff, H. M. J . Am. Chem. SOC.1987, 109,611-612. (14) Schappacher, M.; Weiss, R. Inorg. Chem. 1987, 26, 1190-1 192.
1.0
2
I
Ho
tfl2 4: a 0:
sa
3
a
3
400
500
600
700
'WAVELENGTH(nm)
Figure 1. Electronic absorption spectra of Mn"TMP(0) complexes. Porphyrin concentration was 7.32 X lod M. (A) (-) MnIVTMP(O) (2) generated by the reaction of 1 with 2.0 equiv of T M A ( 0 H ) and 1.2 equiv of m-CPBA in CH2C12 (A,, = 423, 472, 520 nm). (B) ( - - - ) M d V T M P ( 0 ) ( O H ) (3) generated by the addition of TBA(0H) to a CHzClz solution of 2.
was unambiguously identified by assignment of the MnIV=O stretching mode in these species by a combination of FT-IR and resonance Raman (RR) spectroscopy.16 We report here the preparation of several oxomanganese(IV) porphyrin complexes and their characterization by UV-vis, EPR, N M R and FT-IR spectroscopies. In addition, we describe the reactivity of these species with olefins under anaerobic and aerobic conditions and show that reactivity patterns are distinctly different for oxomanganese( IV) and oxomanganese(V) complexes. Results Preparation and Characterization of Oxomanganese(1V) Porphyrin Complexes. The oxidation of tetramesitylmanganese( 111) porphyrins with m-chloroperoxybenzoicacid under basic conditions has been shown to afford oxomanganese(1V) complexes. The reaction of chloro(5,10,15,20-tetramesitylporphyrinato)manganese(II1) [Mn"'TMP(Cl), 11 with (CH3),NOH and 1.2 equiv of m-chloroperoxybenzoic acid (m-CPBA) in CH,Cl, at 0 OC caused the immediate formation of a red species, 2, which was assigned the formulation Mn"TMP(0) (vide infra). It was possible to isolate 2 either by precipitation with hexane at -78 "C or by chromatography of the reaction mixture on basic alumina at -78 O C . The room-temperature bulk electrolysis of 1 with excess (n-Bu),NOH (TBA(0H)) in CH2CI2(0.1 M ( ~ - B u ) ~ N + C I O ~ - ) at +1.20 V resulted in the formation of a similar red species, 3, which we formulate as [Mn'VTMP(0)(OH)]-. It was possible to convert 2 into 3 by the reaction of 2 with TBA(0H). Samples of 2 purified by chromatography always contained some 3; how( 1 5 ) Groves, J. T.; Stern, M . K. J . Am. Chem. SOC.1987, 109, 3812. (16) Czernuszewicz, R. S.; Su, Y . 0.;Stern, M. K.; Macor, K. A.; Kim, D.; Groves, J. T.; Spiro, T. G. J . Am. Chem. SOC.1988, 110, 4158-4165.
Groves and Stern
8630 J . Am, Chem. SOC.,Vol. 110, No. 26, 1988
10
20
30
40
50
H (Kgouss'
Figure 3. EPR spectra of Mn'"TMP(0) complexes in CH2CI2at -150 OC. Spectrometer settings: scan range 10000 G , field set 5000 G , modulation amplitude 2.0 X lo', modulation frequency 100 kHz, microwave power 10 mW, microwave frequency 9.052 GHz. (A) Mn"TMP(0) (2). (B) Mn"TMP(0) (2) containing some 3. (C) Mn"TMP(O)(X) (2a). (D) Mn"TMP(O)(OH) (3).
340
380
420
460
500
540
580
610
WAVELENGTH(nm)
Figure 2. Key: (- - -) Visible spectrum of Mn"'TMP(0H) (la) resulting from the electrochemical reduction of Mn'"TMP(0) (2) at -0.1 V. (-) Visible spectrum of the reoxidation of la at +0.9 V generating 2. Porphyrin concentration was 1.6 X lo4 M.
ever, the reactions of 2 were not dependent on the nature of the isolation procedure. That 2 and 3 are at the oxidation state of Mn" and similar in structure was demonstrated by their visible and EPR spectra. The electronic absorption spectra of 2 and 3 (Figure 1) are characteristic of oxidized manganese porphyrin complexes. The visible spectrum of 2 had a broad Soret band at 422 nm. By contrast, the visible spectrum of 3 has a sharper red-shifted Soret at 425 nm. Thin-layer spectroelectrochemical analysis of 2 in CH2C12/0.1 M TBAP at 0 'C revealed that 2 could be isosbestically reduced at +0.1. V generating the visible spectrum of Mn"'TMP(0H) (la). Figure 2 shows that the reoxidation of this solution at +0.9 V quantitatively produced the spectrum of 2. This redox cycling could be repeated several times without significant porphyrin degradation. We conclude from this result that shuttling between 2 and l a under these conditions is a chemically reversible process. The EPR spectra of 2 and 3 (Figure 3) have the characteristic g - 4 , g - 2 signal of high-spin, d3, monomeric Mn(IV) complexes. However, the relative intensity and position of these signals varied slightly upon going from the five-coordinate species 2 to the six-coordinate species 3. It was also possible to prepare the MnIVTMP(0) complex by the aerobic reaction of 1 in CHC13 with TBA(0H). This reaction resulted in the disappearance of the visible absorbances due to 1 and the formation of a red species, MnwTMP(0)(X) (2a) with absorption bands similar to 2 and 3. Either CHIC], or benzene could be used as solvent in the presence of several hundred equivalents of CHC1, or CHBr,. Furthermore, when TBA(0H) was replaced by triethylbenzylammonium chloride (TEBA) and 6 N NaOH, an excellent phase-transfer system for carbene form a t i ~ n , the ' ~ generation of 2a proceeded with an approximate 5-fold increase in rate. It was possible to do preparative scale ( I 7) Dehmlow, E. V.; Dehmlow, S . S. Phase Transfer Catalysis; Verlag Chemie: Weinheim, FRG, 1980.
2a
L
900
I
800
I
700 CM-'
1
600
k00
Figure 4. Infrared spectra (KBr pellet) of MnNTMP(0) complexes: (A) Mn"'TMP(C1) (1); (B) Mn"TMP(0) (2) prepared by the reaction of 1 with 1.2 equiv of T M A ( 0 H ) and 1.2 equiv of m-CPBA in CH2C12and precipitated from hexane; (C) Mn"'TMP(0) (2) generated by the reaction of 1 with 2.0 equiv of T M A ( 0 H ) and 1.2 equiv of m-CPBA in CHIC], and isolated by chromatography; (D) MnIVTMP(O)(OH) (3) prepared by electrooxidation of 1 at +1.20 V in CH2CI2containing excess TBA(0H); (E) Mn"TMP(O)(X) (2a) prepared by the aerobic reaction of 1 in CH2C12containing CHCI, and 6 N NaOH.
reactions under these conditions and to isolate 2a by low-temperature alumina chromatography. If either CHCl,, NaOH, or O2were excluded, 2a was not formed. The EPR spectrum of 2a was nearly identical with that of 2 isolated by chromatography (Figure 3). The conversion of 2a to 3 could also be achieved by the addition of TBA(0H). Accordingly, we conclude that 2a is a mixture of 2 and 3. IR, NMR, and Mass Spectra. The KBr pellet IR spectra of 1, 2, 2a, and 3 are shown in Figure 4. On the basis of the visible
J . Am. Chem. SOC.,Vol. 110, No. 26, 1988 8631
Oxomanganese(IV) Porphyrin Complexes
Table I. Anaerobic Reaction of Oxomanganese(1V) and Oxomanganese(V) Porphyrin Complexes with @-Methylstyrene vields. %
wo v:
oxidant (temp, "C) 2b (25) 2 4 ' (25) 3' (25) 3".b (25) 2a (25) 2a (25) 2a (25) 4 (-78) 4" (-78) 2 (-78) 4 (-78) 4" (-78) 2 (-78)
P-methylstyrene ciscisciscisciscistranscisciscis-
transtranstrans-
cis/trans 0.57 0.50 0.06 0.05 0.12 0.13
/
/
16 8 4 4 4 4
28 16 62 70 32 30 34 12 9 8 5 22
