Steric control of electron transfer. Changeover from outer-sphere to inner-sphere mechanisms in arene/quinone redox pairs

Journal of the American Chemical Society

Volumn 121, Issue 4, 1999, Pages 617-626

  Hubig, Stephan M ^a   Rathore, Rajendra ^a   Kochi, Jay K ^a  

^a University of Houston   (United States)

Author keywords

[No Author keywords available]

Indexed keywords

1,4 BENZOQUINONE; POLYCYCLIC AROMATIC HYDROCARBON;

ARTICLE; COMPLEX FORMATION; ELECTRON TRANSPORT; EQUILIBRIUM CONSTANT; OXIDATION REDUCTION REACTION; PHOTOACTIVATION; REACTION TIME; STEREOCHEMISTRY; STEREOSPECIFICITY; STRUCTURE ACTIVITY RELATION; STRUCTURE ANALYSIS; TEMPERATURE DEPENDENCE;

EID: 0033518578     PISSN: 00027863     EISSN: None     Source Type: Journal    
DOI: 10.1021/ja9831002     Document Type: Article

References (124)

1. Eyring, H.; Polanyi, M. Z. Phys. Chem. 1931, B12, 279.
2. (b) Glasstone, S.; Laidler, K. J.; Eyring, H. The Theory of Rate Processes; McGraw-Hill: New York, 1941.
3. -1 have been determined for electron-transfer processes within electron donor/acceptor complexes. See: (a) Wynne, K.; Galli, C.; Hochstrasser, R. M. J. Chem. Phys. 1994, 100, 4797.
4. (b) Asahi, T.; Mataga, N. J. Phys. Chem. 1989, 93, 6575. See also: Hannappel, T.; Burfeindt, B.; Storck, W.; Willig, F. J. Phys. Chem. 1997, B101, 6799.
5. (b) Asahi, T.; Mataga, N. J. Phys. Chem. 1989, 93, 6575. See also: Hannappel, T.; Burfeindt, B.; Storck, W.; Willig, F. J. Phys. Chem. 1997, B101, 6799.
6. Traditionally, electron-transfer reactions are classified as either "inner-sphere" (bonded) or "outer-sphere" (nonbonded) processes. See: (a) Taube, H. Electron-Transfer Reactions of Complex Ions in Solution; Academic Press: New York, 1970.
7. (b) Cannon, R. D. Electron-Transfer Reactions; Butterworth: London, 1980.
8. (c) Zipse, H. Angew. Chem., Int. Ed. Engl. 1997, 36, 1697.
9. (d) Eberson, L. New J. Chem. 1992, 16, 151.
10. (e) Tributsch, H.; Pohlmann, L. Science 1998, 279, 1891.
11. See: (a) Polanyi, J. C.; Zewail, A. H. Acc. Chem. Res. 1995, 28, 119.
12. (b) Zhong, D.; Zewail, A. H. J. Phys. Chem. 1998, A102, 4031.
13. Sastry, G. N.; Shaik, S. J. Am. Chem. Soc. 1998, 120, 2131.
14. (b) Eberson, L.; Shaik, S. S. J. Am. Chem. Soc. 1990, 112, 4484.
15. (c) Bertran, J.; Gallardo, I.; Moreno, M.; Savéant, J.-M. J. Am. Chem. Soc. 1996, 118, 5737.
16. (d) Su, J. T.; Zewail, A. H. J. Phys. Chem. 1998, A102, 4082.
17. +) + ⋯
18. Mulliken, R. S. J. Am. Chem. Soc. 1950, 72, 600.
19. (b) Mulliken, R. S. J. Am. Chem. Soc. 1952, 74, 811.
20. (c) Mulliken, R. S.; Person, W. M. Molecular Complexes; Wiley: New York, 1969.
21. 2, see: (a) Ketelaar, J. A. A. J. Phys. Radium 1954, 15, 197.
22. (b) Tamres, M.; Brandon, M. J. Am. Chem. Soc. 1960, 82, 2134.
23. See also: (c) Briegleb, G. Elektronen-Acceptor-Komplexe; Springer: Berlin, 1961.
24. Rathore, R.; Hubig, S. M.; Kochi, J. K. J. Am. Chem. Soc. 1997, 119, 11468.
25. Hubig, S. M.; Kochi, J. K. J. Am. Chem. Soc. In press.
26. Compare: Rehm, D.; Weller, A. Isr. J. Chem. 1970, 8, 259.
27. Rathore, R.; Lindeman, S. V.; Kochi, J. K. J. Am. Chem. Soc. 1997, 119, 9393.
28. (b) For the effects of steric hindrance on exciplex formation, see: Jacques, P.; Allonas, X.; Suppan, P.; Von Raumer, M. J. Photochem. Photobiol. 1996, A 101, 183.
29. The precursor or encounter complex (prior to electron transfer) and the ET transition state are assumed to be structurally similar and exhibit more or less comparable donor/acceptor interactions. See: (a) Sutin, N. Acc. Chem. Res. 1968, 1, 225.
30. Compare also: (b) Marcus, R. A. J. Chem. Phys. 1956, 24, 966.
31. Marcus, R. A. Angew. Chem., Int. Ed. Engl. 1993, 32, 1111 and references therein.
32. T) of the quinones, see: (a) Shcheglova, N. A.; Shigorin, D. N.; Yakobson, G. G. Y.; Tushishvili, L. Sh. Russ. Phys. Chem. 1969, 43, 1112.
33. (b) Trommsdorff, H. P.; Sahy, P.; Kahane-Paillous Spectrochim. Acta 1968, 24A, 785.
34. (c) Herre, W.; Weis, P. Spectrochim. Acta 1973, 29A, 203.
35. (d) Koboyama, A. Bull. Chem. Soc. Jpn. 1962, 35, 295.
36. For the reduction potentials of the quinones (in the ground state), see: (e) Mann, C. K.; Barnes, K. K. Electrochemical Reactions in Non-Aqueous Systems; Dekker: New York, 1970.
37. (f) Peover, J. E. J. Chem. Soc. 1962, 4540.
38. (a) Howell, J. O.; Goncalvez, J. M.; Amatore, C.; Klasinc, L.; Wightman, R. M.; Kochi, J. K. J. Am. Chem. Soc. 1984, 106, 3968.
39. 12 In addition, a few "partially" hindered donors are included in this study to demonstrate the effects of the (ring) position of bulky substituents on the overall steric encumbrance of the arene.
40. Furthermore, the use of uncharged redox partners allows the electron transfer to be studied in aprotic polar as well as nonpolar solvents (to avoid the rather unique ionic solvation by water). Note also that the charge-delocalization and charge-transfer ability is optimized in such multiatom (expanded) redox centers of the donor/acceptor pair.
41. 0 being the donor-acceptor distance at van der Waals contact.
42. (b) See: Endicott, J. F.; Kumar, K.; Ramasami, T.; Rotzinger, F. P. Prog. Inorg. Chem. 1983, 30, 141 and references therein.
43. 19
44. -1).
45. Gould, I. R.; Young, R. H.; Moody, R. E.; Farid, S. J. Phys. Chem. 1991, 95, 2068.
46. (b) Gould, I. R.; Young, R. H.; Mueller, L. J.; Farid, S. J. Am. Chem. Soc. 1994, 116, 8176.
47. (c) Tachiya, M.; Murata, S. J. Am. Chem. Soc. 1994, 116, 2434.
48. Miller, J. R.; Calcaterra, L. T.; Closs, G. L. J. Am. Chem. Soc. 1984, 106, 3047.
49. (b) Closs, G. L.; Calcaterra, L. T.; Green, N. J.; Penfield, K. W.; Miller, J. R. J. Phys. Chem. 1986, 90, 3673.
50. (c) Wasilewski, M. R.; Niemczyk, M. P.; Svec, W. A.; Pewitt, E. B. J. Am. Chem. Soc. 1985, 107, 1080.
51. (d) Paddon-Row, M. N. Acc. Chem. Res. 1994, 27, 18.
52. Gould, I. R.; Noukakis, D.; Gomez-Jahn, L.; Goodman, J. L.; Farid, S. J. Am. Chem. Soc. 1993, 115, 4405.
53. Gould, I. R.; Young, R. H.; Mueller, L. J.; Albrecht, A. C.; Farid, S. J. Am. Chem. Soc. 1994, 116, 8188.
54. Benniston, A. C.; Harriman, A.; Philp, D.; Stoddart, J. F. J. Am. Chem. Soc. 1993, 115, 5298.
55. Haim, A. Prog. Inorg. Chem. 1983, 30, 273.
56. Creutz, C. Prog. Inorg. Chem. 1983, 30, 1.
57. (b) Creutz, C.; Taube, H. J. Am. Chem. Soc. 1969, 91, 3988.
58. (c) Goldsby, K. A.; Meyer, T. J. Inorg. Chem. 1984, 23, 3002.
59. Burewicz, A.; Haim, A. Inorg. Chem. 1988, 27, 1611.
60. 23-25
61. Astruc, D. Electron Transfer and Radical Processes in Transition-Metal Chemistry; VCH: New York, 1995; p 30.
62. 3a that is largely based on ionic (inorganic) coordination complexes by including uncharged (organic) redox systems with measurable donor/ acceptor coupling. We believe it is highly desirable to retain the classical inner-sphere/outer-sphere distinction in this modified form (to avoid inventing new terms) so that a universal and common terminology can be applied to describe electron-transfer mechanisms in all branches of inorganic chemistry, organic chemistry, and biochemistry.
63. 17b,41b
64. Note also that an inner-sphere/outer-sphere distinction based on orbital overlap allows for a continuum of intermediate cases to exist between the two idealized models that depend on the degree of electronic coupling. Moreover, the simultaneous occurrence of both mechanisms is readily accounted for in medium-strong interactions. See: (a) Taube, H.; Myers, H. J. Am. Chem. Soc. 1954, 76, 2103.
65. (b) Melvin, W. S.; Haim, A. Inorg. Chem. 1977, 16, 2016.
66. (c) Connocchioli, T. J.; Hamilton, E. J.; Sutin, N. J. Am. Chem. Soc. 1965, 87, 926.
67. For the suggestion of a continuum, see: (d) Fukuzumi, S.; Wong, C. L.; Kochi, J. K. J. Am. Chem. Soc. 1980, 102, 2928.
68. (e) Rosseinsky, D. R. Chem. Rev. 1972, 72, 215.
69. (f) Eberson, L. Adv. Phys. Org. Chem. 1982, 18, 79.
70. Juillard, M.; Chanon, M. Chem. Rev. 1983, 83, 425.
71. 2 in Table 1 represents the upper limit of the second-order rate constant for electron transfer.
72. 33b unambiguously show that the hydrogen transfer can occur via (rate-determining) electron transfer followed by fast proton transfer.
73. (b) Bockman, T. M.; Hubig, S. M.; Kochi, J. K. J. Am. Chem. Soc. 1998, 120, 2826.
74. (c) As a measure for the solvent polarity, the dielectric constants were taken. See: Murov, S. L.; Carmichael, I.; Hug, G. L. Handbook of Photochemistry, 2nd ed.; Dekker: New York, 1993.
75. Moore, J. W.; Pearson, R. G. Kinetics and Mechanisms, 3rd ed.; Wiley: New York, 1981; p 239f.
76. -1. See: Eigen, M. Z. Phys. Chem. N. F. (Leipzig) 1954, 1, 176.
77. 11 Various theoretical explanations of the "non-Marcus" behavior (i.e., the lack of the "Marcus-inverted" region) have been reported:
78. (b) Kakitani, T.; Yoshimori, A.; Mataga, N. J. Phys. Chem. 1992, 96, 5385.
79. (c) Kikuchi, K.; Takahashi, Y.; Katagairi, T.; Niwa, T.; Hoshi, M.; Miyashi, T. Chem. Phys. Lett. 1991, 180, 403.
80. (d) Gould, I. R.; Young, R. H.; Mueller, L. J.; Farid, S. J. Am. Chem. Soc. 1994, 116, 8176.
81. ET values of Table 1 were shifted by α = -0.4 eV. For a theoretical explanation of the shift parameter α, see: Tamura, S.-I.; Kikuchi, K.; Kokubun, H.; Usui, Y. Z. Phys. Chem. N. F. (Wiesbaden) 1978, 111, 7.
82. -1, as extracted from the Marcus treatment of the data in Figure 1.
83. Bunnett, J. F. In Investigation of Rates and Mechanisms of Reactions; Part 1; Bernasconi, C. F., Ed.; Wiley: New York, 1986; p 286f.
84. For a mechanistic description of the limiting kinetics behavior, see: Espenson, J. D. Chemical Kinetics and Reaction Mechanisms, 2nd ed.; McGraw-Hill: New York, 1995; p 89f.
85. (b) For the decay kinetics of photoexcited quinones, see; Kobashi, H.; Okada, T.; Mataga, N. Bull. Chem. Soc. Jpn. 1986, 59, 1975.
86. 9
87. -1). See ref 9.
88. 9,12a As a consequence, inner-sphere ET is readily recognized by its unusually fast rates, significant deviations from the Marcus-predicted driving-force dependence, and pronounced sensitivity to steric hindrance. For earlier studies, see: (a) Fukuzumi, S.; Wong, C. L.; Kochi, J. K. J. Am. Chem. Soc. 1980, 102, 2928.
89. (b) Fukuzumi, S.; Kochi, J. K. Bull. Chem. Soc. Jpn. 1983, 56, 969.
90. (c) Kochi, J. K. Angew. Chem., Int. Ed. Engl. 1988, 27, 1227.
91. For inner-sphere descriptions of ion-pair states, see: (a) Hubig, S. M.; Bockman, T. M.; Kochi, J. K. J. Am. Chem. Soc. 1996, 118, 3842.
92. (b) Bockman, T. M.; Karpinski, Z. J.; Sankararaman, S.; Kochi, J. K. J. Am. Chem. Soc. 1992, 114, 1970.
93. (c) Hörmann, A.; Jarzeba, W.; Barbara, P. F. J. Phys. Chem. 1995, 99, 2006.
94. Reynolds, W. L.; Lumry, R. W. Mechanisms of Electron Transfer; Ronald Press: New York, 1966; p 12.
95. 3•): Del Giacco, T.; Baciocchi, E.; Steenken, S. J. Phys. Chem. 1993, 97, 5451.
96. (b) Reduction of nitroarenes by oxygen atom transfer to Rucarbonyl complexes: Skoog, S. J.; Gladfelter, W. L. J. Am. Chem. Soc. 1997, 119, 11049.
97. (c) Reduction of methyl iodide by HI: Holm, T.; Crossland, I. Acta Chem. Scand. 1996, 50, 90.
98. Harding, T. T.; Wallwork, S. C. Acta Crystallogr. 1955, 8, 757.
99. Based on molecular-mechanics calculations in ref 12a.
100. -1, which corresponds to a lifetime of 50 ps. See also: Marcus, R. A. in ref 6a.
101. For steric effects on other photoinduced electron transfers, see: (a) Jones, G., II; Chatterjee, S. J. Phys. Chem. 1988, 92, 6862.
102. (b) Gassman, P. G.; DeSilva, S. A. J. Am. Chem. Soc. 1991, 113, 9870.
103. (c) Gould, I. R.; Farid, S. J. Phys. Chem. 1993, 97, 13067.
104. Baggott, J. E.; Pilling, M. J. J. Chem. Soc., Faraday Trans. 1 1983, 79, 221.
105. (b) See also: Baggott, J. E. In Photoinduced Electron Transfer, Fox, M. A., Chanon, M., Eds.; Elsevier: New York, 1988; Part B, p 385f.
106. Asahi, T.; Ohkohchi, M.; Mataga, N. J. Phys. Chem. 1993, 97, 13132.
107. Asahi, T.; Ohkohchi, M.; Matsusaka, T.; Mataga, N.; Zhang, R. P.; Osuka, A.; Maruyama, K. J. Am. Chem. Soc. 1993, 115, 5665.
108. Gordon, J. E. The Organic Chemistry of Electrolyte Solutions; Wiley: New York, 1975; p 99f.
109. (b) Masnovi, J. M.; Kochi, J. K. J. Am. Chem. Soc. 1985, 107, 7880.
110. (c) Yabe, T.; Kochi, J. K. J. Am. Chem. Soc. 1992, 114, 4491.
111. However, the electron-transfer rate constants of the pyrene/cyanoarene systems were found to be slower than those predicted by Marcus theory for "outer-sphere" electron transfer. As such, reaction pathways other than electron transfer were invoked to account for the low rate constants of fluorescence quenching of pyrene and naphthalene by cyanoarenes. In our study, the ion-radical yields of unity for most donor/acceptor couples (see Table 1) rule out such alternative pathways.
112. AB results in adiabatic electron transfer with unit probability. See: Marcus, R. A.; Sutin, N. Biochim. Biophys. Acta 1985, 811, 265.
113. In these electron transfers, the weak electronic coupling between the sterically encumbered redox partners leads (in its extreme) to a nonadiabatic (diabatic) electron transfer that (in the isergonic and endergonic driving-force region) results in very slow rates. For examples of nonadiabatic electron transfers due to steric hindrance, see: (a) Rau, H.; Frank, R.; Greiner, G. J. Phys. Chem. 1986, 90, 2476.
114. (b) Sandrini, D.; Maestri, M.; Belser, P.; Von Zelewski, A.; Balzani, V. J. Phys. Chem. 1985, 89, 3675.
115. (c) Koval, C. A.; Pravata, R. L. A.; Reidsema, C. M. Inorg. Chem. 1984, 23, 545.
116. (d) Koval, C. A.; Ketterer, M. E. J. Electroanal. Chem. 1984, 175, 263.
117. (e) Kitamura, N.; Rajagopal, S.; Tazuke, S. J. Phys. Chem. 1987, 91, 3767.
118. 36b] Accordingly, the observation of steric effects on the rate constants for bimolecular electron transfers in the highly exergonic driving-force region (and possibly the observation of the Marcus-inverted region) is only expected at driving forces and donor/acceptor distances at which the electron transfer is the rate-limiting step following the diffusional formation of the encounter complex. Other explanations for the lack of an inverted driving-force dependence of bimolecular electron-transfer rate constants in the exergonic region are cited in ref 36. The possibility of observing the inverted region in extremely hindered organic donors/acceptors is under investigation.
119. The electron transfer does not effect any net bond formation or bond cleavage in either reactant. Moreover, back electron transfer in acetonitrile solution completely restores the starting donor/acceptor pairs.
120. Bruson, H. A.; Kroeger, J. W. J. Am. Chem. Soc. 1940, 62, 36.
121. Perrin, D. D.; Armarego, W. L. F. Purification of Laboratory Chemicals, 3rd ed.; Pergamon: Oxford, 1988.
122. Bockman, T. M.; Karpinski, Z. J.; Sankararaman, S.; Kochi, J. K. J. Am. Chem. Soc. 1992, 114, 1970.
123. Hurley, J. K.; Sinai, N.; Linschitz, H. Photochem. Photobiol. 1983, 38, 9.
124. André, J. J.; Weill, G. Mol. Phys. 1968, 15, 97.