Bridge-mediated hopping or superexchange electron-transfer processes in bis(triarylamine) systems
Source abstract
Abstract
Hopping and superexchange are generally considered to be alternative electron-transfer mechanisms in molecular systems. In this work we used mixed-valence radical cations as model systems for the investigation of electron-transfer pathways. We show that substituents attached to a conjugated bridge connecting two triarylamine redox centres have a marked influence on the near-infrared absorption spectra of the corresponding cations. Spectral analysis, followed by evaluation of the electron-transfer parameters using the Generalized Mulliken-Hush theory and simulation of the potential energy surfaces, indicate that hopping and superexchange are not alternatives, but are both present in the radical cation with a dimethoxybenzene bridge. We found that the type of electron-transfer mechanism depends on the bridge-reorganization energy as well as on the bridge-state energy. Because superexchange and hopping follow different distance laws, our findings have implications for the design of new molecular and polymeric electron-transfer materials.
Source: europepmc · Quality: candidate unverified · Source record ↗
Research context
OpenAlex topics: Photochemistry and Electron Transfer Studies · Luminescence and Fluorescent Materials · Organic Light-Emitting Diodes Research
SciVX discovery tags are terminology-based. OpenAlex topics are source-provided classifications.
References (36)
Show source-provided references
1. Segal, D., Nitzan, A., Davis, W.B., Wasielewski, M.R. & Ratner, M.A. Electron transfer rates in bridged molecular systems 2. A steady-state analysis of coherent tunneling and thermal transitions. J. Phys. Chem. B 104, 3817–3829 (2000).10.1021/jp993260f ↗
2. Paddon-Row, M.N. in Electron Transfer in Chemistry (ed. Balzani, V.) 179–271 (Wiley-VCH, Weinheim, 2001).
3. De Cola, L. & Belser, P. in Electron Transfer in Chemistry (ed. Balzani, V.) 97–136 (Wiley-VCH, Weinheim, 2001).10.1002/9783527618248.ch66 ↗
4. Kilså, K., Kajanus, J., Macpherson, A.N., Mårtensson, J. & Albinsson, B. Bridge-dependent electron transfer in porphyrin-based donor-bridge-acceptor systems. J. Am. Chem. Soc. 123, 3069–3080 (2001).10.1021/ja003820k ↗
5. Launay, J.-P. Long-distance intervalence electron transfer. Chem. Soc. Rev. 30, 386–397 (2001).10.1039/b101377g ↗
6. Newton, M.D. Quantum chemical probes of electron-transfer kinetics: The nature of donor-acceptor interactions. Chem. Rev. 91, 767–792 (1991).10.1021/cr00005a007 ↗
7. Nelsen, S.F., Ismagilov, R.F. & Powell, D.R. Effects of bridge redox state levels on the electron transfer and optical properties of intervalence compounds with hydrazine charge-bearing units. J. Am. Chem. Soc. 120, 1924–1925 (1998).10.1021/ja972760o ↗
8. Davis, W.B., Svec, W.A., Ratner, M.A. & Wasielewski, M.R. Molecular-wire behaviour in p-phenylenevinylene oligomers. Nature 396, 60–63 (1998).10.1038/23912 ↗
9. Weiss, D.S., Cowdery, J.R. & Young, R.H. in Electron Transfer in Chemistry (ed. Balzani, V.) 379–471 (Wiley-VCH, Weinheim, 2001).10.1002/9783527618248.ch73 ↗
10. Bässler, H. in Semiconducting Polymers (eds. Hadziioannou, G. & van Hutten, P.F.) 365–410 (Wiley-VCH, Weinheim, 2000).
11. Herz, T., Gedeck, P. & Clark, T. Fast long-range adiabatic electron transfer in a model polyglycine α-helix. J. Am. Chem. Soc. 121, 1379–1380 (1999).10.1021/ja9836500 ↗
12. Tollin, G. in Electron Transfer in Chemistry (ed. Balzani, V.) 202–231 (Wiley-VCH, Weinheim, 2001).10.1002/9783527618248.ch51 ↗
13. Lewis, F.D. in Electron Transfer in Chemistry (ed. Balzani, V.) 105–175 (Wiley-VCH, Weinheim, 2001).10.1002/9783527618248.ch37 ↗
14. Giese, B. Long-distance charge transport in DNA: The hopping mechanism. Acc. Chem. Res. 33, 631–636 (2000).10.1021/ar990040b ↗
15. Lambert, C. & Nöll, G. One- and two-dimensional electron transfer processes in triarylamines with multiple redox centres. Angew. Chem. Int. Ed. 37, 2107–2110 (1998).10.1002/(SICI)1521-3773(19980817)37:15<2107::AID-ANIE2107>3.0.CO;2-H ↗
16. Lambert, C. & Nöll, G. The class II/III transition in triarylamine redox systems. J. Am. Chem. Soc. 121, 8434–8442 (1999).10.1021/ja991264s ↗
17. Nelsen, S.F., Ismagilov, R.F. & Trieber, D.A. Adiabatic electron transfer: comparison of modified theory with experiment. Science 278, 846–849 (1997).10.1126/science.278.5339.846 ↗
18. Schmidt, W. & Steckhan, E. Organic electron transport systems. I. Electrochemical and spectroscopic study of bromo-substituted triarylamine redox systems. Chem. Ber. 113, 577–585 (1980).10.1002/cber.19801130215 ↗
19. Dapperheld, S., Steckhan, E., Brinkhaus, K.-H.G. & Esch, T. Substituted triarylamine cation-radical redox systems - synthesis, electrochemical and spectroscopic properties, Hammet behavior, and suitability as redox catalysts. Chem. Ber. 124, 2557–2567 (1991).10.1002/cber.19911241127 ↗
20. Neugebauer, F.A., Bamberger, S. & Groh, W.R. Mono-, di-, and triarylamine radical cations. Chem. Ber. 108, 2406–2415 (1975).10.1002/cber.19751080728 ↗
21. Le Stang, S., Paul, F. & Lapinte, C. Molecular wires: synthesis and properties of the new mixed-valence complex [Cp*(dppe)Fe-CC-X-CC-Fe(dppe)Cp*][PF6] (X = 2,5 -C4H2S) and comparison of its properties with those of the related all-carbon-bridged complex (X = -C4-). Organometallics 19, 1035–1043 (2000).10.1021/om9908231 ↗
22. Lindeman, S.V., Rosokha, S.V., Sun, D. & Kochi, J.K. X-ray structure analysis and the intervalent electron transfer in organic mixed-valence crystals with bridged aromatic cation radicals. J. Am. Chem. Soc. 124, 843–855 (2002).10.1021/ja011579j ↗
23. Hush, N.S. Distance dependence of electron transfer rates. Coord. Chem. Rev. 64, 135–157 (1985).10.1016/0010-8545(85)80047-3 ↗
24. Root, L.J. & Ondrechen, M.J. Adiabatic potentials for a bridged three-site electron-transfer system. Chem. Phys. Lett. 93, 421–424 (1982).10.1016/0009-2614(82)83213-2 ↗
25. Ko, J. & Ondrechen, M.J. Line shape of the intervalence transfer band in bridged mixed-valence dimers: The delocalized case. J. Am. Chem. Soc. 107, 6161–6167 (1985).10.1021/ja00308a003 ↗
26. Borshch, S.A., Kotov, I.N. & Bersuker, I.B. Electron delocalization in trinuclear mixed-valence clusters. Chem. Phys. Lett. 89, 381–384 (1982).10.1016/0009-2614(82)80005-5 ↗
27. Brunschwig, B.S., Creutz, C. & Sutin, N. Optical transitions of symmetrical mixed-valence systems in the class II–III transition regime. Chem. Soc. Rev. 31, 168–184 (2002).10.1039/b008034i ↗
28. Newton, M.D. Control of electron transfer kinetics: Models for medium reorganization and donor-acceptor coupling. Adv. Chem. Phys. 106, 303–375 (1999).
29. Creutz, C., Newton, M.D. & Sutin, N. Metal-ligand and metal-metal coupling elements. J. Photochem. Photobiol. A 82, 47–59 (1994).10.1016/1010-6030(94)02013-2 ↗
30. Cave, R.J. & Newton, M.D. Generalization of the Mulliken-Hush treatment for the calculation of electron transfer matrix elements. Chem. Phys. Lett. 249, 15–19 (1996).10.1016/0009-2614(95)01310-5 ↗
31. Fernández, E., Blancafort, L., Olivucci, M. & Robb, M.A. Intramolecular electron transfer: Independent (ground state) adiabatic (chemical) and nonadiabatic reaction pathways in bis(hydrazine) radical cations. J. Am. Chem. Soc. 122, 7528–7533 (2000).10.1021/ja000013c ↗
32. Nelsen, S.F., Ismagilov, R.F. & Powell, D.R. Charge-localized p-phenylenedihydrazine radical cations: ESR and optical studies of intramolecular electron transfer rates. J. Am. Chem. Soc. 119, 10213–10222 (1997).10.1021/ja9720321 ↗
33. Nelsen, S.F., Trieber, D.A., Ismagilov, R.F. & Teki, Y. Solvent effects on charge transfer bands of nitrogen-centered intervalence compounds. J. Am. Chem. Soc. 123, 5684–5694 (2001).10.1021/ja003436n ↗
34. Pfennig, B.W., Fritchman, V.A. & Hayman, K.A. Synthesis, characterization, and photophysical properties of a series of supramolecular mixed-valence compounds. Inorg. Chem. 40, 255–263 (2001).10.1021/ic000706u ↗
35. Rathore, R., Lindeman, S.V., Kumar, A.S. & Kochi, J.K. Disproportionation and structural changes of tetraarylethylene donors upon successive oxidation to cation radicals and to dications. J. Am. Chem. Soc. 120, 6931–6939 (1998).10.1021/ja981095w ↗
36. Nelsen, S.F. & Newton, M.D. Estimation of electron transfer distances from AM1 calculations. J. Phys. Chem. A 104, 10023–10031 (2000).10.1021/jp002211w ↗