The class II/III transition electron transfer on an infrared vibrational time scale for N,N′-diphenyl-1,4-phenylenediamine structures

被引:34
作者
Nishiumi, T [1 ]
Nomura, Y [1 ]
Chimoto, Y [1 ]
Higuchi, M [1 ]
Yamamoto, K [1 ]
机构
[1] Keio Univ, Dept Chem, Fac Sci & Technol, Yokohama, Kanagawa, Japan
关键词
D O I
10.1021/jp0492265
中图分类号
O64 [物理化学(理论化学)、化学物理学];
学科分类号
070304 ; 081704 ;
摘要
Intramolecular electron transfer (ET) within the class II/III transition for the mixed-valence state of N,N'-diphenyl-1,4-phenylenediamine (PDA) derivatives which were substituted in the center or the outer phenyl ring and N,N'-diphenylbenzidine (BZ) was examined. Each compound showed two reversible redox couples. The splitting of the redox waves, DeltaE, is related to the interaction intensity between redox sites. The introduction of a substitutent into the central phenylene ring of the PDAs resulted in a decrease in DeltaE. A similar result was noted for the expansion of the distance between the redox centers such as in BZ. In opposition, the DeltaE of N,N'-bis(2,6-dimethylphenyl)-1,4-phenylenediamine (2,6-DMPDA) as a compound with substituents introduced into the outer phenyl rings was spread. The mixed-valence state of these compounds also exhibited an intervalence charge transfer (IV-CT) band in the near-IR region which provided the determination of the Marcus reorganization energy (lambda), the electron coupling (V), the thermal ET barrier (DeltaG*), and the electron-transfer rate (k(th)) using the Marcus-Hush theory. We first confirmed the electron-transfer rate of PDA derivatives in the class II/III transition state by two methods. The v(N-H) stretching vibrational spectra of the mixed-valence states were analyzed by a Bloch-type equation analysis using variable-temperature IR spectra measurements which were to be in good agreement with the those obtained from the Marcus-Hush theory. On the basis of this approach, the electron-transfer rate of PDA was determined to be 8.2 x 10(11) s(-1) at 298 K, yielding DeltaG(double dagger) = 420 cm(-1) (the activation free energy from the Eyring plot) for the underlying process.
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页码:7992 / 8000
页数:9
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