10189-13-6Relevant articles and documents
The class II/III transition electron transfer on an infrared vibrational time scale for N,Na?2-diphenyl- 1,4-phenylenediamine structures
Nishiumi, Toyohiko,Nomura, Yasuhiro,Chimoto, Yuya,Higuchi, Masayoshi,Yamamoto, Kimihisa
, p. 7992 - 8000 (2004)
Intramolecular electron transfer (ET) within the class II/III transition for the mixed-valence state of N,Na?2-diphenyl-1,4-phenylenediamine (PDA) derivatives which were substituted in the center or the outer phenyl ring and N,Na?2-diphenylbenzidine (BZ) was examined. Each compound showed two reversible redox couples. The splitting of the redox waves, ??E, 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 ??E. A similar result was noted for the expansion of the distance between the redox centers such as in BZ. In opposition, the ??E of N,Na?2-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 (??), the electron coupling (V), the thermal ET barrier (??G*), 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 ?? 1011 s-1 at 298 K, yielding ??Ga?? = 420 cm -1 (the activation free energy from the Eyring plot) for the und erlying process.
