Electronic structure and dynamics of the excited state in CT microcrystals as revealed by femtosecond diffuse reflectance spectroscopy

Tsuyoshi Asahi, Yasutaka Matsuo, Hiroshi Masuhara*, Hideko Koshima

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

26 Scopus citations

Abstract

Transient absorption spectra of charge-transfer (CT) crystals between methyl- or methoxy-substituted benzene derivatives and pyromellitic dianhydride (PMDA) were measured by femtosecond diffuse reflectance spectroscopy, and the electronic structure and dynamics of the excited state depending on the nature of the electron donor (D) are discussed. For such weak CT complexes, it was confirmed that excitation energy is localized in one donor-acceptor pair and the mixing of CT and locally excited (LE) configurations is important in the excited CT singlet state. The CT degree of the excited state depends on the oxidation potential of D and on the mutual configuration of D and electron acceptor (A) molecules. The second-order decay constant of the excited state was observed under usual photolysis conditions, from which a motion-limited diffusion was considered. A first-order decay of the transient absorption was obtained, when the excitation intensity was weak, and ascribed to charge recombination to the ground state. The energy gap (-ΔG) dependence of the charge recombination rate constant (kCR) was confirmed to give a linear relationship between ln(kCR) and |-ΔG|.

Original languageEnglish
Pages (from-to)612-616
Number of pages5
JournalJournal of Physical Chemistry A
Volume101
Issue number4
DOIs
StatePublished - 23 Jan 1997

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