Carborane Dyads for Photoinduced Electron Transfer: Photophysical Studies on Carbazole and Phenyl-o-carborane Molecular Assemblies
- Authors
- Kwon, Soonnam; Wee, Kyung-Ryang; Cho, Yang-Jin; Kang, Sang Ook
- Issue Date
- 12-5월-2014
- Publisher
- WILEY-V C H VERLAG GMBH
- Keywords
- carboranes; charge transfer; donor-acceptor systems; electron transfer; photochemistry
- Citation
- CHEMISTRY-A EUROPEAN JOURNAL, v.20, no.20, pp.5953 - 5960
- Indexed
- SCIE
SCOPUS
- Journal Title
- CHEMISTRY-A EUROPEAN JOURNAL
- Volume
- 20
- Number
- 20
- Start Page
- 5953
- End Page
- 5960
- URI
- https://scholar.korea.ac.kr/handle/2021.sw.korea/98523
- DOI
- 10.1002/chem.201304474
- ISSN
- 0947-6539
- Abstract
- o-Carborane-based donor-acceptor dyads comprising an o-carboranyl phenyl unit combined with N-carbazole (1) or 4-phenyl-N-carbazole (2) were prepared, and their dyad characters were confirmed by steady-state photochemistry and photodynamic experiments as well as electrochemical studies. The absorption and electrochemical properties of the dyads were essentially the sum of those of the carbazole and o-carboranyl phenyl units; this indicates negligible interaction between the carbazole and o-carborane units in the ground state. However, the emission spectra of 1 and 2 indicated that carbazole fluorescence was effectively quenched and a new charge-transfer (CT) emission was observed in solvents, varying from hexane to acetonitrile, which exhibited large Stoke shifts. The CT emission properties of o-carborane-based dyads were further analyzed by using Lippert-Mataga plots to show that unit charge separation occurred to form a charge-separated species in the excited state, namely, 12. This excited-state species was confirmed by nanosecond transient absorption spectra and spectroelectrochemical measurements; the photoexcitation of carbazole generated the CT state in which a radical cation and anion were formed at the carbazole and o-carborane units, respectively, within a few nanoseconds. DFT calculations corroborated the presence of this CT species and showed localized populations of the highest singly occupied molecular orbital on 2 in the reduced anionic state. As a result, molecular assemblies formed by linking the carbazole group with the o-carborane cage through a phenylene or multi-phenylene spacer revealed that the photoinduced electron-transfer process occurred intramolecularly.
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Collections - Graduate School > Department of Advanced Materials Chemistry > 1. Journal Articles
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