Bipolar Molecules with High Triplet Energies: Synthesis, Photophysical, and Structural Properties

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• 作者：Yonghao Zheng ; Andrei S. Batsanov ; Vygintas Jankus ; Fernando B. Dias ; Martin R. Bryce ; Andrew P. Monkman
• 刊名：Journal of Organic Chemistry
• 出版年：2011
• 出版时间：October 21, 2011
• 年：2011
• 卷：76
• 期：20
• 页码：8300-8310
• 全文大小：1131K
• 年卷期：v.76,no.20(October 21, 2011)
• ISSN：1520-6904

文摘

This article sheds new light on the interplay of electronic and conformational effects in luminescent bipolar molecules. A series of carbazole/1,3,4-oxadiazole hybrid molecules is described in which the optoelectronic properties are systematically varied by substituent effects which tune the intramolecular torsion angles. The synthesis, photophysical properties, cyclic voltammetric data, X-ray crystal structures, and DFT calculations are presented. Excited state intramolecular charge transfer (ICT) is observed from the donor carbazole/2,7-dimethoxycarbazole to the acceptor phenyl/diphenyloxadiazole moieties. Introducing more bulky substituents onto the diphenyloxadiazole fragment systematically increases the singlet and triplet energy levels (E_S and E_T) and blue shifts the absorption and emission bands. The triplet excited state is located mostly on the oxadiazole unit. The introduction of 2,7-dimethoxy substituents onto the carbazole moiety lowers the value of E_S, although E_T is unaffected, which means that the singlet鈥搕riplet gap is reduced (for 7bE_S 鈥?E_T = 0.61 eV). A strategy has been established for achieving unusually high triplet levels for bipolar molecules (E_T = 2.64鈥?.78 eV at 14 K) while at the same time limiting the increase in the singlet energy.