Excited-State Dynamics of Wurster鈥檚 Salts
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- 作者：Jakob Grilj ; Philipp Buchgraber ; Eric Vauthey
- 刊名：The Journal of Physical Chemistry A
- 出版年：2012
- 出版时间：July 19, 2012
- 年：2012
- 卷：116
- 期：28
- 页码：7516-7522
- 全文大小：348K
- 年卷期：v.116,no.28(July 19, 2012)
- ISSN：1520-5215
文摘
The excited-state dynamics of a series of Wurster鈥檚 salts (p-phenylenediamine radical cations) with different subtituents on the nitrogen atoms was investigated under a variety of experimental conditions using a combination of ultrafast spectroscopic techniques. At room temperature, the lifetime of the lowest excited state of all radical cations is on the order of 200 fs, independently of the solvent, that is, water, nitriles, alcohols, and room-temperature ionic liquid. On the other hand, all cations, except that with the bulky nitrogen substituents, become fluorescent below 120 K. The observed dynamics can be accounted for by the presence of a conical intersection between the D1 and D0 states. For the cations with a small nitrogen substituent, this conical intersection could be accessed through a twist of one amino group, as already suggested for Wurster鈥檚 Blue. However, this coordinate cannot be invoked for the cation with bulky nitrogen subtituents, and more probably, pyramidalization of the nitrogen center and/or deformation of the phenyl ring play an important role. Consequently, the excited-state dynamics of these structurally very similar Wurster鈥檚 salts involves different decay mechanisms.