Excited-state behavior of N-phenyl-substituted trans-3-aminostilbenes: Where the "m-amino effect" meets the "amino-conjugation effect"

Jye Shane Yang, Kang Ling Liau, Chi Wei Tu, Chung Yu Hwang

研究成果: 雜誌貢獻期刊論文同行評審

31 引文 斯高帕斯(Scopus)

摘要

The electronic spectroscopy and photochemistry of the trans isomers of 3-(N-phenylamino)stilbene (m1c), 3-(N-methyl-N-phenylamino)stilbene (m1d), 3-(N,N-diphenylamino)stilbene (m1e), and 3-(N-(2,6-dimeth-ylphenyl)amino) stilbene (m1f) and their double-bond constrained analogues m2a-m2c and m2e are reported. When compared with trans-3-aminostilbene (m1a), m1c-m1e display a red shift of the S0 → S1 absorption and fluorescence spectra, lower oscillator strength and fluorescence rate constants, and more efficient S1 → T1 intersystem crossing. Consequently, the N-phenyl derivatives m1c-m1e have lower fluorescence quantum yields and higher photoisomerization quantum yields. The corresponding N-phenyl substituent effect in m2a-m2e is similar in cyclohexane but smaller in acetonitrile. This is attributed to the weaker intramolecular charge transfer character for the S1 state of m2 so that the rates for intersystem crossing are less sensitive to solvent polarity. It is also concluded that N-phenyl substitutions do not change the triplet mechanism of photoisomerization for m1 in both nonpolar and polar solvents. Therefore, the "m-amino conjugation effect" reinforces the "m-amino effect" on fluorescence by further reducing its rate constants and highlights the N-phenyl-enhanced intersystem crossing from the "amino-conjugation effect" by making S1 → T1 the predominant nonradiative decay pathway.

原文???core.languages.en_GB???
頁(從 - 到)6450-6456
頁數7
期刊Journal of Physical Chemistry A
109
發行號29
DOIs
出版狀態已出版 - 28 7月 2005

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