Electric Dipole Transition Moments and Solvent-Dependent Interactions of Fluorescent Boron鈥揘itrogen Substituted Indole Derivatives
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- 作者：Mari Saif ; Julia R. Widom ; Senmiao Xu ; Eric R. Abbey ; Shih-Yuan Liu ; Andrew H. Marcus
- 刊名：Journal of Physical Chemistry B
- 出版年：2015
- 出版时间：June 25, 2015
- 年：2015
- 卷：119
- 期：25
- 页码：7985-7993
- 全文大小：427K
- ISSN：1520-5207
文摘
Fluorescent analogues of the indole side chain of tryptophan can be useful spectroscopic probes of protein鈥損rotein and protein鈥揇NA interactions. Here we present linear dichroism and solvent-dependent spectroscopic studies of two fluorescent analogues of indole, in which the organic C鈺怌 unit is substituted with the isosteric inorganic B鈥揘 unit. We studied the so-called 鈥渆xternal鈥?BN indole, which has C2v symmetry, and the 鈥渇used鈥?BN indole with Cs symmetry. We performed a combination of absorption and fluorescence spectroscopy, ultraviolet linear dichroism (UV-LD) in stretched poly(ethylene) (PE) films, and quantum chemical calculations on both BN indole compounds. Our measurements allowed us to characterize the degree of alignment for both molecules in stretched PE films. We thus determined the orientations and magnitudes of the two lowest energy electric dipole transition moments (EDTMs) for external BN indole, and the two lowest energy EDTMs for fused BN indole within the 30鈥?00鈥?5鈥?00 cm鈥? spectral range. We compared our experimental results to those of quantum chemical calculations using standard density functional theory (DFT). Our theoretical predictions for the low-energy EDTMs are in good agreement with our experimental data. The absorption and fluorescence spectra of the external and the fused BN indoles are sensitive to solvent polarity. Our results indicate that the fused BN indole experiences much greater solvation interactions with polar solvents than does the external BN indole.