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首页> 外文期刊>The journal of physical chemistry, A. Molecules, spectroscopy, kinetics, environment, & general theory >Spectral and Photophysical Behavior of Cytisine in n-Hexane. Experimental Evidence for the S-1(n,pi*) -> S-0 Fluorescence
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Spectral and Photophysical Behavior of Cytisine in n-Hexane. Experimental Evidence for the S-1(n,pi*) -> S-0 Fluorescence

机译：正己烷中细胞素的光谱和光学性能。 S-1（N，PI *） - > S-0荧光的实验证据

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摘要

Spectral and photophysical properties of (-)-cytisine (the compound used as a smoking cessation aid and a potential drug in Alzheimer's and Parkinson's diseases) were investigated. The two conformers of cytisine, whose presence in the S-0 state has been earlier proved by the NMR and IR methods as well as in theoretical calculation, in nonpolar n-hexane show a rarely observed prompt fluorescence from the s(1)(n,pi*) excited state. This observation is unambiguously evidenced by very small radiative rate constants of these two emitting conformers, k(F) = 7.4 x 10(5) and 3.0 X 10(5) s(-1). Their lifetimes in the S-1(n,pi*) state are relatively long, iota(s1) = 1.9 and 6.7 ns; therefore, their fluorescence quantum yield is relatively high phi(F) similar to 10(-3). The long wavelength band in the cytisine absorption originates from the excitation to the S-2(pi,pi*) state, while the S-1(n,pi*) state is not observed in this spectrum. Thus, the excited state S-2(pi,pi*) is manifested only in the absorption spectrum, while the excited state S-1(n,7r*) is seen only in the fluorescence spectrum, so cytisine in n-hexane is characterized by close lying (n,pi*) and (pi,pi*) excited singlet states.
机译：（ - Cytisine的光谱和光学性质（用作吸烟戒烟的化合物和阿尔茨海默氏症和帕金森病患者的潜在药物）。通过NMR和IR方法以及在理论计算中提前证明了S-0状态的三种细胞蜂壳，其在非极性正己烷中，己烷显示出来自S（1）的很少观察到的提示荧光（n ，pi *）兴奋状态。通过这两个发射符合特的非常小的辐射速率常数，k（f）= 7.4×10（5）和3.0×10（5）s（-1），通过非常小的辐射速率常数明确证明了该观察。它们在S-1（n，pi *）状态下的寿命相对较长，iota（s1）= 1.9和6.7 ns;因此，它们的荧光量子产率为相对较高的PHI（F），其类似于10（-3）。细胞苷吸收中的长波长带源自S-2（PI，PI *）状态的激发，而在该光谱中未观察到S-1（N，PI *）状态。因此，仅在吸收光谱中表现出激发态S-2（PI，PI *），而仅在荧光光谱中仅观察激发态S-1（N，7R *），因此N-己烷中的细胞苷是特征在于闭合（n，pi *）和（pi，pi *）激发单态状态。

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