Krystkowiak Ewa, Przybył Anna K, Bayda Małgorzata, Józkowiak Julia, Maciejewski Andrzej
Faculty of Chemistry, Adam Mickiewicz University in Poznań , Umultowska 89b, 61-614 Poznań, Poland.
Center for Ultrafast Laser Spectroscopy, Adam Mickiewicz University in Poznań , Umultowska 85, 61-614 Poznań, Poland.
J Phys Chem A. 2017 Aug 3;121(30):5597-5604. doi: 10.1021/acs.jpca.7b02280. Epub 2017 Jul 25.
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 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(n,π*) excited state. This observation is unambiguously evidenced by very small radiative rate constants of these two emitting conformers, k = 7.4 × 10 and 3.0 × 10 s. Their lifetimes in the S(n,π*) state are relatively long, τ = 1.9 and 6.7 ns; therefore, their fluorescence quantum yield is relatively high ϕ ∼ 10. The long-wavelength band in the cytisine absorption originates from the excitation to the S(π,π*) state, while the S(n,π*) state is not observed in this spectrum. Thus, the excited state S(π,π*) is manifested only in the absorption spectrum, while the excited state S(n,π*) is seen only in the fluorescence spectrum, so cytisine in n-hexane is characterized by close lying (n,π*) and (π,π*) excited singlet states.
研究了（-）-金雀花碱（用作戒烟辅助药物以及治疗阿尔茨海默病和帕金森病的潜在药物的化合物）的光谱和光物理性质。金雀花碱的两种构象异构体，其在S态的存在已通过核磁共振和红外光谱方法以及理论计算得到证实，在非极性正己烷中显示出从S(n,π*)激发态发出的罕见的即时荧光。这一观察结果通过这两种发射构象异构体非常小的辐射速率常数k = 7.4 × 10和3.0 × 10 s得到明确证明。它们在S(n,π*)态的寿命相对较长，τ = 1.9和6.7 ns；因此，它们的荧光量子产率相对较高，ϕ ∼ 10。金雀花碱吸收光谱中的长波长带源于激发到S(π,π*)态，而在此光谱中未观察到S(n,π*)态。因此，激发态S(π,π*)仅在吸收光谱中表现出来，而激发态S(n,π*)仅在荧光光谱中可见，所以正己烷中的金雀花碱的特征是具有紧邻的(n,π*)和(π,π*)激发单重态。
