Fluorescence of retinal Schiff base in alcohols
Fluorescence of retinal Schiff base in alcohols
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DOI：
10.1021/jp983646a
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发表时间：
1999-04-15
影响因子：
2.9
通讯作者：
Gillbro, T
中科院分区：
文献类型：
--
作者：
Bachilo, SM;Gillbro, T
研究了室温下未质子化的视黄醛正丁基席夫碱（SBR）在正醇中的荧光光谱、量子产率和动力学。虽然在H-键合溶剂中的吸收光谱相比于在己烷中的吸收仅略微向较长波长偏移，但发射光谱受到H-键形成的强烈影响。辐射S-1态寿命在100-200 ns范围内，表明S-1 → S-0跃迁是强禁戒的。随着极性的降低，S-1态衰减的速率降低，在纯醇中，该速率与介电常数呈指数关系。半经验计算表明，在激发态比在基态，这可能会导致质子化的SBR激发时，从醇到SBR的质子转移的概率更大。理论模型还表明，极性环境增加了这种质子从醇转移到SBR的可能性。观察到的实验结果可以解释由H-键合的S-1态寿命的增加。在该模型中，溶剂极性的增加使得氢键复合物中的非辐射衰减更快，这是由于质子从醇转移到SBR。
Spectra, quantum yields, and kinetics of the unprotonated n-butyl Schiff base of retinal (SBR) fluorescence are investigated in n-alcohols at room temperature. While the absorption spectra in H-bonding solvents are only slightly shifted to longer wavelengths compared to the absorption in hexane, the emission spectra are strongly influenced by H-bond formation. The radiative S-1 state lifetimes are found to be in the 100-200 ns range, indicating that the S-1 --> S-0 transition is strongly forbidden. With decreasing polarity the rate of the S-1 state decay decreases and in pure alcohols the rate exhibits an exponential dependence on the dielectric constant. Semiempirical calculations indicate a larger probability of proton transfer from alcohol to SBR in the excited state than in the ground state, which may result in protonation of the SBR upon excitation. The theoretical model also shows that the polar environment increases the probability of such a proton transfer from alcohol to SBR. The observed experimental results can be explained by an increase of the S-1 state lifetime by H-bonding. Within the model an increase of solvent polarity makes the nonradiative decay faster in the H-bonded complex due to proton transfer from the alcohol to SBR.