Christensen Ronald L, Barney Elizabeth A, Broene Richard D, Galinato Mary Grace I, Frank Harry A
Department of Chemistry, Bowdoin College, Brunswick, ME 04011-8466, USA.
Arch Biochem Biophys. 2004 Oct 1;430(1):30-6. doi: 10.1016/j.abb.2004.02.026.
We have developed procedures for synthesizing dimethyl polyenes using living polymerization techniques and have initiated investigations of the spectroscopic properties of these molecules. Purification using high-performance liquid chromatography (HPLC) of the polyene mixtures resulting from the syntheses promises to provide all-trans polyenes with a wide range in the number of conjugated double bonds. Low temperature optical measurements on these model systems, both in glasses and in n-alkane mixed crystals, yield absorption and fluorescence spectra with considerably higher vibronic resolution than the spectra currently available for carotenoids with comparable conjugation lengths. The dimethyl polyenes thus allow a more precise exploration of the electronic properties of long, linearly conjugated systems. These studies can be used to verify the existence of low-lying singlet states predicted by theory and recently invoked to explain low-resolution fluorescence, Raman excitation spectra, and the transient absorption spectroscopy of carotenoids. Steady state and time-resolved optical studies of the dimethyl series will be used to better understand the energies and dynamics of the low energy electronic states relevant to the photochemistry and photobiology of all linearly conjugated systems.
我们已经开发出了使用活性聚合技术合成二甲基多烯的方法，并已开始对这些分子的光谱性质进行研究。通过高效液相色谱（HPLC）对合成得到的多烯混合物进行纯化，有望提供具有广泛共轭双键数量的全反式多烯。在玻璃和正构烷烃混合晶体中对这些模型体系进行低温光学测量，得到的吸收光谱和荧光光谱的振动分辨率比目前具有可比共轭长度的类胡萝卜素光谱要高得多。因此，二甲基多烯能够更精确地探索长线性共轭体系的电子性质。这些研究可用于验证理论预测的低激发单重态的存在，最近该单重态被用来解释类胡萝卜素的低分辨率荧光、拉曼激发光谱和瞬态吸收光谱。二甲基系列的稳态和时间分辨光学研究将用于更好地理解与所有线性共轭体系的光化学和光生物学相关的低能电子态的能量和动力学。
