不寻常的放松途径来自于卡罗类的双光子激发的第一单元状态
Yoonsoo Pang1, Garth A Jones, Matthew A Prantil
1Department of Chemistry, University of California, Berkeley, and Physical Biosciences Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720-1460, USA.
Journal of the American Chemical Society
|January 29, 2010
概括
研究人员使用短暂吸收和DFT计算研究了胡卜素. 他们发现了一种长寿物种,可能是胡卜素和溶剂之间的电荷转移复合体,解释了其独特的红外和可见吸收特性.
科学领域:
- 摄影化学和光谱学
- 计算化学计算化学
- 胡卜素科学 胡卜素科学
背景情况:
- 胡卜素是具有复杂兴奋状态动态的重要颜料.
- 之前的研究观察到光激发后在胡卜素中长寿的物种,但它们的性质仍然不清楚.
- 了解这些过渡物种对于阐明胡卜素光物理路径至关重要.
研究的目的:
- 为了研究长寿物种在胡卜素8'-apo-beta-caroten-8'-al和7',7'-dicyano-7'-apo-beta-carotene中的分子身份.
- 为了将实验光谱数据与理论计算相关联.
- 阐明观察到的过渡物种的形成机制和结构特征.
主要方法:
- 暂时的红外和可见吸收光谱被用来监测激发状态的物种.
- 两光子激发被用来启动光化学过程.
- 密度函数理论 (DFT) 计算,利用B3LYP/6-31G(d) 理论水平,进行了对潜在能量表面,异构体和光谱属性的建模.
主要成果:
- 观察到一种具有明显的红外吸收 (~1510 cm-1) 和可见吸收 (以760 nm为中心) 的长寿物种.
- 这种物种表现出比特指数衰变动力学 (16 ps和140270 ps),较慢的成分取决于溶剂极性.
- DFT的计算显示实验红外光谱与胡卜素离子基的计算光谱之间有很大的相似之处,尽管可见光谱并不完全匹配.
结论:
- 实验和理论数据表明,长寿物种不是一个简单的单体离子基.
- 激发的胡卜素和溶剂分子之间形成的电荷转移复合物被认为是观察到的长寿物种的起源.
- 这一发现为溶液中胡卜素的复杂光化学提供了新的见解.
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