How Intramolecular Vibrational Energy Transport Changes with Rigidity and Polarity of the Environment?
How Intramolecular Vibrational Energy Transport Changes with Rigidity and Polarity of the Environment?
复制标题
分子内振动能量输运如何随环境的刚性和极性变化？
DOI：
10.1134/s0018143920060120
复制
发表时间：
2020-11-01
影响因子：
0.7
通讯作者：
Rubtsov, I. V.
中科院分区：
文献类型：
--
作者：
Rubtsova, N. I.;Lin, Zhiwei;Rubtsov, I. V.
通过低聚聚乙二醇（PEG）链的振动能量传输可以通过光学振动链带以弹道方式发生，显示出快速且恒定的传输速度和高传输效率，从而提供了将超过1000 cm（-1）的显著能量量子传输到超过60埃的大距离的手段。我们报告如何分子内的能量传输时间，通过链传输速度，和端基冷却速率取决于环境的刚性和极性。使用二维红外（2DIR）光谱用端基标记的PEG低聚物进行实验。通过在约100 ℃激发叠氮基部分，在链的一端开始弹道能量传输。2100 cm（-1），并通过探测琥珀酰亚胺酯的羰基拉伸模式在链的另一端记录。我们发现，刚性的环境，聚苯乙烯（PS）矩阵与类似极性的解决方案，并没有改变能量传输时间，也没有通过链传输速度。这些结果表明，在温和的极性介质中，动态波动，发生在溶液中，但主要是冻结在一个固体基质中，是不是主要原因的链状态的失相，尽管存在的快速弛豫组件的解决方案。不同介质中转运时间的相似性表明，二级链结构对PEG链中的转运影响不大。溶剂极性对分子内转运有显著影响，极性DMSO中的转运效率约为100%。1.6比在非极性CCl_4或PS中小1倍。琥珀酰亚胺酯端基的冷却时间在更极性的溶剂中减少，影响等待时间依赖性形状，从而影响能量到达报告子的时间。分析了从数据中提取能量到达时间的不同方法。所观察到的溶剂极性上的通过链的运输时间的依赖关系表明存在多个波包在PEG链中传播具有不同的群速度。
Vibrational energy transport through oligomeric polyethylene glycol (PEG) chains can occur ballistically via optical vibrational chain bands, showing fast and constant transport speed and high efficiency of the transport, thus offering means to transfer significant quanta of energy, exceeding 1000 cm(-1), to large distances exceeding 60 angstrom. We report how the intramolecular energy transport time, through-chain transport speed, and end-group cooling rate depend on the rigidity and polarity of the environment. The experiments were performed with end-group labeled PEG oligomers using two-dimensional infrared (2DIR) spectroscopy. The ballistic energy transport was initiated at one end of the chain by exciting an azido moiety at ca. 2100 cm(-1) and recorded at another end of the chain by probing the carbonyl stretching mode of succinimide ester. We found that the rigidity of the environment, polystyrene (PS) matrix vs. a solution of similar polarity, did not change the energy transport times much, nor the through-chain transport speed. These results suggest that in mildly polar media, dynamic fluctuations, occurring in solution but largely frozen in a solid matrix, are not the dominant cause of the dephasing of the chain states, despite the presence of fast relaxation components in the solution. The similarity of the transport times in different media suggests that the secondary chain structure does not affect much the transport in PEG chains. The solvent polarity affected the intramolecular transport significantly: the transport efficiency in polar DMSO is ca. 1.6 fold smaller than that in nonpolar CCl4 or PS. The cooling time of the succinimide ester end group is reduced in more polar solvents affecting the waiting time dependence shape and thus the energy arrival time to the reporter. The analysis of different ways of extracting the energy arrival time from the data is presented. The observed dependences of the through-chain transport time on the solvent polarity suggests the presence of multiple wavepackets propagating in the PEG chain with different group velocities.