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首页> 外文期刊>Chemistry: A European journal >Multiple Decay Mechanisms and 2D-UV Spectroscopic Fingerprints of Singlet Excited Solvated Adenine-Uracil Monophosphate
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Multiple Decay Mechanisms and 2D-UV Spectroscopic Fingerprints of Singlet Excited Solvated Adenine-Uracil Monophosphate

机译：单重态激发的溶剂化腺嘌呤-尿嘧啶单磷酸酯的多重衰变机理和2D-UV光谱指纹图谱

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摘要

The decay channels of singlet excited adenine uracil monophosphate (ApU) in water are studied with CASPT2//CASSCF: MM potential energy calculations and simulation of the 2D-UV spectroscopic fingerprints with the aim of elucidating the role of the different electronic states of the stacked conformer in the excited state dynamics. The adenine L-1(a) state can decay without a barrier to a conical intersection with the ground state. In contrast, the adenine L-1(b) and uracil S(U) states have minima that are separated from the intersections by sizeable barriers. Depending on the backbone conformation, the CT state can undergo inter-base hydrogen transfer and decay to the ground state through a conical intersection, or it can yield a long-lived minimum stabilized by a hydrogen bond between the two ribose rings. This suggests that the L-1(b), S(U) and CT states of the stacked conformer may all contribute to the experimental lifetimes of 18 and 240 ps. We have also simulated the time evolution of the 2D-UV spectra and provide the specific fingerprint of each species in a recommended probe window between 25000 and 38 000 cm(-1) in which decongested, clearly distinguishable spectra can be obtained. This is expected to allow the mechanistic scenarios to be discerned in the near future with the help of the corresponding experiments. Our results reveal the complexity of the photophysics of the relatively small ApU system, and the potential of 2DUV spectroscopy to disentangle the photophysics of multichromophoric systems.
机译：用CASPT2 // CASSCF研究了单重激发的腺嘌呤单磷酸腺嘌呤单磷酸（ApU）在水中的衰减通道：MM势能计算和2D-UV光谱指纹模拟，目的是阐明堆叠的不同电子态的作用构象态处于激发态动力学。腺嘌呤的L-1（a）状态可以衰变，而不会与基态的圆锥形相交产生障碍。相比之下，腺嘌呤L-1（b）和尿嘧啶S（U）状态的最小值与交叉点之间存在较大的障碍。取决于骨架构象，CT状态可以经历碱基间的氢转移并通过圆锥形相交处衰减为基态，或者它可以产生通过两个核糖环之间的氢键稳定的长寿命最小值。这表明堆叠构象异构体的L-1（b），S（U）和CT状态可能都有助于18 ps和240 ps的实验寿命。我们还模拟了2D-UV光谱的时间演变，并在25000至38 000 cm（-1）之间的推荐探针窗口中提供了每种物种的特定指纹，在该窗口中可以获得充血，清晰可辨的光谱。预期这将在相应的实验帮助下在不久的将来识别机械方案。我们的结果揭示了相对较小的ApU系统的光物理的复杂性，以及2DUV光谱学有可能解开多发色系统的光物理。

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