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首页> 外文期刊>The journal of physical chemistry, A. Molecules, spectroscopy, kinetics, environment, & general theory >Conformational Switching in Pyruvic Acid Isolated in Ar and N-2 Matrixes: Spectroscopic Analysis, Anharmonic Simulation, and Tunneling
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Conformational Switching in Pyruvic Acid Isolated in Ar and N-2 Matrixes: Spectroscopic Analysis, Anharmonic Simulation, and Tunneling

机译：Ar和N-2基质中丙酮酸的构象转换：光谱分析，非谐模拟和隧穿

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摘要

Monomers of pyruvic acid (PA) isolated in cryogenic argon and nitrogen matrixes were characterized by mid- and near-infrared spectroscopy. Interpretation of the experiments was aided by fully anharmonic calculations of the fundamental modes, overtones, and combinations up to two quanta, including their infrared intensities. The initially dominating PA conformer (Tc) has a cis CCOH arrangement and is stabilized by a strong intramolecular H-bond. Selective near-infrared excitation of Tc at the first OH overtone (6630 cm(-1) in Ar, 6643 cm(-1) in N-2) induced a large scale conformational conversion to the higher-energy conformer (Tt) with trans CCOH arrangement. Tt was then converted back to Tc by selective NIR irradiation at the first Tt OH overtone (6940 cm(-1) in Ar, 6894 cm(-1) in N-2). In N-2 matrix, the Tt form was stabilized due to interaction between the OH group and the matrix molecules. This stabilization manifested itself in the absence of Tt -> Tc relaxation and in a considerable change of the vibrational Tt signature upon going from argon to nitrogen matrix. In argon, the Tt form spontaneously decayed back to Tc in the dark (characteristic lifetime +16 h). In the presence of broad-band near-infrared light, the Tt -> Tc relaxation speed considerably increased. The decay mechanisms are discussed.
机译：通过中红外和近红外光谱对低温氩和氮基质中分离的丙酮酸（PA）单体进行了表征。基本模态，泛音和最多两个量子的组合（包括其红外强度）的完全非谐计算有助于实验的解释。最初占优势的PA构象异构体（Tc）具有顺式CCOH排列，并通过强分子内H键稳定。 Tc在第一个OH泛音（Ar中为6630 cm（-1），N-2中为6643 cm（-1））的选择性近红外激发导致大规模构象转化为具有反式的高能构象体（Tt） CCOH安排。然后通过在第一个Tt OH泛音（Ar中为6940 cm（-1），N-2中为6894 cm（-1））进行选择性NIR辐照，将Tt转换回Tc。在N-2基质中，由于OH基团与基质分子之间的相互作用，Tt形式得以稳定。这种稳定表现在没有Tt-> Tc弛豫以及从氩气到氮气基体时振动Tt信号的显着变化中。在氩气中，Tt形式在黑暗中（特性寿命+16小时）自发地退回到Tc。在宽带近红外光的存在下，Tt-> Tc弛豫速度大大提高。讨论了衰减机理。

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