Investigating Intramolecular H Atom Transfer Dynamics in β-Diketones with Ultrafast Infrared Spectroscopies and Theoretical Modeling
Investigating Intramolecular H Atom Transfer Dynamics in β-Diketones with Ultrafast Infrared Spectroscopies and Theoretical Modeling
复制标题
用超快红外光谱和理论模型研究β-二酮中的分子内氢原子转移动力学
DOI：
10.1021/acs.jpca.3c05417
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发表时间：
2023
期刊：
影响因子：
--
通讯作者：
Fournier, Joseph A.
中科院分区：
文献类型：
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作者：
Dean, Jessika L.S.;Winkler, Valerie S.;Boyer, Mark A.;Sibert, Edwin L.;Fournier, Joseph A.
利用二维红外光谱和计算模型研究了一系列β-二酮分子内氢键的振动特征和超快动力学。所选的β-二酮显示出一定范围的H原子给体-受体距离和沿H原子转移坐标的沿着不对称性，从而调节分子内氢键强度。具有最强的H-键的物种被计算为具有非常软的H原子势，导致高度红移的OH伸缩基频和位错的H原子振动激发后。这些软势导致显着耦合到其他正常模式坐标，并引起实验观察到的非常广泛的振动签名。在轻和氘同位素的OH和OD伸缩区域的二维红外光谱揭示了振动热分子的加宽和长寿命的基态漂白特征。在OH和OD拉伸区域的偏振敏感的瞬态吸收测量显示取向动力学显着的同位素差异。取向弛豫测量发生在600 fs和200 ps的时间尺度上的轻和氘同位素，分别。取向动力学解释在激活H/D原子转移事件驱动的集体分子内结构重排。
The vibrational signatures and ultrafast dynamics of the intramolecular H-bond in a series of β-diketones are investigated with 2D IR spectroscopy and computational modeling. The chosen β-diketones exhibit a range of H atom donor–acceptor distances and asymmetry along the H atom transfer coordinate that tunes the intramolecular H-bond strength. The species with the strongest H-bonds are calculated to have very soft H atom potentials, resulting in highly red-shifted OH stretch fundamental frequencies and dislocation of the H atom upon vibrational excitation. These soft potentials lead to significant coupling to the other normal mode coordinates and give rise to the very broad vibrational signatures observed experimentally. The 2D IR spectra in both the OH and OD stretch regions of the light and deuterated isotopologues reveal broadened and long-lived ground-state bleach signatures of the vibrationally hot molecules. Polarization-sensitive transient absorption measurements in the OH and OD stretch regions reveal notable isotopic differences in orientational dynamics. Orientational relaxation was measured to occur on ∼600 fs and ∼2 ps time scales for the light and deuterated isotopologues, respectively. The orientational dynamics are interpreted in terms of activated H/D atom transfer events driven by collective intramolecular structural rearrangements.