Direct observation of the structural deformation in the intramolecular charge-transfer reaction by means of transient infrared spectroscopy

利用瞬态红外光谱直接观察分子内电荷转移反应中的结构变形

• 批准号: 16550004
• 负责人: ISHIKAWA Haruki
• 金额: $ 2.37万
• 依托单位: Kobe University
• 依托单位国家: 日本
• 项目类别: Grant-in-Aid for Scientific Research (C)
• 财政年份: 2004
• 资助国家: 日本
• 起止时间: 2004 至 2005
• 项目状态: 已结题
• 来源: https://kaken.nii.ac.jp/en/grant/KAKENHI-PROJECT-16550004/
• 关键词: Intramolecular charge-transfer reaction; torsional deformation; transient IR spectroscopy; solvated cluster; solvent re-orientation; 分子内電荷移動; フェニルジシラン; 分子軌道計算; クラスター

The intramolecular charge-transfer (ICT) reaction is one of important processes in photochemical reactions. The structural deformation, especially a torsional deformation around a single bond which connects a charge donating- and accepting groups, has been one of the central issues in understanding the ICT reaction. In the present study, we have determined the equilibrium structure of the charge-transfer (CT) state of cyanophenyldisilane (CPDS) molecule by means of the transient infrared absorption spectroscopy. We recorded the transient IR spectra of the CT state in the CH stretching region. It was revealed that the disilanyl group lies in the same plane as the phenyl ring in the CT state, while the disilanyl group is in a perpendicular plane to the phenyl ring in the laser-excited LE state. This result clearly showed that the torsional deformation proposed actually happens in the ICT reaction. This is the first direct evidence of the torsional deformation in the ICT reaction. In addition to the structural deformation of a solute itself, re-orientation processes of solvent molecules are also very important in the ICT reaction. The CT state is energetically stabilized by the re-orientation of solvents. Such stabilization is frequently discussed in interpreting a large Stokes shift of the CT emission. In the present study, we observed transient IR spectra in the OH and CN stretching region of CPDS-water cluster. It was found that the ICT reaction proceeds in two-step, like as LE→CT1→CT2. In the case of the OH stretch, a large shift of ν_<OH> was observed, while that of ν_<CN> was very small. This means that a transition from the CT1 to CT2 states is a re-orientation process of water molecule with respect to CPDS rather than an electronic transition. Our observation should provide us with a new insight of the microscopic salvation.

分子内电荷转移反应是光化学反应的重要过程之一。结构变形，特别是连接电荷供体和接受基团的单键周围的扭转变形，一直是理解ICT反应的核心问题之一。本研究利用瞬态红外吸收光谱测定了氰苯二硅烷（CPDS）分子的电荷转移态的平衡结构。我们在CH拉伸区记录了CT态的瞬态红外光谱。结果表明，在CT态下，二苯胺基与苯环在同一平面上，而在激光激发LE态下，二苯胺基与苯环在垂直平面上。这一结果清楚地表明，所提出的扭转变形实际上发生在ICT反应中。这是ICT反作用力中扭转变形的第一个直接证据。除了溶质本身的结构变形外，溶剂分子的重新取向过程在ICT反应中也非常重要。溶剂的重定向使CT态能量稳定。这种稳定性在解释CT发射的大斯托克斯位移时经常被讨论。在本研究中，我们观察了cpds -水簇OH和CN拉伸区的瞬态红外光谱。结果表明，ICT反应呈两步进行，如LE→CT1→CT2。在OH拉伸的情况下，ν_<OH>的位移很大，而ν_<CN>的位移很小。这意味着从CT1到CT2状态的转变是水分子相对于CPDS的重新定向过程，而不是电子转变。我们的观察应该为我们提供微观救赎的新见解。

项目成果

Determination of the Equilibrium Structure of the Charge-transfer State of (p-Cyanophenyl)pentamethyldisilane by Means of Transient Infrared Spectroscopy

瞬态红外光谱法测定(对氰基苯基)五甲基二硅烷电荷转移态的平衡结构

• 发表时间: 2005
• 期刊: Journal of Physical Chemistry A 109(40)
• 作者: Y.Iiduka;O.Ikenaga;A.Sakuraba;T.Wakahara;T.Tsuchiya;他4名;V.Ya.Lee;Masaaki Nakamoto;Wataru Setaka;Son. Thanh Phan;Haruki Ishikawa;Wataru Setaka;Wataru Setaka;Wataru Setaka;Haruki Ishikawa
• 通讯作者: Haruki Ishikawa