Study on the catalytic role of hydrogen-bond in the phtoinduoed cis【tautomer】trans isomerization of napththol

在萘酚中有两种异构体，这取决于羟基相对于萘环的取向，称为顺式和反式。这两个旋转异构体的存在最先是由Ito和他的同事利用激光光谱技术结合超音速射流提出的。后来，普拉特和他的同事通过分析喷射冷却的萘酚的旋转分辨电子光谱对它们进行了分配。从那时起，几位研究人员一直在讨论激光操纵顺式[互变构体]反式异构化的可能性。然而，到目前为止，这一点还没有实现。在这项研究中，我们的目的是在超音速射流中利用UV-IR分步激发来操纵顺式[互变构体]反式异构化以进行电子激发。首先，用可调谐的紫外光脉冲选择性地将特定的异构体激发到S_1态。红外激光脉冲进一步激发了S_1分子或团簇的X-H伸缩振动，其中X指的是…更多的是碳、氧或氮原子。输入到X-H伸缩振动的能量通过IVR立即重新分配到其他振动模式，其中一部分将流入电离坐标。如果能量大到足以克服异构化势垒，反应就会发生，产物会发出荧光。我们不仅研究了裸分子，也研究了氢键团簇，发现在所考察的能量范围内，裸分子在3510 cm^&lt；-1&gt；范围内不发生反应。另一方面，对于氢键团簇，反应发生在2900 cm^&lt；-1&gt；如此大的还原表明氢键对反应起到了催化剂的作用。此外，我们还发现，在低红外频率下，团簇中的顺反异构化反应非常有效，但由于同一异构体中氢键的离解竞争，产率随着能量的增加而迅速下降。1-和2-萘酚氢键簇合物均发生了异构化反应，势垒高度相似。在实验的同时，我们进行了密度泛函理论计算和含时密度泛函理论计算，得到了异构化势垒高度，并研究了氢键在S_0、S_1和S_2态中的作用。虽然计算预测了S_1中势垒高度的大幅度增加，但没有考虑到势垒高度对氢键形成的影响。进一步的计算正在进行中。较少

There are two isomeric forms in naphthol, depending on the orientation of hydroxyl group with respect to the naphthalene ring, which are called cis and trans. The existence of the two rotational isomers was first proposed by Ito and coworkers by uses of laser spectroscopic technique combined with a supersonic jet. Later, Pratt and coworkers assigned them by analyzing rotationally resolved electronic spectrum of jet cooled naphthol. Since then, the possibility of the laser manipulation of cis【tautomer】trans isomerization has been discussed by several researchers. Up to now, however, it has not been realized yet. In this research, we aimed to manipulate the cis【tautomer】trans isomerization for electronically excited by use of UV-IR stepwise excitation in a supersonic jet. First, a specific isomer was selectively excited to the S_1 state with a tunable UV laser pulse. The molecule or cluster in S_1 is further excited to its X-H stretching vibration by the IR laser pulse, where X refers to … More the C,O or N atom. The energy put in to the X-H stretching vibration is immediately redistributed into other vibrartional modes by IVR, and part of them will flow into the iromerization coordinate. If the energy is large enough to overcome the isomerization barrier, the reaction will occur and the product emits fluorescence.We investigated not only bare molecule but also the hydrogen-bonded clusters and found that the reaction does not occur for bare molecule within the examined energy region up to 3510 cm^<-1>. On the other hand, the reaction occurred at 2900 cm^<-1> for hydrogen-bonded clusters. Such a larger reduction indicates that H-bond acts as a catalyst for the reaction. Furthermore, we fond in the clusters the cis-trans isomerization occurs very efficiently at low IR frequency but the yield decrease rapidly with the energy due to the competition with the dissociation of H-bond within the same isomer. The isomerization occurred both 1- and 2-napthol H-bonded clusters and the barrier height seems to be similar between them. Parallel to the experiments, we performed DFT and time-dependent DFT calculation to obtain the isomerization barrier height and to investigate the effect of H-bond in S_0, S_1 and S_2 states. Thought the calculation predicted large increase of the barrier height in S_1, it failed the decrease of the height upon the H-bond formation. Further calcuation is in progress. Less