X-Ray Crystal Structure Analyses of Unstable Triplet Carbenes and Nitrenes and Comparison with their Reactivities

为了理解化学反应的机理，获得反应中间体并分析其特征是必不可少的。虽然光谱学研究已经清楚了激发分子在几个飞秒的时间尺度上的能量变化，但激发分子的结构至今仍不清楚，因为人们一直认为不可能将激发分子捕获在晶格中并通过X射线分析结构。在目前的工作中，我们打算分析的不稳定物种，如三重态卡宾和氮烯的结构。反应物分子重氮甲烷或叠氮苯的晶体在衍射仪上使用氮气流方法冷却至低于80 K，并使用导管暴露于高压汞灯。在低温下照射后收集衍射数据。在差分傅里叶图中，出现了新的峰，这些峰被指定为产生的Ca 关于我们 rbene或nitrene，虽然只有10%的反应物分子转化为不稳定的物种。计算结果与理论计算结果吻合较好。对于氮烯，由于生成的氮烯在晶格中重叠在反应物分子上，很难获得精确的结构。使用二苄胺作为主体产生主体-客体络合物。用Spring-8安装的真空照相机分析辐照过的晶体。从主客体配合物中得到了氮宾的精确结构。此外，铂络合物的晶体在80 K下暴露于氙灯。收集了辐照前和辐照过程中的衍射数据，并对两种结构进行了分析。晶格常数在辐照过程中发生了明显的变化。照射期间的结构清楚地表明，根据分子轨道理论，在激发态下Pt-Pt距离缩短。上述结果表明，X射线晶体学在分析不稳定物种中将发挥重要作用。少

In order to understand the mechanism of chemical reactions, it is essential to obtain the reaction intermediates and to analyze their characteristics. Although the spectroscopic studies have been made clear the energy change of the excited molecules in the time scale of a few femtosecond, the structures of the excited molecule have been obscure till now, since it has been considered to be impossible to trap the excited molecules in a crystalline lattice and to analyze the structures by X-rays. In the present work, we intended to analyze the structures of unstable species such as triplet carbenes and nitrenes. The crystal of the reactant molecule, diazomethane or phenylazide, was cooled below 80 K on the diffractometer using the nitrogen-gas-flow method and was exposed to the high-pressure mercury lamp using a guide tube. The diffraction data were collected after the irradiation at low temperatures. In a difference Fourier map, the new peaks appeared, which were assigned the produced ca … More rbene or nitrene, although only 10% reactant molecules were converted to the unstable species. The structures are in good agreement with those obtained from the theoretical calculation. For the nitrene, it was difficult to obtain the precise structure, since the produced nitrene overlapped on the reactant molecule in the crystalline lattice. The host-guest complex was produced using dibenzylamine as a host. The irradiated crystal was analyzed by the vacuum camera set up at Spring-8. The precise structure of the nitrene was obtained from the host-guest complex. Moreover, the crystal of a platinum complex was exposed to a xenon lamp at 80K. The diffraction data before and during the irradiation were collected and both of the structures were analyzed. The lattice constant clearly changed during the irradiation. The structure during the irradiation clearly indicated that the Pt-Pt distance is shortened at the excited state in accordance with the molecular orbital theory. A11 the above results suggest that the X-ray crystallography will play an important role in analyzing the unstable species in near future. Less