Structure Analysis of Unstable Crystals using Rapid X-ray Measurement System

1. 快速收集x射线强度数据对于确定不稳定晶体的结构尤为重要。本文研制了一种新型的x射线衍射仪（DIP-3000），它采用成像板作为二维探测器，卡帕角计和mu轴，可以在数小时内测量单晶的衍射强度。用四圆衍射仪对结构进行了性能测试和比较，结果表明，用我们的新型快速x射线测量系统所获得的强度数据的准确性是可靠的，作为普通晶体学的一种工具，该系统可以令人满意地工作，对不稳定晶体非常有用。在四圆衍射仪上，数据收集的总时间约为3 ~ 4天，而在到达晶体上，数据收集的总时间约为2 ~ 3小时。虽然R值比四圆衍射仪的R值大0.01左右，但从该设备得到的键长和键角与四圆衍射仪估计的标准偏差相当吻合。利用该装置，我们成功地测定了几种晶体极不稳定的新型金属-碳烯配合物的晶体结构。结果表明，该设备对具有大晶胞的晶体非常有用。强度数据可以在7-10小时内测量，而在四圆衍射仪上则需要10或14天。该装置还研究了有机晶体中的动态结构转变和分子运动，揭示了2,4-二硝基苯-o-茴香胺的热重排机理。

1. Rapid collection of X-ray intensity data is especially important for determining structures of unstable crystal. A new type of X-ray diffractometer (DIP-3000) has been developed with Imaging plate as a two-dimensional detector, a kappa-goniometer and a mu-axis in order to measure diffraction intensities from a single crystal within several hours.2. A performance test and comparison of structures using a four-circle diffractometer indicated that the accuracy of the intensity data taken with our new rapid X-ray measurement system are reliable and the system can work quite satisfactorily as a tool of ordinary crystallography and very useful for unstable crystals. Total time for data collection was about 2 or 3 hours for reach crystals, on the contrast to about 3 or 4 days on the four-circle diffractometer. Although R values are larger by about 0.01 than those of four-circle diffractometer, bond lengths and angles obtained from this equipment and a four-circle diffractometer agree quite well within the estimated standard deviations.3. Using this equipment we could successfully determined the crystal structures of several new metal-carbene complexes whose crystals were very unstable. It is revealed that this equipment is very useful for crystals having a large unit cell. Intensity data could be measured within 7-10 hours, on the contrast to about 10 or 14 days on the four-circle diffractometer.4. Dynamic structural transformations and molecular motion in organic crystals were also investigated using this equipment and the mechanism of thermal rearrangement in 2,4-dinitrophenyl-o-anisidine was revealed.