Variable Temperature Diffraction

我们建议为我们的单晶X射线衍射仪购买一个可变温的低温恒温器。这是NSERC支持申请人实验室创新研究所需的关键基础设施。温度对X射线的衍射具有显著影响，较低的温度导致显著增强（更强）的反射强度，并且通常更好地限定热参数。对于氟化和卤化化合物，这些温度效应变得显著，并且可导致高角度峰的温度依赖性损失，从而导致最终结构的分辨率。这可能会在审查期间以及最终出版物中对结构结果的可接受性产生影响。值得注意的是，由于收集的数据和最终模型的系统改进，低温的使用现在在许多设施中是常规的。除了这些因素之外，许多化合物经历温度依赖性相变，并且温度的控制对于确定这些相是关键的。购买的仪器是Oxford 1000低温恒温器，它取代了安装在ApexII Bruker衍射仪上的故障和不可修复的Bruker Cryostream装置。这台有20年历史的设备已经维修过两次（布鲁克），在2019年最后一次技术人员访问后被认为无法修复。该基础设施不仅将支持该应用程序的三个CoPI，还将用于每年平均培训17名HQP。它将向其他用户开放，并将支持我们目前的研究和本提案中描述的持续前线研究。

We propose to purchase a variable temperature cryostat for our single crystal X-ray diffractometer. This is a critical piece of infrastructure which is required for the NSERC supported innovative research in the applicant's labs. Temperature has a significant effect on the diffraction of x-rays with lower temperatures leading to significantly enhanced(stronger) reflection intensities, and often better defined thermal parameters. For fluorinated and halogenated compounds these temperature effects become significant and can lead to a temperature dependent loss of high angle peaks and thus resolution of the final structure. This can make a difference in the acceptability of a structure result during review and thus final publication. Significantly though, the use low temperature is now routine in many facilities due to systematic improvements in the data collected and the final models. In addition to these factors, many compounds undergo temperature dependent phase transitions and control of the temperature is critical for the determination of these phases. The instrument to be purchased is an Oxford 1000 low temperature cryostat which replace a failed and irreparable Bruker Cryostream unit fitted onto an ApexII Bruker diffractometer. This twenty year old unit has been repaired twice(by Bruker) and deemed irreparable after the last technicians visit in 2019. This infrastructure will not only support the three CoPI's of this application but be used to train an average of 17 HQP annually. It will be open to other users and it will support much our current research and the continued frontline research described in this proposal.