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Phase transitions of organic crystals caused by conformational changes of alkyl chains : observation of intermediate stages with a temperature-resolved single crystal diffraction method

由烷基链构象变化引起的有机晶体的相变：用温度分辨单晶衍射法观察中间阶段

基本信息

批准号：
12640490
负责人：
IWASAKI Fujiko
金额：
$ 1.98万
依托单位：
The University of Electro-Communications
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (C)
财政年份：
2000
资助国家：
日本
起止时间：
2000 至 2002
项目状态：
已结题

项目摘要

Very few studies have been done on the detailed structural changes during transitions, because of the crystal damage and difficulties of intensity measurements for single crystal structure analyses at various temperatures. Recently, temperature-resolved structure analyses became possible through the development of diffractometers with two-dimensional detectors. Crystals of acridin-N-oxyl derivatives with a long alkyl chain (CnH2n+1, n=12, 13) showed that the first order. In the case of the n=13, the single crystalline states were kept during the transition. Structure analyses were carried out every 2 K during the transition from 264 to 252 K and at 295, 280, 273, 244 and 100 K. Crystals of a acylurea derivative, iso-C_5H_<11>-CO-NH-CO-NH-C_2H_5 showed a phase transition at 367K (mp=378 K) and also kept single-crystalline-state during the transition. Structure analyses were performed at 98, 298, 328 K and in the range of 348 ~ 374 K every 2 K. For Crystals ClCH_2-CO-NH-CO-NH-C_5H_<11>, … More powder diffraction method was performed because of crystalline damage. In these crystals, intermediate stages and mechanism of phase transitions caused by the conformational changes of alkyl groups induced by the thermal expansion was revealed. A pentacoordinated boron compound bearing 1, 8-dimethoxyanthracene and dithiocatecholato ligands showed the second-order phase transition, Pnma at high temperature phase and P2_12_12_1 at low temperature phase. Temperature-dependent structure analyses were performed every 2 K during phase transition. Following the thermal expansion, the catecholate moieties begin to librate even from 120 K and become disordered at 203 K. Intermolecular energies were calculated using simple force field potentials for the neighboring molecular pairs at each temperature. The energy barrier between ordered and disordered structures at the transition point was estimated about 1 kJ/molX-ray crystal structure analysis 2 temperature-resolved X-ray structure analysis (3) phase transition 4) organic crystals (5) powder diffraction method (6 acylurea 7 acridin-N-oxyl derivatives (8) pentacoordinated boron compound Less

由于晶体损伤和不同温度下单晶结构分析的强度测量困难，很少有人对转变过程中的详细结构变化进行研究。最近，通过开发具有二维探测器的衍射仪，温度分辨结构分析成为可能。长烷基吖啶-N-氧自由基衍生物（CnH_（2n +1），n=12，13）的晶体结构为一级反应。在n=13的情况下，在转变期间保持单晶状态。在264 - 252 K的转变过程中，每隔2 K以及在295、280、273、244和100 K下进行结构分析。酰脲衍生物iso-C_5 H_<11>-CO-NH-CO-NH-C_2H_5的晶体在367 K（mp=378 K）发生相变，并在相变过程中保持单晶状态。在98、298、328 K和348 ~ 374 K范围内每隔2 K进行结构分析。对于ClCH_2-CO-NH-CO-NH-C_5H_2晶体<11>， ...更多信息由于晶体损伤，进行粉末衍射法。在这些晶体中，由热膨胀引起的烷基构象变化引起的相变的中间阶段和机制被揭示。含1，8-二甲氧基蒽和二硫代邻苯二酚的五配位硼化合物具有二级相变，高温相为Pnma，低温相为P2_12_12_1。在相变过程中，每隔2 K进行一次温度相关的结构分析。随着热膨胀，儿茶酚酯部分甚至从120 K开始开始振动，并在203 K变得无序。在每个温度下，使用简单的力场势为相邻的分子对计算分子间的能量。转变点处有序和无序结构之间的能垒估计约为1 kJ/mol X射线晶体结构分析2温度分辨X射线结构分析（3）相变4）有机晶体（5）粉末衍射法（6酰基脲7吖啶-N-氧基衍生物（8）五配位硼化合物减