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

几乎没有陈述的变化在各种温度下的某些结构上进行了详细的变化。链（CNH2N+1，n = 12，13）。 ivative，iso-c_5h_ <11> -co-nh-co- nh-c_2h_5结构分析在98、298、328 k处，在348〜374 k的范围内，每2 k -NH-C_5H_ <11>揭示了由热温度的烷基构象变化引起的相构型的阶段和机制k在热膨胀期间，即使在203 K.ntermolec ular的范围内开始使用203 k的becorder，并使用相邻的分子对在每个温度下的邻近分子对。 1 kJ/molx射线晶体结构2温度分辨的X射线结构分析（3）相跃迁4）有机晶体（5）粉末衍射法（6酰基尿素7 Acridin-n- oxyl衍生物（8）五方面的硼龙化合物较少