Nineteen novel alkyl substituted porphyrins have been synthesized and their thermal phase behaviour has been investigated in detail. Twelve compounds showed a reversible phase transition below the isotropization temperature. From time resolved microwave conductivity (TRMC) measurements and powder X-ray diffractometry it was concluded that the molecular packing does not change significantly at the lower phase transition temperature and that the porphyrin cores occupy isolated positions. Single X-ray diffraction measurements showed that the porphyrins are arranged in a layered structure and that the space between the layers is occupied by the alkyl substituents of the pyrrole units. The phase transitions at the lower temperature were therefore identified as changes in the crystal ordering of the porphyrins.
合成了19种新型烷基取代
卟啉,并详细研究了它们的热相行为。其中12种化合物在各向同性化温度以下显示可逆的相变。通过时间分辨微波电导率(TRMC)测量和粉末X射线衍射分析得出结论:在较低的相变温度下,分子排列没有显著改变,
卟啉核心占据孤立位置。单晶X射线衍射测量显示,
卟啉呈层状排列,层间由
吡咯单元的烷基取代基占据。因此,低温下的相变被确定为
卟啉晶体有序性的变化。