Calorimetric studies on phase transitions arising from orientational order-disorder of the molecular axes of ferrocene and its derivatives |
| |
| Institution: | 1. Department of Chemistry, Birla Institute of Technology and Science, Pilani 333 031, Rajasthan, India;2. Department of Biological Sciences, Birla Institute of Technology and Science, Pilani 333 031, Rajasthan, India;1. Department of Chemistry, Indian Institute of Technology Gandhinagar, Palaj, Gandhinagar 382055, India;2. Deparment of Physics, Indian Institute of Technology, Gandhinagar Palaj, Gandhinagar, Gujarat 382055, India;3. Deparment of Biological Engineering, Indian Institute of Technology, Gandhinagar Palaj, Gandhinagar, Gujarat 382055, India;1. Key Laboratory for Advanced Materials and Feringa Nobel Prize Scientist Joint Research Center, Frontiers Science Center for Materiobiology and Dynamic Chemistry, School of Chemistry and Molecular Engineering, East China University of Science and Technology, Meilong Road 130, Shanghai 200237, China |
| |
| Abstract: | Heat capacities of the channel inclusion compound, Fe(C5D5)2 · 3(NH2)2CS, and two ferrocenium salts, Fe(C5H5)(C6H6)]+ (PF6)− and Fe(C5H5)2]+ (PF6)−, have been measured with adiabatic calorimeters between 13 and 393 K. Five phase transitions were found for Fe(C5D5)2 · 3(NH2)2CS corresponding to those for Fe(C5H5)2 · 3(NH2)2CS. The dominant phase transitions at 145.8 and 160.6 K are responsible for the onset of reorientational order-disorder of the molecular axis of Fe(C5D5)2 in the clathrate cavity. The mass-effect of the guest ferrocene molecule on the phase transitions was not remarkable. The ferrocenium salt, Fe(C5H5)(C6H6]+(PF6)−, exhibited four phase transitions and two glass transition phenomena at low temperatures while its analog, Fe(C5H5)2]+(PF6)−, brought about only three phase transitions without showing the glass transition. The higher-temperature phase transitions in these two salts have been assigned to the reorientational order-disorder mechanism of the molecular axes of the cations in the pseudo-cavities formed by eight PF−6 anions. For the origin of the lower-temperature phase transitions in these two salts, three possibilities have been discussed. Among them, plausible origin is likely to be an order-disorder change of PF−6 anion in the lattice. An important unsettled problem common to these three compounds is a question whether or not the Fe(C5D5)2 and the cations, Fe(C5H5)(C6H6)]+ and Fe(C5H5)2]+, are still reorienting around their molecular axes even at the lowest-temperature phase. |
| |
| Keywords: | |
| 本文献已被 ScienceDirect 等数据库收录！ |
|
