Self-Diffusion, Overall Rotation of Molecules, and Ring Motions in the Three Solid Phases of Formylferrocene, Fe(C5H5) (C5H4CHO), as Studied by 1H NMR and Differential Thermal Analysis

Abstract

The temperature dependences of static and rotating frame 1H spin-lattice relaxation times, T1 and T1ϱ, respectively, and also of 1H spin-spin relaxation time, T*2 were studied for formylferrocene Fe(C5H5)(C5H4CHO). Broadline 1H NMR was investigated over a wide range of temperature. Differential thermal analysis revealed a new second-order phase transition at 294 K. At 77 K, formylferrocene was found to form a rigid lattice. Above 130 K, the onset of the Cs reorientation of the cyclopentadienyl ring in the molecule about its C5 axis was observed to take place with the average activation energy of 14.5 kJ mol−1. In the plastic phase above 317 K, the uniaxial as well as overall rotations and self-diffusion of the molecule as a whole were detected to occur. Other motional parameters of the unsubstituted cyclopentadienyl rings and the molecules in each phase were evaluated.