Etude par Calorimetrie,Diffraction des Rayons X et Diffusion Raman d'une Transition de Phase dans (C4 H4P) Mn (CO)3 |
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| Authors: | O Poizat C Sourisseau G Calvarin K Chhor C Pommier |
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| Institution: | 1. Laboratoire de Spectrochimie infrarouge et Raman , CNRS , 2, rue Henri Dunant, 94320, Thiais, France;2. Equipe de recherche associée au CNRS n° 456, Laboratoire de Chimie Physique du Solide , Ecole Centrale des Arts et Manufactures , 92290, Chatenay-Malabry, France;3. Laboratoire de Spectrochimie infrarouge et Raman , CNRS , 2, rue Henri Dunant, 94320, Thiais, France;4. Laboratoire de Chimie Physique , C. S. P., Université Paris Nord , 93430, VILLETANEUSE, France |
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| Abstract: | Abstract Heat capacity measurements (95-300K), X-ray diffraction (78-300K) and low frequency Raman spectroscopy (10-350K) have evidenced an order-disorder phase transition in phosphacymantrene, (C4 H4P) Mn (CO)3. This transition has been characterized by a monoclinic ←→ triclinic structural change at about 110 K and by a pretransitional phenomenon. The measured transition enthalpy and entropy are 480 ± 10J.mil?1 and 4.17 ± 0.08J.K?1 mol?1, at 115 K, respectively. A complete assignment of the observed Raman bands in h4 and d4 derivatives is proposed. From the temperature dependence of frequencies, intensities and half-widths of some Raman bands we have discussed the order, the nature and the mechanism of the phase transition: intermolecular interactions appear to be mainly involved in the mechanism and an activation energy roughly equal to 2100 ± 840 J. mol?1 has been determined. |
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