Estimate of the vibrational contribution to the entropy change associated with the spin transition in the d4 systems [MnIII(pyrol)3tren] and [CrII(depe)2I2].
(2007) Physical chemistry chemical physics : PCCP — Vol. 9, n° 10, p. 1194-1201 (2007)
Files
No attached file found for this publication.
Details
- Authors
- Abstract
- The vibrational contribution to DeltaS of the low-spin ((3)T(1)) to high-spin ((5)E) spin transition in two 3d(4) octahedral systems [Mn(III)(pyrol)(3)tren] and [Cr(depe)(2)I(2)] have been estimated by means of DFT calculations (B3LYP/CEP-31G) of the vibrational normal-modes frequencies. The obtained value at the transition temperature for the Mn(iii) complex is DeltaS(vib)(44 K) = 6.3 J K(-1) mol(-1), which is comparable with the proposed Jahn-Teller contribution of R ln3 = 9.1 J K(-1) mol(-1) and which is approximately half of the experimentally determined 13.8 J K(-1) mol(-1). The corresponding value for the Cr(ii) complex is DeltaS(vib)(171.45 K) = 46.5 J K(-1) mol(-1), as compared to the experimental value of 39.45 J K(-1) mol(-1). The analysis of the vibrational normal modes reveals that for the d(4) systems under study, contrary to Fe(ii) d(6) systems, not all metal-ligand stretching vibrations make a contribution. For the Mn(iii) complex, the only vibration that contributes to DeltaS(vib) involve the nitrogens occupying the Jahn-Teller axis, while in the case of Cr(ii) the contributing vibrations involve the Cr-I bonds. Low-frequency modes due to ring vibrations, metal-ligand bending and movement of the molecule as a whole also contribute to the vibrational entropy associated with the spin transition.
- Affiliations
Citations
Garcia, Y., Paulsen, H., Schünemann, V., Trautwein, A. X., & Wolny, J. A. (2007). Estimate of the vibrational contribution to the entropy change associated with the spin transition in the d4 systems [MnIII(pyrol)3tren] and [CrII(depe)2I2]. Physical chemistry chemical physics : PCCP, 9(10), 1194-1201. https://doi.org/10.1039/b616258d (Original work published 2007)