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Comptes Rendus Chimie
Volume 8, n° 8
pages 1317-1325 (août 2005)
Doi : 10.1016/j.crci.2004.11.032
Received : 29 June 2004 ;  accepted : 25 November 2004
Isotope effects on the vibrational spectra of the Fe(Phen)2 (NCS)2 spin-crossover complex studied by density functional calculations

Villő K. Pálfi a, b, Thomas Guillon a, Hauke Paulsen c, Gábor Molnár a, Azzedine Bousseksou a,
a Laboratoire de chimie de coordination, UPR 8241 CNRS, 205, route de Narbonne, 31077 Toulouse cedex, France 
b Institut of Chemistry, Eötvös Loránd University, Pázmány P. s. 1/A, H-1117 Budapest, Hungary 
c Institute of Physics, University of Luebeck, Ratzeburger Allee 160, 23538 Luebeck, Germany 

*Corresponding author.

A geometry optimization and vibrational frequency calculation has been carried out on the Fe(phen)2 (NCS)2 (phen= 1,10 phenantroline) molecule in both spin states (S = 0 and S = 2) using the density functional theory (DFT) method with the B3LYP functional and the 6-31G(d) basis set. The frequency shifts upon 54Fe-57Fe and 14N-15N isotope substitutions have been calculated and compared with the experimental frequency shifts as well as with calculated data (DFT/BP86) published in the literature. In the low frequency region (100-600 cm-1), both DFT methods reproduce correctly the measured isotope shifts. The accuracy of the calculated vibrational entropy change upon the spin crossover (SCO) is lower: reasonable errors (~10%) of the calculated frequencies lead to a relatively large error (~50%) of the total entropy change. To cite this article: V.K. Pálfi et al., C. R. Chimie 8 (2005) .

The full text of this article is available in PDF format.

Des études d'optimisation de géométrie et des calculs de fréquences vibrationnelles ont été effectués sur la molécule Fe(phen)2 (NCS)2 (phen= 1,10 phenantroline) dans les deux états de spins (S = 0 et S = 2) à l'aide de la théorie de la fonctionnelle densité (DFT). Les fonctionnelles B3LYP et base 6-31G(d) ont été choisies. Les déplacements fréquentiels lors des substitutions isotopiques 54Fe-57Fe puis 14N-15N ont été calculés et comparés avec les déplacements obtenus expérimentalement et ainsi à ceux obtenus dans la littérature par la fonctionnelle BP86, déjà publiés. Dans la région des basses fréquences (100-600 cm-1), les deux méthodes de calcul reproduisent correctement les déplacements isotopiques expérimentaux. L'erreur sur le calcul de la variation d'entropie est cependant importante : une erreur de 10% sur les fréquences de vibration induit une erreur de 50% sur la variation totale d'entropie. Pour citer cet article : V.K. Pálfi et al., C. R. Chimie 8 (2005) .

The full text of this article is available in PDF format.

Keywords : DFT, Spin crossover, Vibrational frequencies, Isotope effect, Vibrational entropy

Mots clés : DFT, Transition de spin, Fréquences vibrationnelles, Effet isotopique, Entropie vibrationnelle

© 2005  Académie des sciences@@#104156@@
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