title: Vibrational properties of the polymeric spin crossover (SCO) Fe(II) complexes [{Fe(4-amino-1,2,4-triazole)3}X2]n: a nuclear inelastic scattering (NIS), Raman and DFT study.
abstract: The vibrational properties of the cationic spin crossover (SCO) coordination polymers [{Fe(4-amino-1,2,4-triazole)(3)}(+2)](n) containing the anions chlorine, methanosulfonate and 1-naphthalenesulfonate have been studied via nuclear inelastic scattering of synchrotron radiation (NIS) as well as by Raman spectroscopy. Although the different anions have a strong influence on the spin crossover temperature, they have little effect on the positions of the spin marker bands in the NIS and Raman spectra. By comparing the line positions of the NIS spin marker bands with those observed by Raman spectroscopy, it has been possible to distinguish vibrations symmetry (A(u) or A(g)) because modes of A(u) and A(g) symmetries are NIS active, but only the A(g) modes are Raman active. The normal mode analysis of charge compensated cationic pentameric and hexameric model structures which have been obtained by density functional calculations reproduces the experimentally observed mode frequencies and the geometry optimization reproduces iron-ligand distances reported for these and related SCO coordination complexes. The effect of charge compensation appears to be independent of the choice of the functional and the basis set which shows that DFT calculations using B3LYP in conjunction with the basis set CEP-31G are a time effective approach in order to study vibrational properties of Fe(II) SCO compounds.
authors.affiliation: Department of Physics, University of Kaiserslautern, D-67663 Kaiserslautern, Germany.
authors.forename: Sergej
authors.initials: S
authors.lastname: Rackwitz
authors.forename: Juliusz A
authors.initials: JA
authors.lastname: Wolny
authors.forename: Kai
authors.initials: K
authors.lastname: Muffler
authors.forename: Klaus
authors.initials: K
authors.lastname: Achterhold
authors.forename: Rudolf
authors.initials: R
authors.lastname: Rüffer
authors.forename: Yann
authors.initials: Y
authors.lastname: Garcia
authors.forename: Rolf
authors.initials: R
authors.lastname: Diller
authors.forename: Volker
authors.initials: V
authors.lastname: Schünemann
mesh_terms: D005296:Ferrous Compounds / Q000737:chemistry*; D008958:Models, Molecular; D011108:Polymers / Q000737:chemistry*; D011789:Quantum Theory; D013059:Spectrum Analysis, Raman; D014732:Vibration
chemical_list: D005296:Ferrous Compounds; D011108:Polymers