title: Vibrational spectrum of the spin crossover complex [Fe(phen)(2)(NCS)(2)] studied by IR and Raman spectroscopy, nuclear inelastic scattering and DFT calculations.
abstract: The vibrational modes of the low-spin and high-spin isomers of the spin crossover complex [Fe(phen)(2)(NCS)(2)] (phen = 1,10-phenanthroline) have been measured by IR and Raman spectroscopy and by nuclear inelastic scattering. The vibrational frequencies and normal modes and the IR and Raman intensities have been calculated by density functional methods. The vibrational entropy difference between the two isomers, DeltaS(vib), which is--together with the electronic entropy difference DeltaS(el)--the driving force for the spin-transition, has been determined from the measured and from the calculated frequencies. The calculated difference (DeltaS(vib) = 57-70 J mol(-1) K(-1), depending on the method) is in qualitative agreement with experimental values (20-36 J mol(-1) K(-1)). Only the low energy vibrational modes (20% of the 147 modes of the free molecule) contribute to the entropy difference and about three quarters of the vibrational entropy difference are due to the 15 modes of the central FeN(6) octahedron.
authors.affiliation: School of Chemistry and Chemical Engineering, Queen's University Belfast, BT9 5AG, Belfast, Northern Ireland.
authors.forename: Kate L
authors.initials: KL
authors.lastname: Ronayne
authors.forename: Hauke
authors.initials: H
authors.lastname: Paulsen
authors.forename: Andreas
authors.initials: A
authors.lastname: Höfer
authors.forename: Andrew C
authors.initials: AC
authors.lastname: Dennis
authors.forename: Juliusz A
authors.initials: JA
authors.lastname: Wolny
authors.forename: Aleksandr I
authors.initials: AI
authors.lastname: Chumakov
authors.forename: Volker
authors.initials: V
authors.lastname: Schünemann
authors.forename: Heiner
authors.initials: H
authors.lastname: Winkler
authors.forename: Hartmut
authors.initials: H
authors.lastname: Spiering
authors.forename: Azzedine
authors.initials: A
authors.lastname: Bousseksou
authors.forename: Philipp
authors.initials: P
authors.lastname: Gütlich
authors.forename: Alfred X
authors.initials: AX
authors.lastname: Trautwein
authors.forename: John J
authors.initials: JJ
authors.lastname: McGarvey
mesh_terms: D005296:Ferrous Compounds / Q000737:chemistry*; D007502:Iron Chelating Agents / Q000737:chemistry*; D007536:Isomerism; D008433:Mathematics; D008958:Models, Molecular; D009584:Nitrogen / Q000737:chemistry; D010618:Phenanthrolines / Q000737:chemistry*; D013055:Spectrophotometry, Infrared / Q000379:methods; D013059:Spectrum Analysis, Raman / Q000379:methods; D013113:Spin Labels; D013816:Thermodynamics
chemical_list: D005296:Ferrous Compounds; D007502:Iron Chelating Agents; D010618:Phenanthrolines; D013113:Spin Labels; D009584:Nitrogen; C025205:1,10-phenanthroline