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Thermal and Optical Switching of Molecular Spin States in the {[FeL[H2B(pz)2]2} Spin-Crossover System (L= bpy, phen)

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Thermal and Optical Switching of Molecular Spin States in the {[FeL[H2B(pz)2]2} Spin-Crossover System (L= bpy, phen)

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dc.contributor.author Moliner, Nicolás es_ES
dc.contributor.author Salmon, Lionel es_ES
dc.contributor.author Capes, Laurence es_ES
dc.contributor.author Muñoz Roca, María Del Carmen es_ES
dc.contributor.author Létard, Jean-François es_ES
dc.contributor.author Bousseksou, Azzedine es_ES
dc.contributor.author Tuchagues, Jean-Pierre es_ES
dc.contributor.author McGarvey, John J. es_ES
dc.contributor.author Dennis, Andrew C. es_ES
dc.contributor.author Castro, Miguel es_ES
dc.contributor.author Burriel, Ramón es_ES
dc.contributor.author Real, José Antonio es_ES
dc.date.accessioned 2020-10-15T03:31:43Z
dc.date.available 2020-10-15T03:31:43Z
dc.date.issued 2002-04-25 es_ES
dc.identifier.issn 1520-6106 es_ES
dc.identifier.uri http://hdl.handle.net/10251/151884
dc.description.abstract [EN] Mössbauer and Raman spectroscopies, calorimetric measurements, the LIESST effect (light induced excited spin state trapping) and dynamics of the high-spin (HS) to low-spin (LS) relaxation have been investigated in order to thoroughly study the spin-crossover compounds of formula {Fe(L)[H2B(pz)2]2}, where L = 2,2`-bipyridine (1) and 1,10-phenanthroline (2). The Mössbauer studies have revealed the occurrence of an almost complete spin conversion at low temperature, while 9.5% (1) and 15% (2) of molecules remain LS at room temperature. The thermal variation of the proportion of HS molecules, nHS, obtained from the Mössbauer spectra has been used to calibrate the thermal dependence of nHS deduced from the magnetic susceptibility measurements. The thermodynamic Slichter and Drickamer model was used to fit the thermal variation of nHS. The estimated thermodynamic parameters are ¿H = 7.7 kJ mol-1, ¿S = 47.4 J mol-1 K-1 and interaction parameter ¿ = 2.1 kJ mol-1 for 1 and ¿H = 7.9 kJ mol-1, ¿S = 48.3 J mol-1 K-1 and ¿ = 3 kJ mol-1 for 2. These data agree with those obtained from heat capacity experiments:¿ ¿H = 7.7 ± 0.4 kJ mol-1 and ¿S = 48 ± 3 J mol-1 K-1 for 1, and ¿H = 8.0 ± 0.4 kJ mol-1 and ¿S = 49 ± 3 J mol-1 K-1 for 2. The transition temperatures, estimated from the heat capacity peaks, were Tc = 159.5 K for 1, and Tc(up) = 165.0 K, Tc(down) = 162.7 K for 2, in heating and cooling processes. Raman spectra have been recorded for 2 both in the HS (300 K) and LS (110 K) states. Significant changes occur in the position of several low-frequency Raman modes in the low-temperature spectrum. The entropy change associated with the 15 normal vibrational modes of the [FeN6] pseudo-octahedron has been estimated from the measured spectra as ¿Svib = 36 J K-1 mol-1, and the total entropy change is ¿S = ¿Svib + ¿Sel = 49 J K-1 mol-1. This value is comparable to that obtained from the calorimetric measurements. Photomagnetic studies revealed a complete conversion from the LS into the HS state upon irradiation at 10 K in the 647.1¿676.4 nm wavelength region. The critical LIESST temperatures are 52 K (1) and 44 K (2). The dynamics of the LS to HS conversion was studied for the two compounds in the 6¿50 K temperature range. In the thermally activated region the apparent activation energy, Ea, was estimated to be 240 cm-1 for 1 and 170 cm-1 for 2. In the tunneling region the rate constants were estimated to lie in the 9 × 10-7 to 1 × 10-6 s-1 range. es_ES
dc.description.sponsorship We deeply thank Professor François Varret for very helpful discussions. We are grateful to the European Commision for financial support through the TMR-Network "Thermal and Optical Switching of Spin States (TOSS)", Contract No. ERB-FMRX-CT98-0199EEC/TMR. We thank the financial assistance from the Spanish DGICYT through Projects PB97-1397 and MAT97-0987, and the Programa de AccionesIntegradas Hispano-Francesas (HF1999-0091) es_ES
dc.language Inglés es_ES
dc.publisher American Chemical Society es_ES
dc.relation EC/ERB-FMRX-CT98-0199EEC/TMR es_ES
dc.relation DGICYT/PB97-1397 es_ES
dc.relation DGICYT/MAT97-0987 es_ES
dc.relation.ispartof The Journal of Physical Chemistry B es_ES
dc.rights Reserva de todos los derechos es_ES
dc.subject.classification FISICA APLICADA es_ES
dc.title Thermal and Optical Switching of Molecular Spin States in the {[FeL[H2B(pz)2]2} Spin-Crossover System (L= bpy, phen) es_ES
dc.type Artículo es_ES
dc.identifier.doi 10.1021/jp013872b es_ES
dc.rights.accessRights Cerrado es_ES
dc.contributor.affiliation Universitat Politècnica de València. Departamento de Física Aplicada - Departament de Física Aplicada es_ES
dc.description.bibliographicCitation Moliner, N.; Salmon, L.; Capes, L.; Muñoz Roca, MDC.; Létard, J.; Bousseksou, A.; Tuchagues, J.... (2002). Thermal and Optical Switching of Molecular Spin States in the {[FeL[H2B(pz)2]2} Spin-Crossover System (L= bpy, phen). The Journal of Physical Chemistry B. 106(16):4276-4283. https://doi.org/10.1021/jp013872b es_ES
dc.description.accrualMethod S es_ES
dc.relation.publisherversion https://doi.org/10.1021/jp013872b es_ES
dc.description.upvformatpinicio 4276 es_ES
dc.description.upvformatpfin 4283 es_ES
dc.type.version info:eu-repo/semantics/publishedVersion es_ES
dc.description.volume 106 es_ES
dc.description.issue 16 es_ES
dc.relation.pasarela S\21789 es_ES
dc.contributor.funder European Commission es_ES
dc.contributor.funder Dirección General de Investigación Científica y Técnica es_ES


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