We report the unprecedented observation of reversible interface propagation in the switchable cooperative Fe(Ⅲ)spin crossover compound[Fe(3-EtO-salEen)_(2)]NO_(3),where 3-EtO-salEen is 3-ethoxy-N-ethyl-N-(2-aminoethy...We report the unprecedented observation of reversible interface propagation in the switchable cooperative Fe(Ⅲ)spin crossover compound[Fe(3-EtO-salEen)_(2)]NO_(3),where 3-EtO-salEen is 3-ethoxy-N-ethyl-N-(2-aminoethyl)salicylaldiminate.This complex exhibits a spin transition from low-spin to high-spin states,triggered by temperature around 345 K.Magnetic susceptibility measurements reveal an abrupt transition with a thermal hysteresis of 5 K.Differential scanning calorimetry confirms both endothermic(T_(on)=344.50 K and T_(max)=345.61 K,Δ_(trs)H°_(m)=12:05 kJ mol^(-1)andΔ_(trs)S°_(m)=34:98 J mol^(-1))and exothermic(T_(on)=344.40 K,T_(max)=345.49 K,Δ_(trs)H°_(m)=10:98 kJ mol^(-1)andΔ_(trs)S°_(m)=31:88 J mol^(-1))peaks corresponding to the spin transition temperatures.Cryogenic optical microscopy reveals rapid interface propagation,with velocities(v_(HS→LS)≃1672μm s^(−1)and v_(LS→HS)≃850μm s^(−1))significantly higher than those observed in traditional Fe(II)-based spin crossover materials.The high-speed propagation is attributed to the combined effect of the reduced volume change and lower elastic energy barriers associated with the transition in Fe(Ⅲ)systems and the high values of the transition temperatures.Hirshfeld surface analysis reveals that the cooperative nature of the transition is influenced by non-conventional hydrogen bonding andπ-πinteractions.This study represents the first report of reversible interface propagation in Fe(Ⅲ)complexes,providing valuable insights into the fundamental mechanisms that govern spin crossover transitions in these systems.展开更多
基金Centro de Química Estrutural(CQE)and Institute of Molecular Sciences(IMS)acknowledge the financial support of Fundação para a Ciência e Tecnologia(FCT),projects UID/00100/2025,UID/PRR/100/2025LA/P/0056/2020(https://doi.org/10.54499/LA/P/0056/2020),respectively+6 种基金Centro de Física Teórica e Computacional(CFTC)acknowledges FCT under contracts no.UIDB/00618/2020(https://doi.org/10.54499/UIDB/00618/2020)and UIDP/00618/2020(https://doi.org/10.54499/UIDP/00618/2020).PN Martinho thanks FCT for grant PTDCQUI-QIN0252_2021(https://doi.org/10.54499/PTDC/QUI-QIN/0252/2021)for contract 2023.15441.TENURE.003/CP00003/CT00011 and the co-financing by the PRR-Recovery and Resilience Plan of the European UnionThis research was partly funded by ANR(Agence Nationale de la Recherche Scientifique),grant number Mol-CoSM ANR-20-CE07-0028-0CNRS through the MITI interdisciplinary programs through its exploratory research program.The authors acknowledge financial support from the Spanish Ministerio de Ciencia e Innovación through grants MCIN/AEI/10.13039/501100011033 PID2021-126076NB-I00 and TED2021-129506B-C22,funded partially by FEDER Una manera de hacer Europa,the unit of excellence María de Maeztu CEX2021-001202-M granted to the IQTCUB,the COST Action CA18234the Generalitat de Catalunya 2021SGR00079 grantF.V.thanks the ICREA Academia Award 2023 Ref.Ac2216561COST Actions CA21101(COSY)and CA22131(LUCES)are also acknowledged.
文摘We report the unprecedented observation of reversible interface propagation in the switchable cooperative Fe(Ⅲ)spin crossover compound[Fe(3-EtO-salEen)_(2)]NO_(3),where 3-EtO-salEen is 3-ethoxy-N-ethyl-N-(2-aminoethyl)salicylaldiminate.This complex exhibits a spin transition from low-spin to high-spin states,triggered by temperature around 345 K.Magnetic susceptibility measurements reveal an abrupt transition with a thermal hysteresis of 5 K.Differential scanning calorimetry confirms both endothermic(T_(on)=344.50 K and T_(max)=345.61 K,Δ_(trs)H°_(m)=12:05 kJ mol^(-1)andΔ_(trs)S°_(m)=34:98 J mol^(-1))and exothermic(T_(on)=344.40 K,T_(max)=345.49 K,Δ_(trs)H°_(m)=10:98 kJ mol^(-1)andΔ_(trs)S°_(m)=31:88 J mol^(-1))peaks corresponding to the spin transition temperatures.Cryogenic optical microscopy reveals rapid interface propagation,with velocities(v_(HS→LS)≃1672μm s^(−1)and v_(LS→HS)≃850μm s^(−1))significantly higher than those observed in traditional Fe(II)-based spin crossover materials.The high-speed propagation is attributed to the combined effect of the reduced volume change and lower elastic energy barriers associated with the transition in Fe(Ⅲ)systems and the high values of the transition temperatures.Hirshfeld surface analysis reveals that the cooperative nature of the transition is influenced by non-conventional hydrogen bonding andπ-πinteractions.This study represents the first report of reversible interface propagation in Fe(Ⅲ)complexes,providing valuable insights into the fundamental mechanisms that govern spin crossover transitions in these systems.
