Document type
ArticleVersion
Accepted versionPublication date
All rights reserved
Please use this identifier to cite or link to this item: https://hdl.handle.net/2445/153539
A spin-crossover molecular material describing four distinct thermal pathways
Journal Title
Director/Tutor
Journal ISSN
Volume Title
Related resource
Abstract
Spin-crossover (SCO) molecular solids are valued switchable materials for their common abrupt and reversible thermal transitions, large thermal hysteresis, or guest-dependent effects. These properties usually involve crystallographic transitions coupled to the SCO events. These phenomena are of great value for the understanding of solidstate transformations and also for exploiting them. We present here a lattice of the complex [FeL(bbp)](ClO4)2 (1; L and bbp are tris-imine ligands) featuring an unprecedented rich succession of SCO and crystallographic phase transformations. Magnetometry measurements unveil a thermally irreversible sequence of spin conversions that delineate four different thermal pathways. All of these are single-crystal-tosingle- crystal processes and can thus be monitored by single crystal X-ray diffraction using one unique specimen. Fresh crystals of 1 contain one molecule of acetone per Fe center (1·ac) that abandons the lattice upon warming at the same time that a SCO from an ordered mixed spin state (1:1 high spin/low spin; HS/LS) to a fully HS state, 1α, occurs. This crystallographic phase, accessed through a template effect by the solvent, converts into another one, 1β, upon cooling, as triggered by a HS to LS SCO. Warming of 1β induces a new SCO (LS to ordered HS/LS) coupled to another crystallographic phase transition, 1β → 1γ. The fully HS state of 1γ can not be reached before decomposition of the compound. Instead, this phase cycles between the HS/LS and the LS states through superimposable pathways, different from that of the prerequired 1β → 1γ phase change. Analysis of the thermal variation of the free energy, G, through density functional theory methods provides trends in agreement with the observation of these transformations and clarifies the possible metastable nature of the various phases identified. This unique behavior allows the access to four different magnetic responses depending on the thermal history of the sample, within a given range of temperatures near the ambient conditions.
Subject (English)
Citation
Citation
BARTUAL-MURGUI, Carlos, et al. A spin-crossover molecular material describing four distinct thermal pathways. Inorganic Chemistry. 2018. Vol. 57, num. 17, pags. 11019-11026. ISSN 0020-1669. [consulted: 18 of June of 2026]. Available at: https://hdl.handle.net/2445/153539