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Interplay of Spin Conversion and Structural Phase Transformations: Re‐Entrant Phase Transitions in the 2‐Propanol Solvate of Tris(2‐picolylamine)iron(II) Dichloride
Author(s) -
Törnroos Karl W.,
Hostettler Marc,
Chernyshov Dmitry,
Vangdal Brita,
Bürgi HansBeat
Publication year - 2006
Publication title -
chemistry – a european journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.687
H-Index - 242
eISSN - 1521-3765
pISSN - 0947-6539
DOI - 10.1002/chem.200600547
Subject(s) - spin crossover , chemistry , intermolecular force , atmospheric temperature range , phase (matter) , solvent , molecule , crystallography , hysteresis , crystal (programming language) , phase transition , spin (aerodynamics) , thermodynamics , condensed matter physics , organic chemistry , physics , computer science , programming language
Crystal structures, magnetic and thermodynamic properties of the spin‐crossover compound tris(2‐picolylamine)iron(II) dichloride (with 2‐propanol solvent molecules) have been measured in the temperature range from 15 to 293 K. X‐ray diffraction, SQUID, and calorimetric experiments all showed two first‐order phase transitions with hysteresis loops, a narrow one at T 1 ∼196 K and a broad, triangular one covering the range 153< T 2 <166 K. Crystal structures were analysed at fourteen temperatures in a cooling cycle and at seven temperatures in a heating cycle. They reveal a complex, temperature‐dependent ordering behaviour of both the complex cations and the alcohol molecules. A phenomenological model accounting for spin conversion, solvent ordering and coupling between the two processes describes the observed phase transitions and ordering phenomena reasonably well. Similarities and differences in the behaviour of the corresponding ethanol solvate with the same crystal architecture are discussed. It is concluded that spin‐crossover behaviour depends as much on molecular properties as it does on intermolecular interactions, both of the spin active and the spin inactive components.