The number and shape of lattice solvent molecules controls spin-crossover in an isomorphous series of crystalline solvate salts

Izar Capel Berdiell; Rafal Kulmaczewski; Namrah Shahid; Oscar Cespedes; Malcolm A Halcrow

doi:10.1039/d1cc02624k

The number and shape of lattice solvent molecules controls spin-crossover in an isomorphous series of crystalline solvate salts

Chem Commun (Camb). 2021 Jul 1;57(53):6566-6569. doi: 10.1039/d1cc02624k.

Authors

Izar Capel Berdiell¹, Rafal Kulmaczewski², Namrah Shahid², Oscar Cespedes³, Malcolm A Halcrow²

Affiliations

¹ School of Chemistry, University of Leeds, Woodhouse Lane, Leeds LS2 9JT, UK. m.a.halcrow@leeds.ac.uk and Institute of Electronic Structure and Laser, Foundation for Research and Technology-Hellas, P.O. Box 1527, Heraklion GR-711 10, Greece.
² School of Chemistry, University of Leeds, Woodhouse Lane, Leeds LS2 9JT, UK. m.a.halcrow@leeds.ac.uk.
³ School of Physics and Astronomy, University of Leeds, EC Stoner Building, Leeds LS2 9JT, UK.

PMID: 34113938
DOI: 10.1039/d1cc02624k

Abstract

Crystals of [FeL2][BF4]2·nMeCN (L = N-(2,6-di{pyrazol-1-yl}pyrid-4-yl)acetamide; n = 1 or 2) and [FeL2][ClO4]2·MeCN are isomorphous. When n = 1 the compounds exhibit an abrupt, hysteretic spin-transition below 200 K, but when n = 2 the material remains high-spin on cooling. [FeL2]X2·EtCN (X- = BF4- or ClO4-) are isomorphous with the MeCN solvates and undergo their spin-transition at almost the same temperature. However this now occurs in two-steps via a re-entrant mixed-spin intermediate phase, which correlates with crystallographic ordering of the bent propionitrile molecule.