Spin crossover, polymorphism and porosity to liquid solvent in heteroleptic iron(III) {quinolylsalicylaldimine/thiosemicarbazone-salicylaldimine} complexes

Wasinee Phonsri, Casey G Davies, Guy N L Jameson, Boujemaa Moubaraki, Keith Spencer Murray

Research output: Contribution to journalArticleResearchpeer-review

23 Citations (Scopus)

Abstract

Heteroleptic iron(III) complexes of formula [Fe(qsal)(thsa)]solvent have been synthesized: [Fe(qsal)(thsa)]0.4 BuOH (1), [Fe(qsal)(thsa)]0.5 MeCN (2) and [Fe(qsal)(thsa)]0.5 THF, (3). The latter two show partial solvent loss at room temperature to yield [Fe(qsal)(thsa)]0.1 MeCN (2′) and [Fe(qsal)(thsa)]0.1 THF (3′), respectively. This family maintains a structural integrity which is analogous over different degrees of solvation, a rare occurrence in discrete molecular species. Uniquely, removal of MeCN from compound 2 leads to retention of crystallinity yielding the isostructural, fully desolvated compound [Fe(qsal)(thsa)] (2′′) and a new high spin polymorph, 4. To the best of our knowledge, this is the first compound that forms polymorphs through a desolvation process. The desolvated mixture, 2′′ and 4, is porous and can reabsorb MeCN and give rise to 2′ again. This illustrates the reversible single-crystal-to-single-crystal transformation of two polymorphs back to a purely original phase, 2′′+4↔2′. The structural, magnetic and Mossbauer features of the various samples are described in terms of spin crossover. Sign of the cross: [Fe(qsal)(thsa)]solvent complexes, where solvent is MeCN or THF, have been characterized. For MeCN compounds, spin crossover properties are observed in both the solvated and non-solvated compounds (see scheme). Interestingly, the desolvation process in [Fe(qsal)(thsa)]n MeCN resulted in two new polymorphs of FeIII spin crossover systems, for the first time. The desolvated material is porous to liquid MeCN.
Original languageEnglish
Pages (from-to)1322-1333
Number of pages12
JournalChemistry - A European Journal
Volume22
Issue number4
DOIs
Publication statusPublished - 2016

Keywords

  • heteroleptic ligands
  • iron(III) spin crossover
  • polymorphs
  • porosity
  • solvent effects

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