A team of researchers have synthesised an iron(II) bispyrazolylpyridine complex in order to elucidate the interplay between spin transition and polymorphism.
Complexes demonstrating high spin–low spin crossover could prove to be very useful materials in technologies which rely on switching mechanisms, however, to use them to their full potential, any properties affecting their performance need to be understood – crystal symmetry being one of them. Mario Ruben and co-workers discovered that crystallisation of the iron(II) bispyrazolylpyridine complex produced two polymorphs which upon heating, yields a third polymorphic form. Interestingly, the different polymorphs each demonstrate different magnetic behaviour.
Whilst one polymorph, exhibits an abrupt, hysteretic high/low spin transition, the other remains low spin. The team have attributed this to varying levels of inter-molecular cooperativity within the crystal structures.
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The interplay of iron(II) spin transition and polymorphism
Ivan Šalitroš, Olaf Fuhr, Andreas Eichhöfer, Robert Kruk, Ján Pavlik, Lubor Dlháň, Roman Boča and Mario Ruben