Thiazolylimines as novel ligand-systems for spin-crossover centred near room temperature

Abstract

A new thiazolylimine ligand system for iron(ii) complexes which stabilises spin-crossover in solution and solid states with T1/2 temperatures around room temperature has been developed. This effect is studied in solution and solid states. Furthermore crystal packing effects are investigated offering a variety of T1/2 and even hysteresis centred at -3 °C in the solid state.

Stepwise Construction of Heterobimetallic Cages by an Extended Molecular Library Approach

“…Covalently bridged and preorganized binding sites dictate the fac coordination of the cation. The crystals occur in racemic form because both Λ- and Δ-configured complexes are present in the unit cell, as was already observed with analogous TREN-based mononuclear iron­(II) complexes …”

“…The synthesis of ML turned out to be quite simple, which could already be shown in analogous subcomponent self-assembly reactions of mononuclear iron­(II) complexes . The reaction of 3 equiv of the aldehyde building block 1 with 1 equiv of 2 and iron­(II) tetrafluoroborate hexahydrate yielded the deep-violet metalloligand [ ML ]­(BF 4 ) 2 in 86% yield (Scheme ).…”

Cation modulated spin state and near room temperature transition within a family of compounds containing the same [FeL2]2− center

“…This suggests that a complete and abrupt spin conversion from the HS to LS state is achieved at a T 1/2 cooling of 278 K. Heating the sample leads to another abrupt spin conversion at 286 K ( T 1/2 warming ), giving a narrow thermal hysteresis loop of 8 K, centered ( T c ) at 282 K (9 °C). It should be pointed out that 3 belongs to one of the very particular SCO complexes that show a very abrupt spin transition with the hysteresis loop near the RT region, 15,16,18–22,64–66 which makes it an excellent candidate for molecular switches and memory devices in practical applications.…”

Eine Familie von Heterobimetallischen Würfeln zeigt Spin‐Crossover‐Verhalten nahe Raumtemperatur

“…Dieses Resultat stimmt somit auch mit den Ergebnissen anderer Studien überein, die den Einfluss verschiedener Azol‐Bausteine auf das Spin‐Crossover‐Verhalten von Eisen(II)‐Kationen untersuchten. Dabei wiesen Thiazole regelmäßig das stärkste Ligandenfeld unter den Azolen auf und führten folglich zu den höchsten Spin‐Übergangstemperaturen [10e, 16b,c, 19] …”

“…Aus der Literatur ist bekannt, dass der Austausch von Azin‐Bausteinen im letzten Teilschritt der Selbstorganisation durch geeignete Azol‐Bausteine eine effektive Möglichkeit darstellt, die Ligandenfeldstärke zu verringern. Eine solche Verringerung der Ligandenfeldstärke kann letztlich zur Stabilisierung des paramagnetischen high‐spin ‐Zustandes in Eisen(II)‐Kationen führen und bei geschickter Feinabstimmung sogar einen Spin‐Crossover‐Prozess ermöglichen [10d,e, 16, 17a,b, 18, 19] …”