First Cobalt(II) Spin Crossover Compound with N4S2-Donorset.

Fabian Fürmeyer,Eva Rentschler,Luca M Carrella,Danny Münzberg

doi:10.3390/molecules25040855

Fabian Fürmeyer, Eva Rentschler + Show 2 more

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https://doi.org/10.3390/molecules25040855

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Abstract

Herein we report the synthesis and characterization of a novel bis-tridentate 1,3,4-thiadiazole ligand (L = 2,5-bis[(2-pyridylmethyl)thio]methyl-1,3,4-thiadiazole). Two new mononuclear complexes of the type [MII(L)2](ClO4)2 (with M = FeII (C1) and CoII (C2)) have been synthesized, containing the new ligand (L). In both complexes the metal centers are coordinated by an N4S2-donorset and each of the two ligands is donating to the metal ion with just one of the tridentate pockets. The iron(II) complex (C1) is in the low spin [LS] state below room temperature and shows an increase in the magnetic moment only above 300 K. In contrast, the cobalt(II) complex (C2) shows a gradual spin crossover (SCO) with T1/2 = 175 K. To our knowledge, this is the first cobalt(II) SCO complex with an N4S2-coordination.

Highlights

Switching metal complexes between two different electronic states, high spin [HS] and low spin [LS], by external stimuli such as temperature, light irradiation or pressure is known as spin crossover (SCO)
Abruptness of the property changes and the occurrence of a thermal hysteresis is necessary for future applications
Both depend on the cooperative interactions between the metal centers in the solid state

Summary

Introduction

Switching metal complexes between two different electronic states, high spin [HS] and low spin [LS], by external stimuli such as temperature, light irradiation or pressure is known as spin crossover (SCO). Abruptness of the property changes and the occurrence of a thermal hysteresis is necessary for future applications. Both depend on the cooperative interactions between the metal centers in the solid state. ‘Intermolecularly’, the cooperativity can be enhanced by hydrogen bonding or π-π-stacking interactions between the complexes. SCO coordination polymers often show large thermal hysteresis [14,15], research on discrete polynuclear, and in particular in dinuclear SCO systems recently increased because the latter have better reproducibility and easier characterization. The dimeric structural motif as the simplest and smallest model for investigating intramolecular cooperative interactions offers potential access to three states

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