Abstract
AbstractA Schiff base‐like ligand bearing a maleonitrile backbone was synthesized and converted in two steps to an octahedral iron(II) complex with axial imidazole ligands. Single crystal X‐ray structure analysis of this complex revealed a 3D hydrogen bond network based on the NH groups of the axial imidazole ligands that act as donors. Interestingly, temperature‐dependent magnetic measurements showed an abrupt spin crossover with hysteresis above room temperature. Thereby, the hysteresis width features a strong scan rate dependency leading to a 6 K wide hysteresis at a scan rate of 5 K/min and 1 K width when measured in settle mode. This kinetic effect is further investigated by DSC measurements verifying the strong scan rate dependency of the hysteresis width. The small hysteresis was additionally followed using temperature‐dependent PXRD. For comparison, the corresponding pyridine complex was synthesized as well.
Highlights
A Schiff base-like ligand bearing a maleonitrile backbone was synthesized and converted in two steps to an octahedral iron(II)
Single crystal X-ray structure analysis of this complex revealed a 3D hydrogen bond network based on the NH groups of the axial imidazole ligands that act as donors
Cooperative effects are associated with intermolecular interactions, which can either be based on long-range interactions as found in 1D coordination polymers,[5,6,7] or on short-range interactions such as π-π stacking[8] or a hydrogen bond network.[9]
Summary
Schiff base-like Ligand and Scan Rate-dependent Hysteresis above Room Temperature. Dedicated to Professor Peter Klüfers on the Occasion of his 70th Birthday. Cooperative effects are associated with intermolecular interactions, which can either be based on long-range interactions as found in 1D coordination polymers,[5,6,7] or on short-range interactions such as π-π stacking[8] or a hydrogen bond network.[9] In 2008 Weber et al reported studies on a mononuclear octahedral iron(II) complex with a Schiff base-like equatorial ligand and imidazole as axial ligands that showed an abrupt spin crossover around room temperature with a 70 K wide thermal hysteresis.[10,11] Crystal structure analysis of this. In 2011 Garcia et al studied the magnetic behavior of this interesting complex in detail Thereby, they reported a polymorph, which showed an abrupt SCO with a 5 K width hysteresis above room temperature.[9] Interestingly, a comparison of the crystal structures of these two polymorphs revealed that in both cases a hydrogen bond network is formed.
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