Iron(II) Spin Crossover Complexes with 4,4′-Dipyridylethyne—Crystal Structures and Spin Crossover with Hysteresis

Dankhoff, Katja; Lochenie, Charles; Weber, Birgit

doi:10.3390/molecules25030581

Cited by 7 publications

(4 citation statements)

References 77 publications

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“…A possible reason for the stepwise spin transition that occurs between 300 and 50 K is the presence of two slightly different iron centers with slightly different chemical surroundings. 77 This idea is supported by the changed magnetic behavior when heating 5 and has been observed before. 55 Alternatively, for similar coordination polymers, the formation of inequivalent iron centers upon spin crossover is observed, leading to alternating HS−LS centers within the chain in the region of the plateau.…”

Section: ■ Introductionsupporting

confidence: 57%

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Iron(II) Spin Crossover Complexes Based on a Redox Active Equatorial Schiff-Base-Like Ligand

et al. 2020

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In this work, two iron(II) coordination compounds with a N 2 O 2 coordinating Schiff base-like ligand bearing a redox active tetrathiafulvalene (TTF) unit and pyridine or trans-1,2-bis(4-pyridylethylene) as an axial ligand are synthesized. Crystals suitable for single X-ray structure analysis were obtained for the new ligand. The complexes were characterized by magnetic susceptibility measurements, T-dependent UV−vis spectroscopy, and cyclic voltammetry. Both complexes display spin transition behavior below room temperature with T 1/2 values of 146 and 156 K. The mononuclear iron(II) complex [Fe TTF L(py) 2 ] is relatively stable up to 400 K compared to similar complexes, showing no loss of axial ligands upon heating. Temperature dependent Mossbauer spectroscopy was conducted for the coordination polymer {[Fe TTF L(bpee)]} n to get more information regarding the origin of the stepwise spin crossover (SCO) behavior observed in the magnetic measurements. The change of the spin state is accompanied by a change of the optical properties, which can be monitored by VT−UV−vis spectroscopy for the mononuclear complex and has been analyzed in theoretical studies. The redox behavior of the iron(II) complexes reveals three reversible redox steps which are located at the iron center and at the TTF unit of the ligand. Oxidation of the TTF unit induces characteristic changes in the UV−vis spectrum that can be followed by spectroelectrochemical UV−vis spectroscopy. Addressing the potential of the ironcentered redox process results in similar changes in the UV−vis spectrum, which indicates an electronic coupling of the redox active unit with the metal center under certain circumstances.

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Section: ■ Introductionsupporting

confidence: 57%

Section: Resultsmentioning

confidence: 79%

Iron(II) Spin Crossover Complexes Based on a Redox Active Equatorial Schiff-Base-Like Ligand

et al. 2020

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“…The net- 7a); that is, in comparison with similar systems, the usual order of complex units in a polymeric strand. [17,[32][33][34] Recently, an ABAB coordination polymer with [Fe(L)] units tilted by 180°was found, having À CF3 groups at the chelate cycle. [35] The FeÀ N ax bond length (ca.…”

Section: Single Crystal X-ray Crystallographymentioning

confidence: 99%

“…2.2 Å) is comparable to similar bond lengths in other reported coordination polymers, [32,36] as is the torsion angle between the pyridyl rings with 20.3°. [33] Considering the molecular packing, the individual onedimensional chains build up to pairs via CÀ H•••π interactions. The array of the chains becomes evident by the highlighted coordination polyhedra shown in the perpendicular view to the bc-plane (Figure 7b).…”

Section: Single Crystal X-ray Crystallographymentioning

confidence: 99%

Sterically Encumbered Coordination Sites. Iron(II) Complexes of Jäger‐type ligands with a Terphenyl Backbone

Dürrmann

Hörner

Wagner

et al. 2021

Zeitschrift anorg allge chemie

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Dedicated to Professor Josef Breu on the Occasion of his 60 th BirthdayA Schiff base-like ligand H 2 L TerPh featuring a para-terphenyl backbone was synthesized and converted in two steps to an octahedral iron(II) coordination polymer with 1,2-bis-(4-pyridyl)ethylene as bridging ligand. Single crystal X-ray structure analysis was possible for the free ligand and the two octahedral iron(II) complexes. The Schiff base-like ligand features a [N 2 O 2 ] 2À coordination sphere for the metal center and the paraterphenyl backbone introduces intrinsic steric constraint. Char-acterization of the coordination polymer with an N 4 O 2 coordination sphere around the iron center via magnetic measurements (SQUID) and room temperature Mössbauer spectroscopy revealed HS character in the entire temperature range investigated. Structure modelling with DFT calculations supports the findings, but support also the possibility of spin crossover in solution.

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Polynuclear Cyanide-Bridged Heterobimetallic Complexes Based-on Pentacyanometallates: Synthesis, Crystal Structure and Magnetic Property

Xin

Xu²,

Meng³

et al. 2022

J Chem Crystallogr

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Iron(II) Spin Crossover Complexes with 4,4′-Dipyridylethyne—Crystal Structures and Spin Crossover with Hysteresis

Cited by 7 publications

References 77 publications

Iron(II) Spin Crossover Complexes Based on a Redox Active Equatorial Schiff-Base-Like Ligand

Iron(II) Spin Crossover Complexes Based on a Redox Active Equatorial Schiff-Base-Like Ligand

Sterically Encumbered Coordination Sites. Iron(II) Complexes of Jäger‐type ligands with a Terphenyl Backbone

Polynuclear Cyanide-Bridged Heterobimetallic Complexes Based-on Pentacyanometallates: Synthesis, Crystal Structure and Magnetic Property

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