One Shot Laser Pulse Induced Reversible Spin Transition in the Spin-Crossover Complex [Fe(C4H4N2){Pt(CN)4}] at Room Temperature

The [Fe(PM-BiA)2(NCS)2] complex, where PM is N-2-pyridylmethylene and BiA is 4-aminobiphenyl, crystallizes in two polymorphs. The two phases, denoted (I) and (II), undergo a spin-crossover when the sample is cooled and present distinct spin-transition features as (I) shows a very abrupt spin transition, while (II) exhibits a gradual transition. The two forms of the complex are used to investigate the correlations that exist between the spin-transition features and structural features. This article presents the crystal structures of polymorph (II) at room temperature (high spin) and at 120 K (low spin), including a comparison with those of polymorph (I). This study reveals that the packing, in a first approximation, is similar in both forms. In order to look at the crystal structures in more detail, a new angular parameter, denoted θNCS, as well as a particular type of intermolecular hydrogen-bond interaction, which involves the S atoms of the NCS ligands, are investigated. Interestingly, this angle and this intermolecular interaction can be directly connected to the cooperativity of the spin transition. Such a result is extended to all the SCO iron(II) complexes belonging to the same family of the general formula [Fe(PM-L)2(NCS)2].

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Five 2,6-Di(pyrazol-1-yl)pyridine-4-carboxylate Esters, and the Spin States of their Iron(II) Complexes

Magnetochemistry ◽

10.3390/magnetochemistry5010009 ◽

2019 ◽

Vol 5 (1) ◽

pp. 9 ◽

Cited By ~ 1

Author(s):

Iurii Galadzhun ◽

Rafal Kulmaczewski ◽

and Malcolm A. Halcrow

Keyword(s):

Room Temperature ◽

Spin Crossover ◽

Thermal Hysteresis ◽

Spin Transition ◽

Benzyl Ester ◽

The Other ◽

Spin States ◽

Phenyl Ester ◽

Coupling Reagent ◽

Complex Salts

Two phenyl ester and three benzyl ester derivatives have been synthesized from 2,6-di(pyrazol-1-yl)pyridine-4-carboxylic acid and the appropriate phenyl or benzyl alcohol using N,N’-dicyclohexylcarbodiimide as the coupling reagent. Complexation of the ligands with Fe[BF4]2·6H2O in acetone yielded the corresponding [FeL2][BF4]2 complex salts. Four of the new ligands and four of the complexes have been crystallographically characterised. Particularly noteworthy are two polymorphs of [Fe(L3)2][BF4]2·2MeNO2 (L3 = 3,4-dimethoxyphenyl 2,6-di{pyrazol-1-yl}pyridine-4-carboxylate), one of which is crystallographically characterised as high-spin while the other exhibits the onset of spin-crossover above room temperature. The other complexes are similarly low-spin at low temperature but exhibit gradual spin-crossover on heating, except for an acetone solvate of [Fe(L5)2][BF4]2 (L5 = benzyl 2,6-di{pyrazol-1-yl}pyridine-4-carboxylate), which exhibits a more abrupt spin-transition at T½ = 273 K with 9 K thermal hysteresis.

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Two New Iron(II) Spin-Crossover Complexes with N4O2Coordination Sphere and Spin Transition around Room Temperature

European Journal of Inorganic Chemistry ◽

10.1002/ejic.200900846 ◽

2009 ◽

Vol 2009 (36) ◽

pp. 5527-5534 ◽

Cited By ~ 26

Author(s):

Birgit Weber ◽

Jaroslava Obel ◽

Dunie Henner-Vásquez ◽

Wolfgang Bauer

Keyword(s):

Room Temperature ◽

Spin Crossover ◽

Spin Transition ◽

Spin Crossover Complexes

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High-temperature Spin Crossover of a Solvent-Free Iron(II) Complex with the Linear Hexadentate Ligand [Fe(L2-3-2Ph)](AsF6)2 (L2-3-2Ph = bis[N-(1-Phenyl-1H-1,2,3-triazol-4-yl)methylidene-2-aminoethyl]-1,3- propanediamine)

Magnetochemistry ◽

10.3390/magnetochemistry5010010 ◽

2019 ◽

Vol 5 (1) ◽

pp. 10 ◽

Cited By ~ 2

Author(s):

Hiroaki Hagiwara

Keyword(s):

Room Temperature ◽

Spin Crossover ◽

Variable Temperature ◽

Spin Transition ◽

Three Dimensional ◽

Solvent Free ◽

Supramolecular Network ◽

Scanning Calorimetry ◽

Mononuclear Iron ◽

3D Network

A novel mononuclear iron(II) complex with a linear hexadentate N6 ligand, containing two 1,2,3-triazole moieties, [Fe(L2-3-2Ph)](AsF6)2 (1), was synthesized (L2-3-2Ph = bis[N-(1-Phenyl-1H-1,2,3-triazol-4-yl)methylidene-2-aminoethyl]-1,3-propanediamine). Variable-temperature magnetic susceptibility measurements revealed a gradual one-step spin crossover (SCO) between the high-spin (HS, S = 2) and low-spin (LS, S = 0) states above room temperature (T1/2 = 468 K). The spin transition was further confirmed by differential scanning calorimetry (DSC). A single-crystal X-ray diffraction study showed that the complex was in the LS state (S = 0) at room temperature (296 K). In the crystal lattice, a three-dimensional (3D) supramolecular network was formed by intermolecular CH⋯ and – interactions of neighboring complex cations [Fe(L2-3-2Ph)]2+. AsF6− ions were located interstitially in the 3D network of complex cations, with no solvent-accessible voids. The crystal structure at 448 K (mixture of HS and LS species) was also successfully determined thanks to the thermal stability of the solvent-free crystal.

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