Halogen Substituent Effect on the Spin-Transition Temperature in Spin-Crossover Fe(III) Compounds Bearing Salicylaldehyde 2-Pyridyl Hydrazone-Type Ligands and Dicarboxylic Acids

Nakanishi, Takumi; Okazawa, Atsushi; Sato, Osamu

doi:10.3390/inorganics5030053

Cited by 11 publications

(9 citation statements)

References 32 publications

(30 reference statements)

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“…The additional presence of hydrogen bonding and cation-π interactions allow the 2D network structure to accommodate the geometric changes around the metal during SCO. Sato et al described the synthesis [88] of four Fe(III) SCO compounds [Fe(L9) 2 ] + , with salicylaldehyde 2-pyridyl hydrazone-type ligands (L9, X = Cl, Br) and dicarboxylic acid monoanions (tetrachloroterephtalic and tetrabromoterephtalic acids) to investigate the influence of the halogen in the spin-transition temperature of SCO complexes. The crystal structures showed a 1D chain formed by the OH···O charge assisted hydrogen bonds between anions, which also form NH···O hydrogen bonds with the cations.…”

Section: Methodsmentioning

confidence: 99%

Spin Crossover in 3D Metal Centers Binding Halide-Containing Ligands: Magnetism, Structure and Computational Studies

2020

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The capability of a given substance to change its spin state by the action of a stimulus, such as a change in temperature, is by itself a very challenging property. Its interest is increased by the potential applications and the need to find sustainable functional materials. 3D transition metal complexes, mainly with octahedral geometry, display this property when coordinated to particular sets of ligands. The prediction of this behavior has been attempted by many authors. It is, however, made very difficult because spin crossover (SCO), as it is called, occurs most often in the solid state, where besides complexes, counter ions, and solvents are also present in many cases. Intermolecular interactions definitely play a major role in SCO. In this review, we decided to analyze SCO in mono- and binuclear transition metal complexes containing halogens as ligands or as substituents of the ligands. The aim was to try and find trends in the properties which might be correlated to halogen substitution patterns. Besides a revision of the properties, we analyzed structures and other information. We also tried to build a simple model to run Density Functional Theory (DFT) calculations and calculate several parameters hoping to find correlations between calculated indices and SCO data. Although there are many experimental studies and single-crystal X-ray diffraction structures, there are only few examples with the F, Cl, Br and series. When their intermolecular interactions were not very different, T1/2 (temperature with 50% high spin and 50% low spin states) usually increased with the calculated ligand field parameter (Δoct) within a given family. A way to predict SCO remains elusive.

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Section: Methodsmentioning

confidence: 99%

Spin Crossover in 3D Metal Centers Binding Halide-Containing Ligands: Magnetism, Structure and Computational Studies

2020

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“…The most essential need, namely RT operation, is achievable by controlling the spin transition temperature (T 1/2 ) . Thus, the various molecular design and modifications have been reported for the precise tuning of T 1/2 [22][23][24][25][26][27][28][29].…”

Section: Introductionmentioning

confidence: 99%

Iron(II) Spin Crossover Complex with the 1,2,3-Triazole-Containing Linear Pentadentate Schiff-Base Ligand and the MeCN Monodentate Ligand

et al. 2019

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A mononuclear iron(II) complex bearing the linear pentadentate N5 Schiff-base ligand containing two 1,2,3-triazole moieties and the MeCN monodentate ligand, [FeIIMeCN(L3-Me-3Ph)](BPh4)2·MeCN·H2O (1), have been prepared (L3-Me-3Ph = bis(N,N′-1-Phenyl-1H-1,2,3-triazol-4-yl-methylideneaminopropyl)methylamine). Variable-temperature magnetic susceptibility measurements revealed an incomplete one-step spin crossover (SCO) from the room-temperature low-spin (LS, S = 0) state to a mixture of the LS and high-spin (HS, S = 2) species at the higher temperature of around 400 K upon first heating, which is irreversible on the consecutive cooling mode. The magnetic modulation at around 400 K was induced by the crystal-to-amorphous transformation accompanied by the loss of lattice MeCN solvent, which was evident from powder X-ray diffraction (PXRD) studies and themogravimetry. The single-crystal X-ray diffraction studies showed that the complex is in the LS state (S = 0) between 296 and 387 K. In the crystal lattice, the complex-cations and B(1)Ph4− ions are alternately connected by intermolecular CH···π interactions between the methyl group of the MeCN ligand and phenyl groups of B(1)Ph4− ions, forming a 1D chain structure. The 1D chains are further connected by P4AE (parallel fourfold aryl embrace) interactions between two neighboring complex-cations, constructing a 2D extended structure. B(2)Ph4− ions and MeCN lattice solvents exist in the spaces of the 2D layer. DFT calculations verified that the 1,2,3-triazole-containing ligand L3-Me-3Ph gives a stronger ligand field around the octahedral coordination environment of the iron(II) ion than the analogous imidazole-containing ligand H2L2Me (= bis(N,N′-2-methylimidazol-4-yl-methylideneaminopropyl)methylamine) of the known compound [FeIIMeCN(H2L2Me)](BPh4)1.5·Cl0.5·0.5MeCN (2) reported by Matsumoto et al. (Nishi, K.; Fujinami, T.; Kitabayashi, A.; Matsumoto, N. Tetrameric spin crossover iron(II) complex constructed by imidazole⋯chloride hydrogen bonds. Inorg. Chem. Commun. 2011, 14, 1073–1076), resulting in the much higher spin transition temperature of 1 than that of 2.

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“…Phonsri and co-workers [13] describe the ethoxy substitution effect on homoleptic and heteroleptic Fe(III) SCO systems and find that the steric effect leads to less cooperative SCO conversions. Nakanishi and co-workers [14] investigate the halogen substitution effect on both the ligand and counter-anion for an Fe(III) SCO complex. They were successful at isolating and characterizing four isostructural SCO complexes and found that the substitution of the ligand may result in an inner electronic effect, whereas substitution of the counter-anion may create an outer chemical pressure effect.…”

mentioning

confidence: 99%

Spin-Crossover Complexes

Takahashi

2018

Inorganics

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Spin-crossover (SCO) is a spin-state switching phenomenon between a high-spin (HS) and low-spin (LS) electronic configurations in a transition metal center. The SCO phenomenon is widely recognized as an example of molecular bistability. The SCO compounds most widely studied are six-coordinate first-row transition metal complexes with d 4 -d 7 configurations. A relative small enthalpy variation between LS and HS states can be realized by coopetition between ligand field stabilization (LFS) and spin pairing energies, which is illustrated by the Tanabe-Sugano diagrams in common coordination chemistry textbooks. Since an entropy variation in spin multiplicity from LS to HS is always positive, an increase in temperature can induce the transformation in Gibbs free energy from a positive to a negative sign, at which point SCO conversion occurs from the LS to HS state.Cambi and co-workers' pioneering work on the anomalous magnetic behaviors of mononuclear Fe(III) dithiocarbamate complexes [1] was first recognized as SCO phenomena in the early 1930s. However, progress on SCO complexes awaited the dissemination of ligand field theory into coordination chemistry. The concept of controlling LFS energies by substitution with different field strength ligands resulted in the corroboration of SCO phenomena in some Co(II) and Fe(II) complexes in the early 1960s. Moreover, subsequent findings that pressure [2] and light [3] can induce an SCO phenomenon may attract attention to SCO complexes. In the 1990s the demonstration of device applications using the SCO complex [4] illuminated the potential of SCO complexes in future practical applications in memory, display, and sensing devices. Figure 1 shows the number of published articles per year whose titles or topics contain the words "spin-crossover," "spin equilibrium," or their derivatives. Studies concerning SCO complexes have apparently increased since the 1980s; moreover, the number has more rapidly developed after the 2000s. The fundamentals and applications of SCO complexes have attracted growing interest not only in inorganic coordination chemistry but also in a wide range of relevant research fields.

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Halogen Substituent Effect on the Spin-Transition Temperature in Spin-Crossover Fe(III) Compounds Bearing Salicylaldehyde 2-Pyridyl Hydrazone-Type Ligands and Dicarboxylic Acids

Cited by 11 publications

References 32 publications

Spin Crossover in 3D Metal Centers Binding Halide-Containing Ligands: Magnetism, Structure and Computational Studies

Spin Crossover in 3D Metal Centers Binding Halide-Containing Ligands: Magnetism, Structure and Computational Studies

Iron(II) Spin Crossover Complex with the 1,2,3-Triazole-Containing Linear Pentadentate Schiff-Base Ligand and the MeCN Monodentate Ligand

Spin-Crossover Complexes

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