Ambient-Temperature Spin-State Switching Achieved by Protonation of the Amino Group in [Fe(H2Bpz2)2(bipy-NH2)]

Luo, Yang‐Hui; Nihei, Masayuki; Wen, Gao-Ju; Sun, Bai-Wang; Oshio, Hiroki

doi:10.1021/acs.inorgchem.6b01193

Cited by 68 publications

(64 citation statements)

References 55 publications

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“…between the highest d π -orbital and the d z 2 -orbital, while the series 2 to 4 bearing different ester group turned out to reveal a relatively large energy splitting of ∆ and stronger π-acceptor properties, which stabilized the LS state 16 ( Figures S8-S12).…”

Section: X-ray Crystallographymentioning

confidence: 99%

Spin Crossover Behavior in a Homologous Series of Iron(II) Complexes Based on Functionalized Bipyridyl Ligands

et al. 2018

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A series of bulky substituted bipyridine-related iron(II) complexes [Fe(HBpz)(L)] (pz = pyrazolyl) were prepared, where L = 5,5'-dimethyl-2,2'-bipyridine (bipy-CH, 1), L = dimethyl-2,2'-bipyridyl-5,5'-dicarboxylate (MeObpydc, 2), L = diethyl-2,2'-bipyridyl-5,5'-dicarboxylate (EtObpydc, 3), or L = diisopropyl-2,2'-bipyridine-5,5'-dicarboxylate ( i-PrObpydc, 4). The crystal structures of five new iron(II) complexes were determined by X-ray diffraction: those of 1, 3, and 4 and two modifications of 3 (3B) and 4 (4B). Complexes 1 and 3B display incomplete spin crossover (SCO) behavior because of a freezing-in effect, whereas 3 and 4B undergo gradual and incomplete SCO behaviors. Complexes 2 and 4 show a completely gradual and steep SCO, respectively. Such different SCO behaviors can be attributed to an electronic substituent effect in the bipyridyl ligand conformation and a crystal packing effect. Importantly, the electronic substituent effect of the isopropyl acetate group and C-H···O supramolecular interactions in 4 contribute to a highly cooperative behavior, which leads to an abrupt thermally induced spin transition.

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Section: X-ray Crystallographymentioning

confidence: 99%

Spin Crossover Behavior in a Homologous Series of Iron(II) Complexes Based on Functionalized Bipyridyl Ligands

et al. 2018

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“…Different types of spin crossover curves: Left to right-abrupt and complete, gradual and complete, stepped and complete, abrupt and complete with hysteresis, and gradual and incomplete. Sustainability 2020, 12, 2512 3 of 50When the aim is to analyze the behavior of isolated molecules, SCO has been either studied in solution [38][39][40][41][42][43] or by depositing them on supports [44][45][46][47][48][49]. In solution, the distribution of spin states is assigned using a Boltzmann distribution, and a spin equilibrium is expected at different temperatures.…”

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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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“…Most recently, Lehn and co‐workers showed that the SCO behavior of a polynuclear {Fe 4 } grid‐type complex can be modified in response to pH by using protic ditopic ligands . And while mononuclear Fe II ‐complexes which reversibly respond to protonation/deprotonation are known, these systems can be switched between just two discrete states . Here, we describe a novel ligand design strategy employing an asymmetric Brønsted ligand (Scheme ) that can be used to isolate a mononuclear Fe‐complex with five independently accessible physical states.…”

Section: Figurementioning

confidence: 96%

A Brønsted‐Ligand‐Based Iron Complex as a Molecular Switch with Five Accessible States

et al. 2019

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A mononuclear FeII complex, prepared with a Brønsted diacid ligand, H2L (H2L=2‐[5‐phenyl‐1H‐pyrazole‐3‐yl] 6‐benzimidazole pyridine), shows switchable physical properties and was isolated in five different electronic states. The spin crossover (SCO) complex, [FeII(H2L)2](BF4)2 (1A), exhibits abrupt spin transition at T1/2=258 K, and treatment with base yields a deprotonated analogue [FeII(HL)2] (1B), which shows gradual SCO above 350 K. A range of FeIII analogues were also characterized. [FeIII(HL)(H2L)](BF4)Cl (1C) has an S=5/2 spin state, while the deprotonated complexes [FeIII(L)(HL)], (1D), and (TEA)[FeIII(L)2], (1E) exist in the low‐spin S=1/2 state. The electronic properties of the five complexes were fully characterized and we demonstrate in situ switching between multiple states in both solution and the solid‐state. The versatility of this simple mononuclear system illustrates how proton donor/acceptor ligands can vastly increase the range of accessible states in switchable molecular devices.

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Ambient-Temperature Spin-State Switching Achieved by Protonation of the Amino Group in [Fe(H₂Bpz₂)₂(bipy-NH₂)]

Cited by 68 publications

References 55 publications

Spin Crossover Behavior in a Homologous Series of Iron(II) Complexes Based on Functionalized Bipyridyl Ligands

Spin Crossover Behavior in a Homologous Series of Iron(II) Complexes Based on Functionalized Bipyridyl Ligands

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

A Brønsted‐Ligand‐Based Iron Complex as a Molecular Switch with Five Accessible States

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