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Molecular S = 2 High-Spin, S = 0 Low-Spin and S = 0 ⇄ 2 Spin-Transition/-Crossover Nickel(II)-Bis(nitroxide) Coordination Compounds. INORGANICS 2021. [DOI: 10.3390/inorganics9020010] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022] Open
Abstract
Heterospin systems have a great advantage in frontier orbital engineering since they utilize a wide diversity of paramagnetic chromophores and almost infinite combinations and mutual geometries. Strong exchange couplings are expected in 3d–2p heterospin compounds, where the nitroxide (aminoxyl) oxygen atom has a direct coordination bond with a nickel(II) ion. Complex formation of nickel(II) salts and tert-butyl 2-pyridyl nitroxides afforded a discrete 2p–3d–2p triad. Ferromagnetic coupling is favored when the magnetic orbitals, nickel(II) dσ and radical π*, are arranged in a strictly orthogonal fashion, namely, a planar coordination structure is characterized. In contrast, a severe twist around the coordination bond gives an orbital overlap, resulting in antiferromagnetic coupling. Non-chelatable nitroxide ligands are available for highly twisted and practically diamagnetic complexes. Here, the Ni–O–N–Csp2 torsion (dihedral) angle is supposed to be a useful metric to describe the nickel ion dislocated out of the radical π* nodal plane. Spin-transition complexes exhibited a planar coordination structure in a high-temperature phase and a nonplanar structure in a low-temperature phase. The gradual spin transition is described as a spin equilibrium obeying the van’t Hoff law. Density functional theory calculation indicates that the energy level crossing of the high- and low-spin states. The optimized structures of diamagnetic and high-spin states well agreed with the experimental large and small torsions, respectively. The novel mechanism of the present spin transition lies in the ferro-/antiferromagnetic coupling switch. The entropy-driven mechanism is plausible after combining the results of the related copper(II)-nitroxide compounds. Attention must be paid to the coupling parameter J as a variable of temperature in the magnetic analysis of such spin-transition materials. For future work, the exchange coupling may be tuned by chemical modification and external stimulus, because it has been clarified that the parameter is sensitive to the coordination structure and actually varies from 2J/kB = +400 K to −1400 K.
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Kashiro A, Kohno W, Ishida T. Odd–Even Effect on the Spin-Crossover Temperature in Iron(II) Complex Series Involving an Alkylated or Acyloxylated Tripodal Ligand. Inorg Chem 2020; 59:10163-10171. [DOI: 10.1021/acs.inorgchem.0c01296] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/21/2023]
Affiliation(s)
- Atsushi Kashiro
- Department of Engineering Science, The University of Electro-Communications, Chofu, Tokyo 182-8585, Japan
| | - Wakana Kohno
- Department of Engineering Science, The University of Electro-Communications, Chofu, Tokyo 182-8585, Japan
| | - Takayuki Ishida
- Department of Engineering Science, The University of Electro-Communications, Chofu, Tokyo 182-8585, Japan
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Kyoden Y, Homma Y, Ishida T. High-Spin and Incomplete Spin-Crossover Polymorphs in Doubly Chelated [Ni(L) 2Br 2] (L = tert-Butyl 5-Phenyl-2-pyridyl Nitroxide). Inorg Chem 2019; 58:10743-10755. [PMID: 31368687 DOI: 10.1021/acs.inorgchem.9b00885] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
Abstract
Complexation of nickel(II) bromide with tert-butyl 5-phenyl-2-pyridyl nitroxide (phpyNO) gave two morphs of doubly chelated [Ni(phpyNO)2Br2] as a 2p-3d-2p heterospin triad. The α phase crystallizes in the orthorhombic space group Pbcn. An asymmetric unit involves a half-molecule. The torsion angle around Ni-O-N-C2py is as small as 6.5(3)° at 100 K and 7.0(6)° at 400 K, guaranteeing an orthogonal arrangement between the magnetic radical π* and metal 3dx2-y2 and 3dz2 orbitals. Magnetic study revealed the high-spin ground state with the exchange coupling constant 2J/kB = +288(5) K, on the basis of a symmetrical spin Hamiltonian. The β phase crystallizes in the monoclinic space group P21/n. The whole molecule is an independent unit. The Ni-O-N-C2py torsion angles are 24.2(6) and 37.2(5)° at 100 K and 10.4(7) and 25.9(6)° at 400 K. A magnetic study revealed a very gradual and nonhysteretic spin transition. An analysis based on the van't Hoff equation gave a successful fit with the spin-crossover temperature of 134(1) K, although the susceptibility did not reach the theoretical high-spin value at 400 K. Density functional theory calculation on the β phase showed ground Stotal = 0 in the low-temperature structure while Stotal = 2 in the high-temperature structure, supporting the synchronized exchange coupling switch on both sides. Consequently, the β phase can be recognized as an "incomplete spin crossover" material, as a result of conflicting thermal depopulation effects in a high-temperature region.
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Affiliation(s)
- Yukiya Kyoden
- Department of Engineering Science , The University of Electro-Communications , Chofu, Tokyo 182-8585 , Japan
| | - Yuta Homma
- Department of Engineering Science , The University of Electro-Communications , Chofu, Tokyo 182-8585 , Japan
| | - Takayuki Ishida
- Department of Engineering Science , The University of Electro-Communications , Chofu, Tokyo 182-8585 , Japan
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Kashiro A, Kyoden Y, Okazawa A, Ishida T. Moving Organic Molecules in Crystalline Solids: Gradual Structural Transition and Spin Transition/Crossover. J SYN ORG CHEM JPN 2019. [DOI: 10.5059/yukigoseikyokaishi.77.684] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Affiliation(s)
| | | | | | - Takayuki Ishida
- Department of Engineering Science, The University of Electro-Communications
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Kashiro A, Some K, Kobayashi Y, Ishida T. Iron(II) and 1,1,1-Tris(2-pyridyl)nonadecane Complex Showing an Order-Disorder-Type Structural Transition and Spin-Crossover Synchronized over Both Conformers. Inorg Chem 2019; 58:7672-7676. [PMID: 31185543 DOI: 10.1021/acs.inorgchem.9b01146] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The title compound (Me4N)[Fe{(2-py)3C- n-C18H37}(NCS)3] having a C18 chain underwent spin-crossover (SCO). There are two crystallographically independent molecules in a triclinic cell at 100 K but only one in a monoclinic cell at 300 K. The complex showed a gradual one-step SCO in the same temperature region as that of the structural transition. The SCO is supported with the 57Fe Mössbauer spectroscopy. The molecules are differentiated on cooling, but the SCO was synchronized.
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Affiliation(s)
- Atsushi Kashiro
- Department of Engineering Science , The University of Electro-Communications , Chofu , Tokyo 182-8585 , Japan
| | - Kanako Some
- Department of Engineering Science , The University of Electro-Communications , Chofu , Tokyo 182-8585 , Japan
| | - Yoshio Kobayashi
- Department of Engineering Science , The University of Electro-Communications , Chofu , Tokyo 182-8585 , Japan
| | - Takayuki Ishida
- Department of Engineering Science , The University of Electro-Communications , Chofu , Tokyo 182-8585 , Japan
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Galadzhun I, Kulmaczewski R, Cespedes O, Yamada M, Yoshinari N, Konno T, Halcrow MA. 2,6-Bis(pyrazol-1-yl)pyridine-4-carboxylate Esters with Alkyl Chain Substituents and Their Iron(II) Complexes. Inorg Chem 2018; 57:13761-13771. [DOI: 10.1021/acs.inorgchem.8b02289] [Citation(s) in RCA: 24] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Iurii Galadzhun
- School of Chemistry, University of Leeds, Woodhouse Lane, Leeds LS2 9JT, U.K
| | - Rafal Kulmaczewski
- School of Chemistry, University of Leeds, Woodhouse Lane, Leeds LS2 9JT, U.K
| | - Oscar Cespedes
- School of Physics and Astronomy, University of Leeds, E. C. Stoner Building, Leeds LS2 9JT, U.K
| | - Mihoko Yamada
- Department of Chemistry, Graduate School of Science, Osaka University, Toyonaka, Osaka 560-0043, Japan
| | - Nobuto Yoshinari
- Department of Chemistry, Graduate School of Science, Osaka University, Toyonaka, Osaka 560-0043, Japan
| | - Takumi Konno
- Department of Chemistry, Graduate School of Science, Osaka University, Toyonaka, Osaka 560-0043, Japan
| | - Malcolm A. Halcrow
- School of Chemistry, University of Leeds, Woodhouse Lane, Leeds LS2 9JT, U.K
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Kimura A, Ishida T. Spin-Crossover Temperature Predictable from DFT Calculation for Iron(II) Complexes with 4-Substituted Pybox and Related Heteroaromatic Ligands. ACS OMEGA 2018; 3:6737-6747. [PMID: 31458846 PMCID: PMC6644749 DOI: 10.1021/acsomega.8b01095] [Citation(s) in RCA: 36] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 05/23/2018] [Accepted: 06/08/2018] [Indexed: 06/10/2023]
Abstract
Spin-crossover (SCO) is a reversible transition between low and high spin states by external stimuli such as heat. The SCO behavior and transition temperature (T 1/2) of a series of [FeII(X-pybox)2](ClO4)2 were studied to establish a methodology for ligand-field engineering, where X-pybox stands for 2,6-bis(oxazolin-2-yl)pyridine substituted with X at the 4-position of the pyridine ring. We utilized X = MeO, Me, 3-thienyl, Ph, H, MeS, 2-thienyl, N3, Cl, Br, 3-pyridyl, and 4-pyridyl. The solution susceptometry on five new derivatives with X = Me, 2-thienyl, N3, Br, and 3-pyridyl was performed in acetone, giving the SCO temperatures of 220, 260, 215, 280, and 270 K, respectively. The density-functional-theory molecular orbital (MO) calculation was performed on the ligands with geometry optimization. The atomic charge on the pyridine nitrogen atom [ρ(Npy)] was extracted from the natural orbital population analysis. Positive correlation appeared in the T 1/2 versus ρ(Npy) plot with R 2 = 0.734, being consistent with the analysis using the Hammett substituent constants (σp and σp +). This finding well agrees with the mechanism proposed: the rich electron density lifts the t2g energy level through the dπ-pπ interaction, resulting in a narrow t2g-eg energy gap and favoring the high-spin state and low T 1/2. The MO method was successfully applied to the known SCO-active iron(II) compounds involving 4-substituted 2,6-bis(pyrazol-1-yl)pyridines. A distinct positive correlation appeared in the T 1/2 versus ρ(Npy) plot. The comparison of correlation coefficients indicates that ρ(Npy) is a more reliable parameter than σp or σp + to predict a shift of T 1/2. Furthermore, this method can be more generalized by application to another known SCO family having 3-azinyl-4-p-tolyl-5-phenyl-1,2,4-triazole ligand series, where azinyl stands for a 2-azaaromatic ring. A good linear correlation was found in the T 1/2 versus ρ(NA) plot (NA is the ligating nitrogen atom in the azaaromatic ring). Finally, we will state a reason why the present treatment is competent to predict the SCO equilibrium position only by consideration on the electronic perturbation.
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Cobalt(II) Terpyridin-4′-yl Nitroxide Complex as an Exchange-Coupled Spin-Crossover Material. CRYSTALS 2018. [DOI: 10.3390/cryst8040155] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
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Tsubasa A, Otsuka S, Maekawa T, Takano R, Sakurai S, Deming TJ, Kuroiwa K. Development of hybrid diblock copolypeptide amphiphile/magnetic metal complexes and their spin crossover with lower-critical-solution-temperature(LCST)-type transition. POLYMER 2017. [DOI: 10.1016/j.polymer.2016.12.079] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
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Pybox-Iron(II) Spin-Crossover Complexes with Substituent Effects from the 4-Position of the Pyridine Ring (Pybox = 2,6-Bis(oxazolin-2-yl)pyridine). INORGANICS 2017. [DOI: 10.3390/inorganics5030052] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022] Open
Abstract
Spin-crossover (SCO) behavior of a series of [Fe(X-pybox)2](ClO4)2 was investigated, where X-pybox stands for 4-X-substituted 2,6-bis(oxazolin-2-yl)pyridine with X = H, Cl, Ph, CH3O, and CH3S. We confirmed that the mother compound [Fe(H-pybox)2](ClO4)2 underwent SCO above room temperature. After X was introduced, the SCO temperatures (T1/2) were modulated as 310, 230, and 330 K for X = Cl, Ph, and CH3S, respectively. The CH3O derivative possessed the high-spin state down to 2 K. Crystallographic analysis for X = H, Cl, CH3O, and CH3S was successful, being consistent with the results of the magnetic study. Distorted coordination structures stabilize the HS (high-spin) state, and the highest degree of the coordination structure distortion is found in the CH3O derivative. A plot of T1/2 against the Hammett substituent constant σp showed a positive relation. Solution susceptometry was also performed to remove intermolecular interaction and rigid crystal lattice effects, and the T1/2’s were determined as 260, 270, 240, 170, and 210 K for X = H, Cl, Ph, CH3O, and CH3S, respectively, in acetone. The substituent effect on T1/2 became very distinct, and it is clarified that electron-donating groups stabilize the HS state.
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Spin-Crossover Hysteresis of [FeII(LHiPr)2(NCS)2] (LHiPr = N-2-Pyridylmethylene-4-Isopropylaniline) Accompanied by Isopropyl Conformation Isomerism. MAGNETOCHEMISTRY 2015. [DOI: 10.3390/magnetochemistry1010017] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
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Synthesis, characterization and antimicrobial properties of lipophilic palladium complexes bearing iminopyridine ligands. TRANSIT METAL CHEM 2015. [DOI: 10.1007/s11243-015-9977-3] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/23/2022]
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Yamasaki M, Ishida T. First Iron(II) Spin-crossover Complex with an N5S Coordination Sphere. CHEM LETT 2015. [DOI: 10.1246/cl.150301] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Affiliation(s)
- Masaru Yamasaki
- Department of Engineering Science, The University of Electro-Communications
| | - Takayuki Ishida
- Department of Engineering Science, The University of Electro-Communications
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Yamasaki M, Ishida T. Spin-crossover thermal hysteresis and light-induced effect on iron(II) complexes with tripodal tris(2-pyridyl)methanol. Polyhedron 2015. [DOI: 10.1016/j.poly.2014.10.013] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/24/2022]
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Schulte KA, Fiedler SR, Shores MP. Solvent Dependent Spin-State Behaviour via Hydrogen Bonding in Neutral FeII Diimine Complexes. Aust J Chem 2014. [DOI: 10.1071/ch14145] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
Abstract
We report the syntheses, structures, and magnetic properties of cis-[Fe(pizR)2(NCS)2] complexes based on the pyridyl imidazoline ligands 2-(2′-pyridinyl)-4,5-dihydroimidazole (pizH, 1) and 2-(2′-pyridinyl)-4,5-dihydro-1-methylimidazole (pizMe, 2). The ligands, complexes, and magnetic measurements are chosen to separate hydrogen-bonding and intrinsic ligand field properties, so as to improve our understanding of the effect of hydrogen-bonding interactions on spin-state switching. In the solid state, both complexes are high spin between 5 and 300 K. In deuterated methanol and acetonitrile solutions, both complexes show gradual thermal spin crossover. Complex 1, capable of hydrogen bonding, shows solvent-sensitive spin crossover, whereas spin crossover in the methylated analogue 2 is insensitive to solvent identity.
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Hirosawa N, Oso Y, Ishida T. Spin Crossover and Light-induced Excited Spin-state Trapping Observed for an Iron(II) Complex Chelated with Tripodal Tetrakis(2-pyridyl)methane. CHEM LETT 2012. [DOI: 10.1246/cl.2012.716] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Affiliation(s)
- Naoki Hirosawa
- Department of Engineering Science, The University of Electro-Communications
| | - Yuya Oso
- Department of Engineering Science, The University of Electro-Communications
| | - Takayuki Ishida
- Department of Engineering Science, The University of Electro-Communications
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Djukic B, Seda T, Gorelsky SI, Lough AJ, Lemaire MT. π-Extended and Six-Coordinate Iron(II) Complexes: Structures, Magnetic Properties, and the Electrochemical Synthesis of a Conducting Iron(II) Metallopolymer. Inorg Chem 2011; 50:7334-43. [DOI: 10.1021/ic2010503] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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Shejwalkar P, Rath NP, Bauer EB. New iron(ii) α-iminopyridine complexes and their catalytic activity in the oxidation of activated methylene groups and secondary alcohols to ketones. Dalton Trans 2011; 40:7617-31. [DOI: 10.1039/c1dt10387c] [Citation(s) in RCA: 48] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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