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Stabilization of intermediate spin states in mixed-valent diiron dichalcogenide complexes. Nat Chem 2022; 14:328-333. [PMID: 35058610 PMCID: PMC8898764 DOI: 10.1038/s41557-021-00853-5] [Citation(s) in RCA: 9] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/19/2021] [Accepted: 11/03/2021] [Indexed: 11/24/2022]
Abstract
The electronic structure and ground spin states, S, observed for mixed-valent iron–sulfur dimers (FeII-FeIII) are typically determined by the Heisenberg exchange interaction, J, that couples the magnetic interaction of the two metal centres either ferromagnetically (J > 0, S = 9/2) or antiferromagnetically (J < 0, S = 1/2). In the case of antiferromagnetically coupled iron centres, stabilization of the high-spin S = 9/2 ground state is also feasible through a Heisenberg double-exchange interaction, B, which lifts the degeneracy of the Heisenberg spin states. This theorem also predicts intermediate spin states for mixed-valent dimers, but those have so far remained elusive. Herein, we describe the structural, electron paramagnetic resonance and Mössbauer spectroscopic, and magnetic characterization of a series of mixed-valent complexes featuring [Fe2Q2]+ (Q = S2–, Se2–, Te2–), where the Se and Te complexes favour S = 3/2 spin states. The incorporation of heavier chalcogenides in this series reveals a delicate balance of antiferromagnetic coupling, Heisenberg double-exchange and vibronic coupling. ![]()
Despite extensive investigations of mixed-valence complexes, molecules with intermediate spin states have remained elusive. Now, selenium- and tellurium-bridged mixed-valent iron dimers have been prepared in which a balance of Heisenberg exchange and double-exchange coupling of the unpaired electron, combined with moderate vibronic contributions, stabilizes S = 3/2 ground spin states.
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2
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A Mixed Valence Co IICo III2 Field-Supported Single Molecule Magnet: Solvent-Dependent Structural Variation. Molecules 2021; 26:molecules26041060. [PMID: 33670480 PMCID: PMC7922140 DOI: 10.3390/molecules26041060] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/31/2021] [Revised: 02/10/2021] [Accepted: 02/14/2021] [Indexed: 11/25/2022] Open
Abstract
One-pot reaction of the Schiff base N,N’-ethylene bis(salicylaldimine) (H2L), CoCl2.6H2O, and [Ph2SnCl2] in acetone produces the mixed valence CoIICoIII2 compound [CoIICoIII2(μ-L)2(Ph)2(μ-Cl)2]·(CH3)2CO·H2O (1). Our recent study already revealed that the same reaction mixtures in methanol or ethanol produced a heterometallic SnIVCoIII (2) or monometallic CoIII complex (3), respectively. Comparison of these organometallic systems shows that the 2,1-intermetallic Ph shift occurs in any of those solvents, but their relevant structural features (mononuclear, dinuclear-heterometallic, and trinuclear mixed valence) are solvent dependent. Geometrical structural rotation is also discussed among the related organometallic CoIICoIII2 systems. The AC magnetic susceptibility measurements indicate that 1 is a single molecule magnet (SMM), exhibiting a field-induced slow magnetic relaxation with two modes. The relaxation time for the low-frequency channel is as slow as τ~0.6 s at T = 2.0 K and BDC = 1.0 T.
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3
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Wong JWL, Hua S, Demeshko S, Dechert S, Ye S, Meyer F. Bis(pyrazolato) Bridged Diiron Complexes: Ferromagnetic Coupling in a Mixed‐Valent HS‐Fe
II
/LS‐Fe
III
Dinuclear Complex. Eur J Inorg Chem 2020. [DOI: 10.1002/ejic.202000697] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Affiliation(s)
- Joanne W. L. Wong
- Institut für Anorganische Chemie Georg‐August‐Universität Göttingen Tammannstrasse 4 37077 Göttingen Germany
| | - Shao‐An Hua
- Institut für Anorganische Chemie Georg‐August‐Universität Göttingen Tammannstrasse 4 37077 Göttingen Germany
| | - Serhiy Demeshko
- Institut für Anorganische Chemie Georg‐August‐Universität Göttingen Tammannstrasse 4 37077 Göttingen Germany
| | - Sebastian Dechert
- Institut für Anorganische Chemie Georg‐August‐Universität Göttingen Tammannstrasse 4 37077 Göttingen Germany
| | - Shengfa Ye
- Max‐Planck Institut für Kohlenforschung Stiftstraße 34‐36 45470 Mülheim an der Ruhr Germany
| | - Franc Meyer
- Institut für Anorganische Chemie Georg‐August‐Universität Göttingen Tammannstrasse 4 37077 Göttingen Germany
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4
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Syntheses, Structures, and Catalytic Hydrocarbon Oxidation Properties of N-Heterocycle-Sulfonated Schiff Base Copper(II) Complexes. INORGANICS 2019. [DOI: 10.3390/inorganics7020017] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023] Open
Abstract
Reaction of the o-[(o-hydroxyphenyl)methylideneamino]benzenesulfonic acid (H2L) (1) with CuCl2·2H2O in the presence of pyridine (py) leads to [Cu(L)(py)(EtOH)] (2) which, upon further reaction with 2,2’-bipyridine (bipy), pyrazine (pyr), or piperazine (pip), forms [Cu(L)(bipy)]·MeOH (3), [Cu2(L)2(μ-pyr)(MeOH)2] (4), or [Cu2(L)2(μ-pip)(MeOH)2] (5), respectively. The Schiff base (1) and the metal complexes (2–5) are stabilized by a number of non-covalent interactions to form interesting H-bonded multidimensional polymeric networks (except 3), such as zigzag 1D chain (in 1), linear 1D chain (in 2), hacksaw double chain 1D (in 4) and 2D motifs (in 5). These copper(II) complexes (2–5) catalyze the peroxidative oxidation of cyclic hydrocarbons (cyclooctane, cyclohexane, and cyclohexene) to the corresponding products (alcohol and ketone from alkane; alcohols, ketone, and epoxide from alkene), under mild conditions. For the oxidation of cyclooctane with hydrogen peroxide as oxidant, used as a model reaction, the best yields were generally achieved for complex 3 in the absence of any promoter (20%) or in the presence of py or HNO3 (26% or 30%, respectively), whereas 2 displayed the highest catalytic activity in the presence of HNO3 (35%). While the catalytic reactions were significantly faster with py, the best product yields were achieved with the acidic additive.
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5
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Sánchez RH, Betley TA. Thermally Persistent High-Spin Ground States in Octahedral Iron Clusters. J Am Chem Soc 2018; 140:16792-16806. [PMID: 30403845 DOI: 10.1021/jacs.8b10181] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Chemical oxidation and reduction of the all-ferrous (HL)2Fe6 in THF affords isostructural, coordinatively unsaturated clusters of the type [(HL)2Fe6] n: [(HL)2Fe6][BArF24] (1, n = +1; where [BArF24]- = tetrakis[(3,5-trifluoromethyl)phenyl]borate), [Bu4N][(HL)2Fe6] (2a, n = -1), [P][(HL)2Fe6] (2b, n = -1; where [P]+ = tributyl(1,3-dioxolan-2-ylmethyl)phosphonium), and [Bu4N]2[(HL)2Fe6] (3, n = -2). Each member of the redox-transfer series was characterized by zero-field 57Fe Mössbauer spectroscopy, near-infrared spectroscopy, single-crystal X-ray crystallography, and magnetometry. Redox-directed trends are observed when comparing the structural metrics within the [Fe6] core. The metal octahedron [Fe6] decreases marginally in volume as the molecular reduction state increases as gauged by the Fe-Feavg distance varying from 2.608(11) Å ( n = +1) to 2.573(3) ( n = -2). In contrast, the mean Fe-N distances and ∠Fe-N-Fe angles correlate linearly with the [Fe6] oxidation level, or alternatively, the changes observed within the local Fe-N4 coordination planes vary linearly with the aggregate spin ground state. In general, as the spin ground state ( S) increases, the Fe-N(H)avg distances also increase. The structural metric perturbations within the [Fe6] core and measured spin ground states were rationalized extending the previously proposed molecular orbital diagram derived for (HL)2Fe6. Chemical reduction of the (HL)2Fe6 cluster results in an abrupt increase in spin ground state from S = 6 for the all-ferrous cluster, to S = 19/2 in the monoanionic 2b and S = 11 for the dianionic 3. The observation of asymmetric intervalence charge transfer bands in 3 provides further evidence of the fully delocalized ground state observed by 57Fe Mössbauer spectroscopy for all species examined (1-3). For each of the clusters examined within the electron-transfer series, the observed spin ground states thermally persist to 300 K. In particular, the S = 11 in dianionic 3 and S = 19/2 in the monoanionic 2b represent the highest spin ground states isolated up to room temperature known to date. The increase in spin ground state results from population of the antibonding orbital band comprised of the Fe-N σ* interactions. As such, the thermally persistent ground states arise from population of the resultant single spin manifolds in accordance with Hund's rules. The large spin ground states, indicative of strong ferromagnetic electronic alignment of the valence electrons, result from strong direct exchange electronic coupling mediated by Fe-Fe orbital overlap within the [Fe6] cores, equivalent to a strong double exchange magnetic coupling B for 3 that was calculated to be 309 cm-1.
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Affiliation(s)
- Raúl Hernández Sánchez
- Department of Chemistry and Chemical Biology , Harvard University , 12 Oxford Street , Cambridge , Massachusetts 02138 , United States
| | - Theodore A Betley
- Department of Chemistry and Chemical Biology , Harvard University , 12 Oxford Street , Cambridge , Massachusetts 02138 , United States
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6
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Paul A, Hazra S, Sharma G, Guedes da Silva MFC, Koch B, Pombeiro AJL. Unfolding biological properties of a versatile dicopper(II) precursor and its two mononuclear copper(II) derivatives. J Inorg Biochem 2017; 174:25-36. [PMID: 28599129 DOI: 10.1016/j.jinorgbio.2017.05.013] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/22/2017] [Revised: 05/26/2017] [Accepted: 05/30/2017] [Indexed: 11/30/2022]
Abstract
Synthesis, inter-conversions and biological study of the dichloro bridged dicopper(II) compound [CuLCl]2 (1) and its two mononuclear derivatives [CuLCl(H2O)]·H2O (2) and [CuLCl(py)] (3) (HL=2-(2-pyridylmethyleneamino)benzenesulfonic acid) are described. The dimeric compound 1 collapses into monomers 2 and 3 in the presence of coordinating solvents, water and pyridine, respectively, and 1 is regenerated upon simple stirring of 2 or 3 in methanol. The reactions of 1 with neutral (present study) and charged (earlier studies) ligands result in monomeric and multimeric compounds, respectively, attesting that it is a versatile dicopper(II) precursor. The anticancer activity of these copper complexes (1-3) was screened against lung (A-549) and breast (MDA-MB-231) human cancer cell lines. The IC50 (half maximal inhibitory concentration) value for one (3) of the compounds suggests preferential cytotoxicity against breast cancer MDA-MB-231 cell line. Furthermore, the IC50 value obtained for complex 3 is found to be almost two-fold times cytotoxic than the standard drug cisplatin. In addition, the underlying possible mechanism of its apoptosis-inducing efficacy in MDA-MB-231 cells has been rationalized by using flow cytometry (FACS) and Hoechst 33342/propidium iodide (PI) fluorescence staining. The stimulation of apoptotic induction for complex 3 has further been affirmed by reactive oxygen species (ROS) generation and mitochondrial aggregations studies.
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Affiliation(s)
- Anup Paul
- Centro de Química Estrutural, Complexo I, Instituto Superior Técnico, Universidade de Lisboa, Av. Rovisco Pais, 1049-001, Lisbon, Portugal
| | - Susanta Hazra
- Centro de Química Estrutural, Complexo I, Instituto Superior Técnico, Universidade de Lisboa, Av. Rovisco Pais, 1049-001, Lisbon, Portugal.
| | - Gunjan Sharma
- Department of Zoology, Institute of Science, Banaras Hindu University, Varanasi 221005, India
| | - M Fátima C Guedes da Silva
- Centro de Química Estrutural, Complexo I, Instituto Superior Técnico, Universidade de Lisboa, Av. Rovisco Pais, 1049-001, Lisbon, Portugal.
| | - Biplob Koch
- Department of Zoology, Institute of Science, Banaras Hindu University, Varanasi 221005, India.
| | - Armando J L Pombeiro
- Centro de Química Estrutural, Complexo I, Instituto Superior Técnico, Universidade de Lisboa, Av. Rovisco Pais, 1049-001, Lisbon, Portugal
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7
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Hazra S, Titiš J, Valigura D, Boča R, Mohanta S. Bis-phenoxido and bis-acetato bridged heteronuclear {Co(III)Dy(III)} single molecule magnets with two slow relaxation branches. Dalton Trans 2017; 45:7510-20. [PMID: 27046444 DOI: 10.1039/c6dt00848h] [Citation(s) in RCA: 39] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Abstract
Two bis-μ-phenoxido-bis-μ-acetato heterobimetallic {Co(III)Dy(III)} complexes and , formulated as [Co(III)Dy(III)L(μ-OAc)2(NO3)2] derived from the comparable hexadentate Schiff bases N,N'-ethylenebis(3-ethoxysalicylaldimine) and N,N'-ethylenebis(3-methoxysalicylaldimine) were synthesized and X-ray structure analysis confirms their nearly identical structures. These are the first examples of bis(μ-phenoxido)-bis(μ-carboxylato) {Co(III)Dy(III)} systems. The AC susceptibility measurements show that both complexes exhibit a field-induced slow magnetic relaxation with two relaxation branches. While the high-frequency process spans the usual range of the relaxation time for analogous single molecule magnets (τ0 ∼ 10(-7) s), the low-frequency branch is as slow as τ ∼ 0.1 s at T = 1.9 K and B = 0.2 T.
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Affiliation(s)
- Susanta Hazra
- Department of Chemistry, University of Calcutta, 92 Acharya Prafulla Chandra Road, Kolkata 700 009, India. and Centro de Química Estrutural, Instituto Superior Técnico, Universidade de Lisboa, Av. Rovisco Pais, 1049-001, Lisbon, Portugal
| | - Ján Titiš
- Department of Chemistry, FPV, University of SS Cyril and Methodius, Trnava, Slovakia.
| | - Dušan Valigura
- Department of Chemistry, FPV, University of SS Cyril and Methodius, Trnava, Slovakia.
| | - Roman Boča
- Department of Chemistry, FPV, University of SS Cyril and Methodius, Trnava, Slovakia.
| | - Sasankasekhar Mohanta
- Department of Chemistry, University of Calcutta, 92 Acharya Prafulla Chandra Road, Kolkata 700 009, India.
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8
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Deng YF, Han T, Xue W, Hayashi N, Kageyama H, Zheng YZ. An Ising iron(ii) chain exhibits a large finite-size energy barrier and "hard" magnetic behaviour. Dalton Trans 2017; 46:1449-1454. [PMID: 28074202 DOI: 10.1039/c6dt03943j] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
Abstract
One-dimensional spin chains featuring strong axial anisotropic magnetism are promising candidates for isolatable and miniatured information storage materials, the so-called single-chain magnets (SCMs). Here we show a mixed azido/carboxylato bridged metamagnetic iron(ii) chain [Fe(N3)2(4-mpc)]n (4-mpc = N-methylpyridinium-4-carboxylate) with a large energy barrier of 150 K, a large remnant magnetization (1.55Nβ) and coercivity (1.7 T at 2 K) for homo-spin SCMs. Heat capacity and Mössbauer spectroscopy studies corroborate the intrinsic nature of SCM behavior regardless of weak interchain magnetic interactions, which lead to the coexistence of metamagnetism but not long-range magnetic ordering. Moreover, detailed magnetic investigations indicate that the system is not only within the "Ising limit" but also in the "finite-size" regime.
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Affiliation(s)
- Yi-Fei Deng
- Frontier Institute of Science and Technology (FIST) and School of Science, State Key Laboratory for Mechanical Behavior of Materials, Xi'an Jiaotong University, Xi'an 710054, China.
| | - Tian Han
- Frontier Institute of Science and Technology (FIST) and School of Science, State Key Laboratory for Mechanical Behavior of Materials, Xi'an Jiaotong University, Xi'an 710054, China.
| | - Wei Xue
- School of Chemistry & Chemical Engineering, Sun Yat-Sen University, Guangzhou 510275, China
| | - Naoaki Hayashi
- Research Institute for Production Development, Shimogamo, Sakyo, Kyoto 606-0805, Japan and Institute for Integrated Cell-Material Sciences, Kyoto University, Sakyo, Kyoto 606-8501, Japan
| | - Hiroshi Kageyama
- Department of Energy and Hydrocarbon Chemistry, Kyoto University, Nishikyo-ku, Kyoto 615-8510, Japan and CREST, Japan Science and Technology Agency (JST), Kawaguchi, Saitama 332-0012, Japan
| | - Yan-Zhen Zheng
- Frontier Institute of Science and Technology (FIST) and School of Science, State Key Laboratory for Mechanical Behavior of Materials, Xi'an Jiaotong University, Xi'an 710054, China.
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9
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Hazra S, Martins LM, Guedes da Silva MFC, Pombeiro AJ. Sulfonated Schiff base dimeric and polymeric copper(II) complexes: Temperature dependent synthesis, crystal structure and catalytic alcohol oxidation studies. Inorganica Chim Acta 2017. [DOI: 10.1016/j.ica.2016.05.052] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
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10
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Hazra S, Paul A, Sharma G, Koch B, da Silva MFCG, Pombeiro AJL. Sulfonated Schiff base Sn(IV) complexes as potential anticancer agents. J Inorg Biochem 2016; 162:83-95. [PMID: 27338202 DOI: 10.1016/j.jinorgbio.2016.06.008] [Citation(s) in RCA: 34] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/07/2016] [Revised: 05/13/2016] [Accepted: 06/03/2016] [Indexed: 12/13/2022]
Abstract
Syntheses, crystal structures and biological activities of the diphenoxo-bridged diorgano dinuclear Sn(IV) compounds [Sn(Et)2(HL)(H2O)]2 (1) and [Sn(n-Bu)2(HL)(H2O)]2 (2) derived from the Schiff base 2-[(2,3-dihydroxyphenyl)methylideneamino]benzenesulfonic acid trihydrate (H3L·3H2O) are described. The monoprotonated form (HL2-) of the Schiff base behaves as O,O'-bidentate ligand, chelating the metal by the two phenoxo oxygen atoms. The hexacoordinated metal centres in 1 and 2 are bridged by a phenoxo oxygen and the remaining coordination positions are fulfilled by the other phenoxo oxygen, two organic groups (ethyl for 1 and n-butyl for 2) and a water molecule. A two dimensional zigzag sheet in 1 and three dimensional polymeric networks in H3L·3H2O and 2 are stabilized by a number of non-covalent, H-bonding and π⋯π stacking interactions. The DNA binding activities of these complexes have been studied by UV-vis and fluorescence spectroscopies. Their antiproliferative efficacies have been evaluated on A-549, HeLa and MDA-MB-231 cancer cell lines by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay. IC50 values (1.35±0.23, 2.43±0.54 and 1.74±0.04μM for 2) are indicative of a substantial cytotoxicity of 2, mainly towards the A-549 lung cancer cell line. The greater antiproliferative efficacy of 2has further been studied by fluorescence activated cell sorting (FACS) and nuclear morphology by Hoechst/propidium iodide (PI) double staining method. The possible mode of the apoptotic pathway for 2has been substantiated by the reactive oxygen species (ROS) generation studies.
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Affiliation(s)
- Susanta Hazra
- Centro de Química Estrutural, Instituto Superior Técnico, Universidade de Lisboa, Av. Rovisco Pais, 1049-001 Lisbon, Portugal.
| | - Anup Paul
- Centro de Química Estrutural, Instituto Superior Técnico, Universidade de Lisboa, Av. Rovisco Pais, 1049-001 Lisbon, Portugal
| | - Gunjan Sharma
- Department of Zoology, Faculty of Science, Banaras Hindu University, Varanasi 221 005, India
| | - Biplob Koch
- Department of Zoology, Faculty of Science, Banaras Hindu University, Varanasi 221 005, India.
| | - M Fátima C Guedes da Silva
- Centro de Química Estrutural, Instituto Superior Técnico, Universidade de Lisboa, Av. Rovisco Pais, 1049-001 Lisbon, Portugal.
| | - Armando J L Pombeiro
- Centro de Química Estrutural, Instituto Superior Técnico, Universidade de Lisboa, Av. Rovisco Pais, 1049-001 Lisbon, Portugal
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Sánchez RH, Bartholomew AK, Powers TM, Ménard G, Betley TA. Maximizing Electron Exchange in a [Fe3] Cluster. J Am Chem Soc 2016; 138:2235-43. [PMID: 26799500 PMCID: PMC5567842 DOI: 10.1021/jacs.5b12181] [Citation(s) in RCA: 36] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The one-electron reduction of ((tbs)L)Fe₃(thf)¹ furnishes [M][((tbs)L)Fe₃] ([M]⁺ = [(18-C-6)K(thf)₂]⁺ (1, 76%) or [(crypt-222)K]⁺ (2, 54%)). Upon reduction, the ligand (tbs)L⁶⁻ rearranges around the triiron core to adopt an almost ideal C₃-symmetry. Accompanying the ((tbs)L) ligand rearrangement, the THF bound to the neutral starting material is expelled, and the Fe-Fe distances within the trinuclear cluster contract by ∼0.13 Å in 1. Variable-temperature magnetic susceptibility data indicates a well-isolated S = 11/2 spin ground state that persists to room temperature. Slow magnetic relaxation is observed at low temperature as evidenced by the out-of-phase (χ(M)″) component of the alternating current (ac) magnetic susceptibility data and by the appearance of hyperfine splitting in the zero-field ⁵⁷Fe Mössbauer spectra at 4.2 K. Analysis of the ac magnetic susceptibility yields an effective spin reversal barrier (U(eff)) of 22.6(2) cm⁻¹, nearly matching the theoretical barrier of 38.7 cm⁻¹ calculated from the axial zero-field splitting parameter (D = -1.29 cm⁻¹) extracted from the reduced magnetization data. A polycrystalline sample of 1 displays three sextets in the Mössbauer spectrum at 4.2 K (H(ext) = 0) which converge to a single six-line pattern in a frozen 2-MeTHF glass sample, indicating a unique iron environment and thus strong electron delocalization. The spin ground state and ligand rearrangement are discussed within the framework of a fully delocalized cluster exhibiting strong double and direct exchange interactions.
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Affiliation(s)
- Raúl Hernández Sánchez
- Department of Chemistry and Chemical Biology, Harvard University, 12 Oxford Street, Cambridge, Massachusetts 02138, United States
| | - Amymarie K. Bartholomew
- Department of Chemistry and Chemical Biology, Harvard University, 12 Oxford Street, Cambridge, Massachusetts 02138, United States
| | | | | | - Theodore A. Betley
- Department of Chemistry and Chemical Biology, Harvard University, 12 Oxford Street, Cambridge, Massachusetts 02138, United States
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12
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Abstract
The field of single molecule magnetism remains predicated on super- and double exchange mechanisms to engender large spin ground states. An alternative approach to achieving high-spin architectures involves synthesizing weak-field clusters featuring close M-M interactions to produce a single valence orbital manifold. Population of this orbital manifold in accordance with Hund's rules could potentially yield thermally persistent high-spin ground states under which the valence electrons remain coupled. We now demonstrate this effect with a reduced hexanuclear iron cluster that achieves an S = 19/2 (χ(M)T ≈ 53 cm(3) K/mol) ground state that persists to 300 K, representing the largest spin ground state persistent to room temperature reported to date. The reduced cluster displays single molecule magnet behavior manifest in both variable-temperature zero-field (57)Fe Mössbauer and magnetometry with a spin reversal barrier of 42.5(8) cm(-1) and a magnetic blocking temperature of 2.9 K (0.059 K/min).
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Affiliation(s)
- Rauĺ Hernández Sánchez
- Department of Chemistry and Chemical Biology, Harvard University, 12 Oxford Street, Cambridge, Massachusetts 02138, United States
| | - Theodore A. Betley
- Department of Chemistry and Chemical Biology, Harvard University, 12 Oxford Street, Cambridge, Massachusetts 02138, United States
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13
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Gaudette AI, Jeon IR, Anderson JS, Grandjean F, Long GJ, Harris TD. Electron Hopping through Double-Exchange Coupling in a Mixed-Valence Diiminobenzoquinone-Bridged Fe2 Complex. J Am Chem Soc 2015; 137:12617-26. [DOI: 10.1021/jacs.5b07251] [Citation(s) in RCA: 43] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Affiliation(s)
- Alexandra I. Gaudette
- Department
of Chemistry, Northwestern University, Evanston, Illinois 60208-3113, United States
| | - Ie-Rang Jeon
- Department
of Chemistry, Northwestern University, Evanston, Illinois 60208-3113, United States
| | - John S. Anderson
- Department
of Chemistry, Northwestern University, Evanston, Illinois 60208-3113, United States
| | - Fernande Grandjean
- Department
of Chemistry, Missouri University of Science and Technology, University of Missouri, Rolla, Missouri 65409-0010, United States
| | - Gary J. Long
- Department
of Chemistry, Missouri University of Science and Technology, University of Missouri, Rolla, Missouri 65409-0010, United States
| | - T. David Harris
- Department
of Chemistry, Northwestern University, Evanston, Illinois 60208-3113, United States
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14
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Sasmal S, Roy S, Carrella L, Jana A, Rentschler E, Mohanta S. Structures and Magnetic Properties of Bis(μ‐phenoxido), Bis(μ‐phenoxido)‐μ‐carboxylato and Bis(μ‐phenoxido)bis(μ‐carboxylato) Fe
III
Ni
II
Compounds – Magnetostructural Correlations. Eur J Inorg Chem 2015. [DOI: 10.1002/ejic.201402866] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Affiliation(s)
- Sujit Sasmal
- Department of Chemistry, University of Calcutta, 92 A. P. C. Road, Kolkata 700 009, India, http://173.201.183.21/~cuchemistry/?page_id=239
| | - Shuvayan Roy
- Department of Chemistry, University of Calcutta, 92 A. P. C. Road, Kolkata 700 009, India, http://173.201.183.21/~cuchemistry/?page_id=239
| | - Luca Carrella
- Institut für Anorganische Chemie und Analytische Chemie, Johannes‐Gutenberg Universität Mainz, Duesbergweg 10‐14, 55128 Mainz, Germany, http://www.ak‐rentschler.chemie.uni‐mainz.de
| | - Arpita Jana
- Department of Chemistry, University of Calcutta, 92 A. P. C. Road, Kolkata 700 009, India, http://173.201.183.21/~cuchemistry/?page_id=239
| | - Eva Rentschler
- Institut für Anorganische Chemie und Analytische Chemie, Johannes‐Gutenberg Universität Mainz, Duesbergweg 10‐14, 55128 Mainz, Germany, http://www.ak‐rentschler.chemie.uni‐mainz.de
| | - Sasankasekhar Mohanta
- Department of Chemistry, University of Calcutta, 92 A. P. C. Road, Kolkata 700 009, India, http://173.201.183.21/~cuchemistry/?page_id=239
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Hazra S, Martins LMDRS, Guedes da Silva MFC, Pombeiro AJL. Sulfonated Schiff base copper(ii) complexes as efficient and selective catalysts in alcohol oxidation: syntheses and crystal structures. RSC Adv 2015. [DOI: 10.1039/c5ra19498a] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
Alcohol oxidation properties of four copper complexes (2–5) derived from the sulfonated Schiff base H2L·3H2O (1) are described. A quantitative conversion of 1-phenylethanol was obtained with 4 within 20 min of low power MW irradiation.
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Affiliation(s)
- Susanta Hazra
- Centro de Química Estrutural
- Instituto Superior Técnico
- Universidade de Lisboa
- Lisboa
- Portugal
| | | | | | - Armando J. L. Pombeiro
- Centro de Química Estrutural
- Instituto Superior Técnico
- Universidade de Lisboa
- Lisboa
- Portugal
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16
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Hazra S, Karmakar A, Guedes da Silva MFC, Dlháň Ľ, Boča R, Pombeiro AJ. Dinuclear based polymeric copper(II) complexes derived from a Schiff base ligand: effect of secondary bridging moieties on geometrical orientations and magnetic properties. INORG CHEM COMMUN 2014. [DOI: 10.1016/j.inoche.2014.05.025] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/25/2022]
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17
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Jeon IR, Park JG, Xiao DJ, Harris TD. An azophenine radical-bridged Fe2 single-molecule magnet with record magnetic exchange coupling. J Am Chem Soc 2013; 135:16845-8. [PMID: 24164631 DOI: 10.1021/ja409927v] [Citation(s) in RCA: 118] [Impact Index Per Article: 10.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/20/2023]
Abstract
One-electron reduction of the complex [(TPyA)2Fe(II)2((NPh)L(2-))](2+) (TPyA = tris(2-pyridylmethyl)amine, (NPh)LH2 = azophenine = N,N',N",N'''-tetraphenyl-2,5-diamino-1,4-diiminobenzoquinone) affords the complex [(TPyA)2Fe(II)2((NPh)L(3-•))](+). X-ray diffraction and Mössbauer spectroscopy confirm that the reduction occurs on (NPh)L(2-) to give an S = 1/2 radical bridging ligand. Dc magnetic susceptibility measurements demonstrate the presence of extremely strong direct antiferromagnetic exchange between S = 2 Fe(II) centers and (NPh)L(3-•) in the reduced complex, giving an S = 7/2 ground state with an estimated coupling constant magnitude of |J| ≥ 900 cm(-1). Mössbauer spectroscopy and ac magnetic susceptibility reveal that this complex behaves as a single-molecule magnet with a spin relaxation barrier of U(eff) = 50(1) cm(-1). To our knowledge, this complex exhibits by far the strongest magnetic exchange coupling ever to be observed in a single-molecule magnet.
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Affiliation(s)
- Ie-Rang Jeon
- Department of Chemistry, Northwestern University , Evanston Illinois 60208-3113, United States
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18
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Zadrozny JM, Xiao DJ, Long JR, Atanasov M, Neese F, Grandjean F, Long GJ. Mössbauer Spectroscopy as a Probe of Magnetization Dynamics in the Linear Iron(I) and Iron(II) Complexes [Fe(C(SiMe3)3)2]1–/0. Inorg Chem 2013; 52:13123-31. [DOI: 10.1021/ic402013n] [Citation(s) in RCA: 87] [Impact Index Per Article: 7.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
| | | | | | - Mihail Atanasov
- Max-Planck Institut fur Chemische Energiekonversion, Mulheim an der Ruhr, D-45470, Germany
- Institute of General and Inorganic Chemistry, Bulgarian Academy of Sciences, Acad. Georgi Bontchev Str 11, 1113 Sofia, Bulgaria
| | - Frank Neese
- Max-Planck Institut fur Chemische Energiekonversion, Mulheim an der Ruhr, D-45470, Germany
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19
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Hazra S, Bhattacharya S, Singh MK, Carrella L, Rentschler E, Weyhermueller T, Rajaraman G, Mohanta S. Syntheses, Structures, Magnetic Properties, and Density Functional Theory Magneto-Structural Correlations of Bis(μ-phenoxo) and Bis(μ-phenoxo)-μ-acetate/Bis(μ-phenoxo)-bis(μ-acetate) Dinuclear FeIIINiII Compounds. Inorg Chem 2013; 52:12881-92. [DOI: 10.1021/ic400345w] [Citation(s) in RCA: 43] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Susanta Hazra
- Department of Chemistry, University of Calcutta, 92 A. P. C. Road, Kolkata 700 009, India
| | - Sagarika Bhattacharya
- Department of Chemistry, University of Calcutta, 92 A. P. C. Road, Kolkata 700 009, India
| | - Mukesh Kumar Singh
- Department of Chemistry, Indian Institute of Technology Bombay, Powai, Mumbai 400076, India
| | - Luca Carrella
- Institut für
Anorganische Chemie und Analytische Chemie, Johannes-Gutenberg Universität Mainz, Duesbergweg 10-14, D-55128 Mainz, Germany
| | - Eva Rentschler
- Institut für
Anorganische Chemie und Analytische Chemie, Johannes-Gutenberg Universität Mainz, Duesbergweg 10-14, D-55128 Mainz, Germany
| | - Thomas Weyhermueller
- Max-Planck-Institut für Chemische Energiekonversion, Stiftstr 34-36, 45470 Mülheim an der Ruhr, Germany
| | - Gopalan Rajaraman
- Department of Chemistry, Indian Institute of Technology Bombay, Powai, Mumbai 400076, India
| | - Sasankasekhar Mohanta
- Department of Chemistry, University of Calcutta, 92 A. P. C. Road, Kolkata 700 009, India
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20
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Barrero CA, García KE. New direct method for evaluating recoilless f-factors of two iron-sites in Fe-bearing compounds using Mössbauer spectrometry. J Chem Phys 2013; 139:034703. [PMID: 23883048 DOI: 10.1063/1.4813282] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
We propose a new direct method for calculating simultaneously two recoilless f-factors of any iron-bearing compound relative to that of a reference material by collecting only a single-temperature Mössbauer spectrum. This methodology is comparatively much simpler than the usual one which requires taking Mössbauer spectra of the compound at several temperatures and subsequently fitting the temperature dependence of the subspectral area or the isomer shift data with a lattice vibrational model. We demonstrate the applicability of this new methodology in the case of three common iron-bearing compounds: magnetite, akaganeite and goethite, but of course this type of study can be extended to other materials. The two f-factors for each compound were related to iron ions located in sites of different origin: for magnetite, these were related to irons with two different oxidation states; for akaganeite to irons in two different crystallographic sites; and for goethite to irons in similar crystal sites but located in grains of different sizes. In the case of magnetite, we found that the f-factors for the Fe(3+) and Fe(2.5+) sites relative to that of metallic iron powder were of fFe (3+)∕fFe = 0.97 ± 0.05 and fFe (2.5+)∕fFe = 0.92 ± 0.05, respectively. Interestingly, the quotient of these two f-factors, i.e., fFe (2.5+)∕fFe (3+), is equal to 0.95 ± 0.05, which compares fairly well with a value reported in literature obtained using the complex methodology based on the temperature dependence of the absolute subspectral area and the Debye approximation. For akaganeite, the f-factors of the doublet 1, D1, and doublet 2, D2, sites relative to that of metallic iron powder were of fD 1∕fFe = 0.95 ± 0.08 and fD 2∕fFe = 0.98 ± 0.15, respectively. And for goethite we found that the f-factors of the sextet 1, G1, and sextet 2, G2, sites relative to that of metallic iron powder were of fG 1∕fFe = 0.80 ± 0.02 and fG 2∕fFe = 0.80 ± 0.02, respectively. The similarity of these last two factors is perhaps due to a sharp distribution of large grains.
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Affiliation(s)
- C A Barrero
- Grupo de Estado Sólido, Facultad de Ciencias Exactas y Naturales, Universidad de Antioquia UdeA, Calle 70 No 52-21, Medellín, Colombia
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21
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Jana A, Aliaga-Alcalde N, Ruiz E, Mohanta S. Structures, Magnetochemistry, Spectroscopy, Theoretical Study, and Catechol Oxidase Activity of Dinuclear and Dimer-of-Dinuclear Mixed-Valence MnIIIMnII Complexes Derived from a Macrocyclic Ligand. Inorg Chem 2013; 52:7732-46. [DOI: 10.1021/ic400916h] [Citation(s) in RCA: 56] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Arpita Jana
- Department of Chemistry, University of Calcutta, 92 A. P. C. Road, Kolkata 700
009, India
| | - Núria Aliaga-Alcalde
- Institució Catalana de Recerca i Estudis Avançats (ICREA), Institut de Ciència de Materials de Barcelona (ICMAB-CSIC)
Campus de la UAB, 08193 Bellaterra, Spain
| | - Eliseo Ruiz
- Departament de Química Inorgànica and
Institut de Recerca de Química Teòrica i Computacional, Universitat de Barcelona, Diagonal 645, E-08028 Barcelona,
Spain
| | - Sasankasekhar Mohanta
- Department of Chemistry, University of Calcutta, 92 A. P. C. Road, Kolkata 700
009, India
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22
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Majumder S, Mondal S, Lemoine P, Mohanta S. Dinuclear mixed-valence CoIIICoII complexes derived from a macrocyclic ligand: unique example of a CoIIICoII complex showing catecholase activity. Dalton Trans 2013; 42:4561-9. [DOI: 10.1039/c2dt32629a] [Citation(s) in RCA: 60] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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23
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Abstract
The symmetric, high-spin triiron complex ((Ph)L)Fe(3)(THF)(3) reacts with mild chemical oxidants (e.g., Ph(3)C-X, I(2)) to afford an asymmetric core, where one iron bears the halide ligand ((Ph)L)Fe(3)X(L) and the hexadentate ((Ph)L = MeC(CH(2)NPh-o-NPh)(3)) ligand has undergone significant rearrangement. In the absence of a suitable trapping ligand, the chlorine and bromine complexes form (μ-X)(2)-bridged structures of the type [((Ph)L)Fe(3)(μ-X)](2). In the trinuclear complexes, the halide-bearing iron site sits in approximate trigonal-bipyramidal (tbp) geometry, formed by two ((Ph)L) anilides and an exogenous solvent molecule. The two distal iron atoms reside in distorted square-planar sites featuring a short Fe-Fe separation at 2.301 Å, whereas the distance to the tbp site is substantially elongated (2.6-2.7 Å). Zero-field, (57)Fe Mössbauer analysis reveals the diiron unit as the locus of oxidation, while the tbp site bearing the halide ligand remains divalent. Magnetic data acquired for the series reveal that the oxidized diiron unit comprises a strongly coupled S = (3)/(2) unit that is weakly ferromagnetically coupled to the high-spin (S = 2) ferrous site, giving an overall S = (7)/(2) ground state for the trinuclear units.
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Affiliation(s)
- Emily V Eames
- Department of Chemistry and Chemical Biology, Harvard University, 12 Oxford Street, Cambridge, Massachusetts 02138, USA
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24
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A new tetraiminodiphenol macrocyclic ligand and its two dicopper(II) complexes: Syntheses, crystal structures, electrochemistry and magnetochemistry. J Mol Struct 2012. [DOI: 10.1016/j.molstruc.2012.04.003] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
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25
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Eames EV, Harris TD, Betley TA. Modulation of magnetic behavior vialigand-field effects in the trigonal clusters (PhL)Fe3L*3(L*= thf, py, PMe2Ph). Chem Sci 2012. [DOI: 10.1039/c1sc00492a] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
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