Electronic, Magnetic, and Redox Properties and O2 Reactivity of Iron(II) and Nickel(II) o-Semiquinonate Complexes of a Tris(thioether) Ligand: Uncovering the Intradiol Cleaving Reactivity of an Iron(II) o-Semiquinonate Complex

Wang, Peng; Killian, Michelle M.; Saber, Mohamed R.; Qiu, Tian A.; Yap, Glenn P. A.; Popescu, Codrina V.; Rosenthal, Joel; Dunbar, Kim R.; Brunold, Thomas C.; Riordan, Charles G.

doi:10.1021/acs.inorgchem.7b01491

Cited by 11 publications

(6 citation statements)

References 81 publications

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“…While our J Ni–SQ of −291 cm –1 falls within the range of values reported for (five-coordinate) Ni–SQ complexes ( J Ni–SQ ≈ −244 to −525 cm –1 ), − the J SQ–SQ value determined for the nickel complex is 37% less than the corresponding J SQ–SQ value we reported for (ZnSQ) 2 Th 2 ( J SQ–SQ = −321 cm –1 ) at parity of the Th 2 bridge . In contrast to our analysis of the (NiSQ) 2 Th 2 data, the J SQ–SQ value for (ZnSQ) 2 Th 2 was obtained by fitting a three-state model (yellow box in Figure C), which includes the closed-shell quinoidal ground state, to magnetic susceptibility data of a crystalline (ZnSQ) 2 Th 2 sample.…”

Section: Results and Analysissupporting

confidence: 57%

Metal–Ligand Exchange Coupling Alters the Open-Shell Ligand Electronic Structure in a Bis(semiquinone) Complex

Miller,

Mengell,

Shultz

et al. 2024

Inorg. Chem.

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The electronic structure of the bis(dioxolene) bridging ligand -SQ 2 Th 2 -is responsive to metal−ligand magnetic exchange coupling. Comparison of the crystal structure of (NiSQ) 2 Th 2 to that of (ZnSQ) 2 Th 2 indicates an open-shell biradical ground state for the dinuclear Ni(II) complex compared to the closed-shell quinoidal character found in the dinuclear Zn(II) complex. Consistent with a comparison of bond lengths obtained by X-ray diffraction, the analysis of the variable-temperature magnetic susceptibility data for crystalline (NiSQ) 2 Th 2 yields reduced SQ−SQ radical−radical magnetic exchange coupling (J SQ−SQ = −203 cm −1 ) compared to that of (ZnSQ) 2 Th 2 (J SQ−SQ = −321 cm −1 ). The reduced SQ−SQ exchange coupling in (NiSQ) 2 Th 2 derives from an attenuation of the SQ spin densities, which in turn is derived from the Ni−SQ antiferromagnetic exchange interactions. This reduction in SQ−-SQ exchange that we observe for (NiSQ) 2 Th 2 correlates with an effective lengthening of the bridge unit by ∼2.1 Å relative to that of (ZnSQ) 2 Th 2 . This magnitude of the effective increase in the bridge distance is consistent with the (NiSQ) 2 Th 2 J SQ−SQ value lying between those of (ZnSQ) 2 Th 2 and (ZnSQ) 2 Th 3 . The ability to modulate spin populations on an organic radical via pairwise Ni−SQ magnetic exchange interactions is a general way to affect electronic coupling in the Th−Th bridge. Our results suggest that metal−radical exchange coupling represents a powerful mechanism for tuning organic molecular electronic structure, with important implications for molecular electronics and molecular electron transport.

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Section: Results and Analysissupporting

confidence: 57%

Metal–Ligand Exchange Coupling Alters the Open-Shell Ligand Electronic Structure in a Bis(semiquinone) Complex

Miller,

Mengell,

Shultz

et al. 2024

Inorg. Chem.

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“…Over the past few years, several of our laboratories have been studying first-row transition metal complexes of redox-active 1,2-dioxolene ligands due to an interest in their bioinspired O 2 activity. − During our interrogation of the electronic structures of the dioxolene complexes, we discovered the magnetic bistability of several five-coordinate Co(II)-semiquinonate radical complexes . These observations stimulated our interest in deducing the magnetic properties of the tris(thioether) ligand-containing transition metal complexes of redox-active ligands.…”

Section: Introductionmentioning

confidence: 99%

Molecular and Electronic Structures and Single-Molecule Magnet Behavior of Tris(thioether)–Iron Complexes Containing Redox-Active α-Diimine Ligands

et al. 2021

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Incorporating radical ligands into metal complexes is one of the emerging trends in the design of single-molecule magnets (SMMs). While significant effort has been expended to generate multinuclear transition metal-based SMMs with bridging radical ligands, less attention has been paid to mononuclear transition metal−radical SMMs. Herein, we describe the first α-diiminato radicalcontaining mononuclear transition metal SMM, namely, [κ 2 -PhTt tBu ] -Fe(AdNCHCHNAd) (1), and its analogue [κ 2 -PhTt tBu ]Fe-(CyNCHCHNCy) (2) (PhTt tBu = phenyltris(tert-butylthiomethyl)borate, Ad = adamantyl, and Cy = cyclohexyl). 1 and 2 feature nearly identical geometric and electronic structures, as shown by X-ray crystallography and electronic absorption spectroscopy. A more detailed description of the electronic structure of 1 was obtained through EPR and Mossbauer spectroscopies, SQUID magnetometry, and DFT, TD-DFT, and CAS calculations. 1 and 2 are best described as high-spin iron(II) complexes with antiferromagnetically coupled α-diiminato radical ligands. A strong magnetic exchange coupling between the iron(II) ion and the ligand radical was confirmed in 1, with an estimated coupling constant J < −250 cm −1 (J = −657 cm −1 , DFT). Calibrated CAS calculations revealed that the ground-state Fe(II)−α-diiminato radical configuration has significant ionic contributions, which are weighted specifically toward the Fe(I)-neutral α-diimine species. Experimental data and theoretical calculations also suggest that 1 possesses an easy-axis anisotropy, with an axial zero-field splitting parameter D in the range from −4 to−1 cm −1 . Finally, dynamic magnetic studies show that 1 exhibits slow magnetic relaxation behavior with an energy barrier close to the theoretical maximum, 2|D|. These results demonstrate that incorporating strongly coupled α-diiminato radicals into mononuclear transition metal complexes can be an effective strategy to prepare SMMs.

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“…In this case, the antiferromagnetic coupling is feasible between the monocationic radical ligand and both coordinated nickel atoms. A strong antiferromagnetic coupling between nickel and a radical ligand has been described before …”

Section: Resultsmentioning

confidence: 93%

Combining a Phenanthroline Moiety with Peralkylated Guanidine Residues: Homometallic Cu^II, Ni^II and Zn^II Halide Complexes with Site‐Differentiating Janus Head Ligands

et al. 2018

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The unique core portion of Janus head pro-ligands based on a tailored phenanthroline-bis(guanidine) architecture has been utilized to generate a multiplicity of homometallic copper(II), nickel(II) and zinc(II) complexes terminated by halide constituents. The bis-bidentate nitrogen donor ligands provide coordination sites with metal-differentiating properties which can be loaded successively starting with the phenanthroline interface as can be demonstrated by mononuclear species which form under metal deficient conditions. Furthermore, depending on both the alkylation and metalation stage of the guanidine residues comprising variants with tetramethyl-, tetraethyl-, dimethylethylene-, and dipentylene-guanidino function- [a] 5177 molecular structures, which are presented in Scheme 2, were identified by crystal structure analysis or mass spectrometry (see crystal structures and experimental section). Scheme 2. Synthesized mononuclear copper(II) (1-4) and nickel(II) (5 and 6) complexes.

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Electronic, Magnetic, and Redox Properties and O₂ Reactivity of Iron(II) and Nickel(II) o-Semiquinonate Complexes of a Tris(thioether) Ligand: Uncovering the Intradiol Cleaving Reactivity of an Iron(II) o-Semiquinonate Complex

Cited by 11 publications

References 81 publications

Metal–Ligand Exchange Coupling Alters the Open-Shell Ligand Electronic Structure in a Bis(semiquinone) Complex

Metal–Ligand Exchange Coupling Alters the Open-Shell Ligand Electronic Structure in a Bis(semiquinone) Complex

Molecular and Electronic Structures and Single-Molecule Magnet Behavior of Tris(thioether)–Iron Complexes Containing Redox-Active α-Diimine Ligands

Combining a Phenanthroline Moiety with Peralkylated Guanidine Residues: Homometallic Cu^II, Ni^II and Zn^II Halide Complexes with Site‐Differentiating Janus Head Ligands

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Electronic, Magnetic, and Redox Properties and O2 Reactivity of Iron(II) and Nickel(II) o-Semiquinonate Complexes of a Tris(thioether) Ligand: Uncovering the Intradiol Cleaving Reactivity of an Iron(II) o-Semiquinonate Complex

Cited by 11 publications

References 81 publications

Metal–Ligand Exchange Coupling Alters the Open-Shell Ligand Electronic Structure in a Bis(semiquinone) Complex

Metal–Ligand Exchange Coupling Alters the Open-Shell Ligand Electronic Structure in a Bis(semiquinone) Complex

Molecular and Electronic Structures and Single-Molecule Magnet Behavior of Tris(thioether)–Iron Complexes Containing Redox-Active α-Diimine Ligands

Combining a Phenanthroline Moiety with Peralkylated Guanidine Residues: Homometallic CuII, NiII and ZnII Halide Complexes with Site‐Differentiating Janus Head Ligands

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Electronic, Magnetic, and Redox Properties and O₂ Reactivity of Iron(II) and Nickel(II) o-Semiquinonate Complexes of a Tris(thioether) Ligand: Uncovering the Intradiol Cleaving Reactivity of an Iron(II) o-Semiquinonate Complex

Combining a Phenanthroline Moiety with Peralkylated Guanidine Residues: Homometallic Cu^II, Ni^II and Zn^II Halide Complexes with Site‐Differentiating Janus Head Ligands