Strong magnetic exchange coupling in Ln<sub>2</sub> metallocenes attained by the <i>trans</i>-coordination of a tetrazinyl radical ligand

Mavragani, Niki; Kitos, Alexandros A.; Hrubý, J.; Hill, Stephen; Mansikkamäki, Akseli; Moilanen, Jani O.; Murugesu, Muralee

doi:10.1039/d3qi00290j

Cited by 5 publications

(5 citation statements)

References 67 publications

(114 reference statements)

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“…The Kramers nature of the ground state wave functions prevents their direct mixing, hence such species are nearly always EPR silent. 71 A similar effect due to an axial CF is expected for the Ho III complex (1) with an m J = ±8 quasi-doublet ground state and a sizable separation to the m J = ±7 excited states. However, a key difference in the Ho III case is that it is not a Kramers ion, meaning that the ±m J states can mix to the first order.…”

Section: Resultsmentioning

confidence: 59%

“…This results in an isolated ground doublet with a maximal m J = ±15/2 projection and a large barrier to magnetization reversal. The Kramers nature of the ground state wave functions prevents their direct mixing, hence such species are nearly always EPR silent . A similar effect due to an axial CF is expected for the Ho III complex ( 1 ) with an m J = ±8 quasi-doublet ground state and a sizable separation to the m J = ±7 excited states.…”

Section: Resultsmentioning

confidence: 71%

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Engineering Clock Transitions in Molecular Lanthanide Complexes

Stewart,

Canaj,

Liu

et al. 2024

J. Am. Chem. Soc.

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Molecular lanthanide (Ln) complexes are promising candidates for the development of next-generation quantum technologies. High-symmetry structures incorporating integer spin Ln ions can give rise to well-isolated crystal field quasi-doublet ground states, i.e., quantum two-level systems that may serve as the basis for magnetic qubits. Recent work has shown that symmetry lowering of the coordination environment around the Ln ion can produce an avoided crossing or clock transition within the ground doublet, leading to significantly enhanced coherence. Here, we employ single-crystal high-frequency electron paramagnetic resonance spectroscopy and high-level ab initio calculations to carry out a detailed investigation of the nine-coordinate complexes, [Ho III L 1 L 2 ], where L 1 = 1,4,7,10-tetrakis(2-pyridylmethyl)-1,4,7,10-tetraaza-cyclododecane and L 2 = F − (1) or [MeCN] 0 (2). The pseudo-4-fold symmetry imposed by the neutral organic ligand scaffold (L 1 ) and the apical anionic fluoride ion generates a strong axial anisotropy with an m J = ±8 ground-state quasi-doublet in 1, where m J denotes the projection of the J = 8 spin−orbital moment onto the ∼C 4 axis. Meanwhile, off-diagonal crystal field interactions give rise to a giant 116.4 ± 1.0 GHz clock transition within this doublet. We then demonstrate targeted crystal field engineering of the clock transition by replacing F − with neutral MeCN (2), resulting in an increase in the clock transition frequency by a factor of 2.2. The experimental results are in broad agreement with quantum chemical calculations. This tunability is highly desirable because decoherence caused by second-order sensitivity to magnetic noise scales inversely with the clock transition frequency.

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Section: Resultsmentioning

confidence: 59%

Section: Resultsmentioning

confidence: 71%

Engineering Clock Transitions in Molecular Lanthanide Complexes

Stewart,

Canaj,

Liu

et al. 2024

J. Am. Chem. Soc.

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“…For cis -structures, a coordination pocket with quadridentate coordination was common, whereas the ligand was almost in the same plane with a calculated dihedral angle (θ) of 7.249° (Figure S8). As for the trans -configuration, the ligand was severely distorted and not in the same plane (θ is 36.479°) when it exhibited tridentate coordination, affecting the symmetry of the complex. − The local coordination models of three Dy III ions of 1 were then analyzed (Figure S9), where Dy1 and Dy2 or Dy1 i and Dy2 ions were connected via the Dy 2 O 2 configuration, and Dy1 and Dy1 i were connected via a CH 3 COO – . To rationally regulate the structure of 1 , the formation process was reasonably speculated based on the single-crystal data and coordination configuration (Scheme a).…”

Section: Resultsmentioning

confidence: 99%

“…Among Ln III ions, Dy III -based SMMs demonstrate many remarkable properties. , The magnetic properties of SMMs are closely related to the electron cloud distribution of metal ions. For oblate Dy III –SMMs, a strong axial crystal field (CF) and weak equatorial ligand field are required to balance the electron cloud distribution. , However, for multicore systems, the magnetic coupling is complex because of the different anisotropy of central ions.…”

Section: Introductionmentioning

confidence: 99%

Structures and Single-Molecule Magnet Behavior of Dy₃ and Dy₄ Clusters Constructed by Different Dysprosium(III) Salts

Li,

Shi,

et al. 2024

Inorg. Chem.

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Using the Schiff base ligand H 2 L-pyra (N′-(2hydroxybenzoyl)pyrazine-2-carbohydrazonamide) with multiple dentate sites, the trinuclear Dy III -based complex [Dy 3 (HLpyra) 2 (L-pyra) 2 (CH 3 COO) 3 ]•2H 2 O (1) was synthesized. By analyzing the fragmented assembly process and fine-tuning the b r i d g i n g a n i o n s , c o m p l e x [ D y 4 ( H L -p y r a ) 2 ( L -p y ra) 4 2) with different nuclear numbers was successfully synthesized. Magnetic studies demonstrated that 1 did not exhibit magnetic relaxation behavior under the external field; however, 2 exhibited zero-field single-molecule magnetic relaxation behavior with an effective energy barrier (U eff ) of 197.44 K. This is attributed to the improved anisotropy of the single ion after the normalization of the crystal structure, thus realizing the molecular magnetic switching. Moreover, magnetic dilution analysis of 2 demonstrated that the weak magnetic interaction between metal ions inhibited the occurrence of quantum tunneling of magnetization (QTM), resulting in high-performance single-molecule magnet (SMM) behavior. The reasons for the magnetic difference between these two complexes were analyzed using ab initio calculation and magneto-structural correlations. This study provides a reasonable prediction of the ideal configuration of the approximately parallelogram Dy III -based SMMs, thus offering an effective approach for synthesizing Dy 4 complexes with excellent properties.

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“…Of additional interest in the field of Ln-SMMs is the possibility of modulating the SMM properties through exchange coupling with radical ligands, providing a chemically-encoded redox switch. [5][6][7][8] However, elucidation of the sign and magnitude of this coupling is challenging in most cases, due to the large unquenched orbital angular momentum of the lanthanoid ions of interest. Building on an early study from Caneschi et al, [9] we have recently reported elucidation of the exchange coupling between an Er(III) ion and the 3,5-di-tertbutylseminquinonate (dbsq *À ) radical ligand in the complex [ErTp 2 dbsq] (Tp À = hydro-tris(1pyrazolyl)borate) in a combined experimental and computational investigation.…”

Section: Introductionmentioning

confidence: 99%

Lanthanoid Semiquinonate/Tropolonate Complexes: Redox Chemistry and Luminescence

Dunstan,

Suryadevara,

Cameron

et al. 2024

Eur J Inorg Chem

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Heteroleptic lanthanoid (Ln = Eu, Gd, Tb, Dy, Ho and Yb) complexes featuring hydro‐tris(1‐pyrazolyl)borate (Tp−) ligands combined with the bidentate O‐donor ligands tropolonate (trop−) or 3,5‐di‐tertbutylseminquinonate (dbsq●−) have been synthesized and investigated. Despite the similarity of the bidentate O‐donor trop− and dbsq●− ligands, and the lanthanoid coordination geometries, the complexes [LnTp2dbsq] (Ln‐dbsq) and [LnTp2trop] (Ln‐trop) exhibit markedly different redox and photophysical properties. The electrochemistry of Ln‐dbsq is dominated by processes associated with the readily redox‐active dbsq●− moiety. In contrast, the relative redox inactivity in Ln‐trop allows for the observation of the Eu(III) to Eu(II) reduction process. Photophysical measurements reveal no sensitized emission for the Ln‐dbsq family, while the trop− antenna ligand is able to sensitize emission in the visible range for Eu(III) and Ho(III), and in the near‐infrared for Ho(III) and Yb(III).

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Strong magnetic exchange coupling in Ln₂ metallocenes attained by the trans-coordination of a tetrazinyl radical ligand

Abstract: A combination of high-performing lanthanide metallocenes and tetrazine-based radical ligands leads to a new series of radical-bridged dinuclear lanthanide metallocenes; [(Cp*2LnIII)2(bpytz•-)][BPh4] (where Ln = Gd (1), Tb (2), Dy (3)...

Cited by 5 publications

References 67 publications

Engineering Clock Transitions in Molecular Lanthanide Complexes

Engineering Clock Transitions in Molecular Lanthanide Complexes

Structures and Single-Molecule Magnet Behavior of Dy₃ and Dy₄ Clusters Constructed by Different Dysprosium(III) Salts

Lanthanoid Semiquinonate/Tropolonate Complexes: Redox Chemistry and Luminescence

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Strong magnetic exchange coupling in Ln2 metallocenes attained by the trans-coordination of a tetrazinyl radical ligand

Abstract: A combination of high-performing lanthanide metallocenes and tetrazine-based radical ligands leads to a new series of radical-bridged dinuclear lanthanide metallocenes; [(Cp*2LnIII)2(bpytz•-)][BPh4] (where Ln = Gd (1), Tb (2), Dy (3)...

Cited by 5 publications

References 67 publications

Engineering Clock Transitions in Molecular Lanthanide Complexes

Engineering Clock Transitions in Molecular Lanthanide Complexes

Structures and Single-Molecule Magnet Behavior of Dy3 and Dy4 Clusters Constructed by Different Dysprosium(III) Salts

Lanthanoid Semiquinonate/Tropolonate Complexes: Redox Chemistry and Luminescence

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Strong magnetic exchange coupling in Ln₂ metallocenes attained by the trans-coordination of a tetrazinyl radical ligand

Structures and Single-Molecule Magnet Behavior of Dy₃ and Dy₄ Clusters Constructed by Different Dysprosium(III) Salts