Understanding the unceasing evolution of Co(II) based single-ion magnets

Sahu, Pradip Kumar; Kharel, Ranjan; Shome, Shraoshee; Goswami, Soumyabrata; Konar, Sanjit

doi:10.1016/j.ccr.2022.214871

Cited by 43 publications

(59 citation statements)

References 124 publications

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“…Having developed over decades, thousands of SMMs have been synthesized and characterized to display a variety of magnetic complexes with distinct barrier ( U eff ) and magnetic blocking temperatures ( T B ) . One of the milestones in this field is that a mononuclear Fe II complex was observed to display slow magnetic relaxation in 2010 by Long et al, which greatly prompted the search of new monometallic transition-metal-based SMMs (also termed single-ion magnets, SIMs) . With the characterization of a high-performance organometallic Er(III) SIM reported by Gao and co-workers, the design principles from multinuclear SMMs to SIMs were basically established, and the field of SIMs has then entered a stage of rapid development.…”

Section: Introductionmentioning

confidence: 99%

“…2 One of the milestones in this field is that a mononuclear Fe II complex was observed to display slow magnetic relaxation in 2010 by Long et al, 3 which greatly prompted the search of new monometallic transitionmetal-based SMMs (also termed single-ion magnets, SIMs). 4 With the characterization of a high-performance organometallic Er(III) SIM reported by Gao and co-workers, 5 the design principles from multinuclear SMMs to SIMs were basically established, and the field of SIMs has then entered a stage of rapid development. To date, the very best SIM systems were found to be related to the low-coordinate transition-metal ions and organometallic lanthanide complexes within a particular coordination geometry, which can greatly improve the limit of magnetic anisotropy.…”

Section: ■ Introductionmentioning

confidence: 99%

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Incorporating Highly Anisotropic Four-Coordinate Co(II) Ions within One-Dimensional Coordination Chains

Long

Yang

Moorthy

et al. 2023

Crystal Growth & Design

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Low-coordinate metallic ions have been well recognized for constructing good-performance single ion magnets (SIMs) due to their enhanced magnetic anisotropy; however, the incorporation of such specific ions into coordination polymers is still challenging. Here, we reported two new Co II coordination polymers, namely [Co(pdms)(bpe)] n (1) and {[Co(pdmsSingle crystal X-ray diffraction experiments indicated that the Co II centers in both 1 and 2 display a distorted tetrahedral geometry with quasi C 2v symmetry and are linked into a one-dimensional (1D) zig-zag chain via the ditopic bridging ligand of bpe in 1 while a ribbon chain via the tetradentate linker of tpb in 2. Magnetic studies revealed the easy-axis magnetic anisotropy of the Co II ions with different zerofield splitting D of −19 cm −1 (1) and −33 cm −1 (2), likely due to the distinct changes in the N py −Co−N py bite angles (100.20°(1) vs. 93.90°(2)). Moreover, slow magnetic relaxation proceeded via different relaxation mechanisms under applied dc fields was observed, giving an effective energy barrier (U eff ) of 69.6 K for 1 and 76.6 K for 2, respectively. The ab initio calculations on both the polymers further confirmed the sign and magnitude of the ZFS parameters and nicely reproduced the experimental results. Our study demonstrated a great potential for applying the well-studied and highly anisotropic 4-coordinate metal ions within a coordination polymer, opening a viable means to tuning magnetic anisotropy via topological control.

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Section: Introductionmentioning

confidence: 99%

Section: ■ Introductionmentioning

confidence: 99%

Incorporating Highly Anisotropic Four-Coordinate Co(II) Ions within One-Dimensional Coordination Chains

Long

Yang

Moorthy

et al. 2023

Crystal Growth & Design

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“…Recent review collects the data about the D -parameter in the Co(II) complexes from two- to hepta-coordination . It can be seen that the data vary in an unexpected range from very negative to very positive.…”

Section: Resultsmentioning

confidence: 99%

“…Recent review collects the data about the D-parameter in the Co(II) complexes from two-to hepta-coordination. 19 It can be seen that the data vary in an unexpected range from very negative to very positive. They were obtained in a nonsystematic way using different experiments and different software.…”

Section: Resultsmentioning

confidence: 99%

Possible Violation of the Spin-Hamiltonian Concept in Interpreting the Zero-Field Splitting

Boča

Titiš

2023

J. Phys. Chem. A

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The majority of experimental data in electron spin resonance and molecular magnetism are interpreted in terms of the spin-Hamiltonian (SH) formalism. However, this is an approximate theory that requires a proper testing. In the older variant, the multielectron terms are used as a basis in which the D-tensor components are evaluated by employing the second-order perturbation theory (PT) for nondegenerate states; here, the spin–orbit interaction expressed via the spin–orbit splitting parameter λ serves for the perturbation. The model space is restricted only to the fictitious spin functions |S, M⟩. In the case of the orbital (quasi) degeneracy of the ground term, the PT tends to diverge and the subtracted D, E, and g parameters are false. In the second variant working in the “complete active space” (CAS), the spin–orbit coupling operator is involved by the variation method resulting in the spin–orbit multiplets (energies and eigenvectors) The multiplets can be evaluated either by applying ab initio CASSCF + NEVPT2 + SOC calculations or by using semiempirical generalized crystal-field theory (with the one-electron SOC operator depending upon ξ). The resulting states can be projected onto the subspace of the spin-only kets in the way that the eigenvalues stay invariant. Such an effective Hamiltonian matrix can be reconstructed using six independent components of the symmetric D-tensor from which the D and E values are obtained by solving linear equations. The eigenvectors of the spin–orbit multiplets in the CAS allow determining the dominating composition of the spin projectioncumulative weights of |±M⟩. These are conceptually different from those generated by the SH alone. It is shown that in some cases, the SH theory works satisfactorily for a series of transition-metal complexes; however, sometimes it fails. The ab initio calculations on the SH parameters are compared with the approximate generalized crystal-field theory conducted at the experimental geometry of the chromophore. In total, 12 metal complexes have been analyzed. One of the criteria that assesses the validity of SH is the projection norm N for spin multiplets (this has not to be far from 1). Another criterion is the gap in the spectrum of the spin–orbit multiplets that separates the hypothetical (fictitious) spin-only manifold from the rest of the states.

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“…21 Our results are interesting in the confrontations with a dataset about the sign and values of the D-parameter in Co(II) and Fe(I) complexes as reported elsewhere. [22][23][24][25][26][27]…”

Section: Introductionmentioning

confidence: 99%

Easy-axis magnetic anisotropy in tetragonally elongated cobalt(ii) complexes beyond the spin-Hamiltonian formalism

et al. 2023

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Understanding the unceasing evolution of Co(II) based single-ion magnets

Cited by 43 publications

References 124 publications

Incorporating Highly Anisotropic Four-Coordinate Co(II) Ions within One-Dimensional Coordination Chains

Incorporating Highly Anisotropic Four-Coordinate Co(II) Ions within One-Dimensional Coordination Chains

Possible Violation of the Spin-Hamiltonian Concept in Interpreting the Zero-Field Splitting

Easy-axis magnetic anisotropy in tetragonally elongated cobalt(ii) complexes beyond the spin-Hamiltonian formalism

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