Impact of coordinated anions on field-induced slow magnetic relaxation in mononuclear Cobalt(II) compounds

Zheng Tang; Qiman Che; Yingying Zhang; Junfei Fan; Shuang Jin; Xiao Peng Sun; Pengtao Ma; Zi Shuo Yao; Jingping Wang; Jingyang Niu; Jun Tao

doi:10.1016/j.molstruc.2025.145142

Impact of coordinated anions on field-induced slow magnetic relaxation in mononuclear Cobalt(II) compounds

Zheng Tang
, Qiman Che
, Yingying Zhang
, Junfei Fan
, Shuang Jin
, Xiao Peng Sun^*
, Pengtao Ma
, Zi Shuo Yao
, Jingping Wang
, Jingyang Niu
, Jun Tao

^*Corresponding author for this work

Research output: Contribution to journal › Article › peer-review

Abstract

Contrasting coordinated ligands in isostructural compounds provide a powerful strategy for tuning slow magnetic relaxation. Herein, we report two new mononuclear Co(II) compounds, [Co(H₂L)Cl₂]·0.5H₂O (1, H₂L = 6, 6’-bis(benzimidazole-2-yl)-2, 2’-bipyridine) and [Co(H₂L)(NCS)₂] (2), featuring the identical equatorial ligand but differing in axial ligands. Molecular structural analysis revealed the Co(II) center in 1 adopted a hexacoordinate geometry, coordinated by four N atoms from H₂L ligand in the equatorial plane and two Cl⁻ anions in the axial positions. In contrast, the axial sites in compound 2 were occupied by two NCS⁻ anions. The varying axial anionic ligands gave rise to an elongated {CoN₄Cl₂} octahedron in 1 and a compressed {CoN₆} octahedron in 2. Alternating-current magnetic susceptibility measurements confirmed that both compounds were field-induced single-ion magnets (SIMs), exhibiting different effective energy barriers. Fitting with the temperature dependence of the relaxation time expression indicated their relaxation dynamics were primarily governed by Orbach, Direct and Raman processes. This work underscores the crucial role of coordinated ligands in design of Co(II)-based SIMs.

Original language	English
Article number	145142
Journal	Journal of Molecular Structure
Volume	1356
DOIs	https://doi.org/10.1016/j.molstruc.2025.145142
Publication status	Published - 5 Apr 2026
Externally published	Yes

Keywords

Axial ligands
Cobalt(II) compounds
Coordinated anions
Single-ion magnets

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10.1016/j.molstruc.2025.145142

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title = "Impact of coordinated anions on field-induced slow magnetic relaxation in mononuclear Cobalt(II) compounds",

abstract = "Contrasting coordinated ligands in isostructural compounds provide a powerful strategy for tuning slow magnetic relaxation. Herein, we report two new mononuclear Co(II) compounds, [Co(H2L)Cl2]·0.5H2O (1, H2L = 6, 6{\textquoteright}-bis(benzimidazole-2-yl)-2, 2{\textquoteright}-bipyridine) and [Co(H2L)(NCS)2] (2), featuring the identical equatorial ligand but differing in axial ligands. Molecular structural analysis revealed the Co(II) center in 1 adopted a hexacoordinate geometry, coordinated by four N atoms from H2L ligand in the equatorial plane and two Cl− anions in the axial positions. In contrast, the axial sites in compound 2 were occupied by two NCS− anions. The varying axial anionic ligands gave rise to an elongated \{CoN4Cl2\} octahedron in 1 and a compressed \{CoN6\} octahedron in 2. Alternating-current magnetic susceptibility measurements confirmed that both compounds were field-induced single-ion magnets (SIMs), exhibiting different effective energy barriers. Fitting with the temperature dependence of the relaxation time expression indicated their relaxation dynamics were primarily governed by Orbach, Direct and Raman processes. This work underscores the crucial role of coordinated ligands in design of Co(II)-based SIMs.",

keywords = "Axial ligands, Cobalt(II) compounds, Coordinated anions, Single-ion magnets",

author = "Zheng Tang and Qiman Che and Yingying Zhang and Junfei Fan and Shuang Jin and Sun, \{Xiao Peng\} and Pengtao Ma and Yao, \{Zi Shuo\} and Jingping Wang and Jingyang Niu and Jun Tao",

note = "Publisher Copyright: {\textcopyright} 2025 Elsevier B.V.",

year = "2026",

month = apr,

day = "5",

doi = "10.1016/j.molstruc.2025.145142",

language = "English",

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journal = "Journal of Molecular Structure",

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TY - JOUR

T1 - Impact of coordinated anions on field-induced slow magnetic relaxation in mononuclear Cobalt(II) compounds

AU - Tang, Zheng

AU - Che, Qiman

AU - Zhang, Yingying

AU - Fan, Junfei

AU - Jin, Shuang

AU - Sun, Xiao Peng

AU - Ma, Pengtao

AU - Yao, Zi Shuo

AU - Wang, Jingping

AU - Niu, Jingyang

AU - Tao, Jun

PY - 2026/4/5

Y1 - 2026/4/5

N2 - Contrasting coordinated ligands in isostructural compounds provide a powerful strategy for tuning slow magnetic relaxation. Herein, we report two new mononuclear Co(II) compounds, [Co(H2L)Cl2]·0.5H2O (1, H2L = 6, 6’-bis(benzimidazole-2-yl)-2, 2’-bipyridine) and [Co(H2L)(NCS)2] (2), featuring the identical equatorial ligand but differing in axial ligands. Molecular structural analysis revealed the Co(II) center in 1 adopted a hexacoordinate geometry, coordinated by four N atoms from H2L ligand in the equatorial plane and two Cl− anions in the axial positions. In contrast, the axial sites in compound 2 were occupied by two NCS− anions. The varying axial anionic ligands gave rise to an elongated {CoN4Cl2} octahedron in 1 and a compressed {CoN6} octahedron in 2. Alternating-current magnetic susceptibility measurements confirmed that both compounds were field-induced single-ion magnets (SIMs), exhibiting different effective energy barriers. Fitting with the temperature dependence of the relaxation time expression indicated their relaxation dynamics were primarily governed by Orbach, Direct and Raman processes. This work underscores the crucial role of coordinated ligands in design of Co(II)-based SIMs.

AB - Contrasting coordinated ligands in isostructural compounds provide a powerful strategy for tuning slow magnetic relaxation. Herein, we report two new mononuclear Co(II) compounds, [Co(H2L)Cl2]·0.5H2O (1, H2L = 6, 6’-bis(benzimidazole-2-yl)-2, 2’-bipyridine) and [Co(H2L)(NCS)2] (2), featuring the identical equatorial ligand but differing in axial ligands. Molecular structural analysis revealed the Co(II) center in 1 adopted a hexacoordinate geometry, coordinated by four N atoms from H2L ligand in the equatorial plane and two Cl− anions in the axial positions. In contrast, the axial sites in compound 2 were occupied by two NCS− anions. The varying axial anionic ligands gave rise to an elongated {CoN4Cl2} octahedron in 1 and a compressed {CoN6} octahedron in 2. Alternating-current magnetic susceptibility measurements confirmed that both compounds were field-induced single-ion magnets (SIMs), exhibiting different effective energy barriers. Fitting with the temperature dependence of the relaxation time expression indicated their relaxation dynamics were primarily governed by Orbach, Direct and Raman processes. This work underscores the crucial role of coordinated ligands in design of Co(II)-based SIMs.

KW - Axial ligands

KW - Cobalt(II) compounds

KW - Coordinated anions

KW - Single-ion magnets

UR - https://www.scopus.com/pages/publications/105025678923

U2 - 10.1016/j.molstruc.2025.145142

DO - 10.1016/j.molstruc.2025.145142

M3 - Article

AN - SCOPUS:105025678923

SN - 0022-2860

VL - 1356

JO - Journal of Molecular Structure

JF - Journal of Molecular Structure

M1 - 145142

ER -

Impact of coordinated anions on field-induced slow magnetic relaxation in mononuclear Cobalt(II) compounds

Abstract

Keywords

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