Zero-field slow relaxation of magnetization in cobalt(ii) single-ion magnets: suppression of quantum tunneling of magnetization by tailoring the intermolecular magnetic coupling

The correlation between magnetic relaxation dynamics and the alignment of single-ion magnets (SIMs) in a crystal was investigated using four analogous cobalt(ii) complexes with unique hydrogen-bond networks. The hydrogen-bonding interactions in the crystals resulted in a relatively short intermolecular Co⋯Co distance, which led to non-zero intermolecular magnetic coupling. All the complexes with a Co⋯Co distance shorter than 6.5 Å exhibited zero-field slow magnetic relaxation as weak magnetic interactions split the ground ±M_s levels and suppressed quantum tunneling of magnetization (QTM). In particular, antiferromagnetically coupled one-dimensional chain SIM networks effectively suppressed QTM when the two intrachain Co⋯Co distances were non-equivalent. However, when the two distances in a chain were equivalent and each molecular symmetry axis aligned parallell within the chain, QTM suppression was insufficient because magnetic coupling from the adjacent molecules was virtually cancelled. Partial substitution of the Co^II ion with the diamagnetic Zn^II ion up to 33% for this complex resulted in complete QTM suppression in the absence of an external field. These results show that the manipulation of intermolecular distances and alignments is effective for suppressing undesired QTM events in SIMs.

Quenching of quantum tunneling of magnetization was observed in a tetrahedral cobalt(ii) complex with 1-D chain hydrogen-bond networks by partially substituting the Co^II ion with the Zn^II ion, up to 33%.

Detailed magnetic analysis and successful deep-neural-network-based conformational prediction for [VO(dmso)5][BPh4]2

The conformer in the crystal was successfully predicted by a deep neural network method.

Magnetic and liquid-crystalline properties of chlorido- and cyanato-bridged chain complexes of mixed-valent dinuclear ruthenium(ii,iii) 3,4,5-trialkoxybenzoates

A series of cyanato-bridged chain complexes of mixed-valent dinuclear ruthenium(ii,iii) 3,4,5-trialkoxybenzoates, [Ru₂{3,4,5-(n-C_mH_2m+1O)₃C₆H₂CO₂}₄(X)]_n (X = OCN, Cl; m = 2–18), were synthesized.

Hydrogen-bonding interactions and magnetic relaxation dynamics in tetracoordinated cobalt(ii) single-ion magnets

Zero field slow magnetic relaxation was observed in two cobalt(ii) complexes with 1-D chain hydrogen-bonded structures.

Field-induced single-molecule magnet behavior in ideal trigonal antiprismatic cobalt(ii) complexes: precise geometrical control by a hydrogen-bonded rigid metalloligand

A new cobalt(ii) complex bearing a pair of cobalt(iii) tris-chelate complexes as metalloligands was prepared. The CoII ion possesses an ideal trigonal antiprismatic geometry because of the intermolecular hydrogen-bonds between the metalloligands via counter anions. This complex exhibits slow magnetic relaxation under a dc field reminiscent of a single-molecule magnet behavior.

Magnetic Properties of a Dinuclear Nickel(II) Complex with 2,6-Bis[(2-hydroxyethyl)methylaminomethyl]-4-methylphenolate

Magnetic properties of dinuclear nickel(II) complex [Ni₂(sym-hmp)₂](BPh₄)₂·3.5DMF·0.5(2-PrOH) (1), where (sym-hmp)^- is 2,6-bis[(2-hydroxyethyl)methylaminomethyl]-4-methylphenolate anion and DMF indicates dimethylformamide, were investigated using high-frequency and -field electron paramagnetic resonance (HFEPR). To magnetically characterize the mononuclear nickel(II) species forming the dimer, its two dinuclear zinc(II) analogues, [Zn₂(sym-hmp)₂](BPh₄)₂·3.5DMF·0.5(2-PrOH) (2) and [Zn₂(sym-hmp)₂](BPh₄)₂·2acetone·2H₂O (2'), were prepared. One of them (2') was structurally characterized by X-ray diffractometry and doped with 5% mol nickel(II) ions to prepare a mixed crystal 3. From the HFEPR results on complex 1 obtained at 40 K, the spin Hamiltonian parameters of the first excited spin state (S = 1) of the dimer were accurately determined as |D₁| = 9.99(2) cm^-1, |E₁| = 1.62(1) cm^-1, and g₁ = [2.25(1), 2.19(2), 2.27(2)], and for the second excited spin state (S = 2) at 150 K estimated as |D₂| ≈ 3.5 cm^-1. From these numbers, the single-ion zero-field splitting (ZFS) parameter of the Ni(II) ions forming the dimer was estimated as |D_Ni| ≈ 10-10.5 cm^-1. The HFEPR spectra of 3 yielded directly the single-ion parameters for D_Ni = +10.1 cm^-1, |E_Ni| = 3.1 cm^-1, and g_iso = 2.2. On the basis of the HFEPR results, the previously obtained magnetic data (Sakiyama, H.; Tone, K.; Yamasaki, M.; Mikuriya, M. Inorg. Chim. Acta 2011, 365, 183) were reanalyzed, and the isotropic interaction parameter between the Ni(II) ions was determined as J = -70 cm^-1 (H_ex = -J S_A·S_B). Finally, density functional theory calculations yielded the J value of -90 cm^-1 in a qualitative agreement with the experiment.

Magneto-structural correlation of hexakis-dmso cobalt(ii) complex

The magnetostructural correlation of the hexakis-dmso cobalt(ii) complex, [Co(dmso)₆](BPh₄)₂ (dmso: dimethylsulfoxide), was investigated by single-crystal X-ray diffraction study and magnetic measurements.

Nickel(II) complex with 1,4,7-tris(2-aminoethyl)-1,4,7-triazacyclononane‡

A nickel(II) complex, [Ni(taetacn)](ClO