Positive zero-field splitting and unexpected slow magnetic relaxation in the magneto-chemical calibrant HgCo(NCS)4

Magnetochemical standard HgCo(NCS)4 with positive zero-field splitting parameter D displays a slow magnetic relaxation strongly dependent upon the external magnetic field.

Correlating magnetic anisotropy with the subtle coordination geometry variation of a series of cobalt(ii)-sulfonamide complexes

The distortion degree from the ideal tetrahedral geometry has been correlated with the zero-field splitting parameter in a series of mononuclear cobalt(ii)-sulfonamide complexes with a CoN4 coordination environment.

Structural and magnetic properties of Co(II) complexes with tridentate ONO pincer-type ligands

Pincer type ligand 2,6-pyridinedimethanol was used as a useful tool in the preparation of the Co(II) pseudoctahedral complex together with 3,5-dinitrobenzoate counteranion. New complex of the composition [Co(pydm)2](3,5-dnbz)2(pydm = 2,6-pyridinedimethanol, and 3,5-dnbz = 3,5-dinitrobenzoate anion) has been prepared and characterized. Its XRD structure revealed pseudooctahedral {CoN2O4} chromophore around the cobalt atom with Co-N distances significantly shorter (Co-Nav = 2.038 Ǻ) in comparison to the Co-O ones (Co-Oav = 2.142 Ǻ), which was probably the reason of its relatively high zero-field splitting parameter (D/hc = 43.6 cm-1). Positive value of the D parameter causes slow relaxation process typical for Co(II) SMM behavior. The 3,5-dinitrobenzoate counteranions are strongly bonded to the [Co(pydm)2] cation via rather strong hydrogen bonds (O∙∙∙Oav = 2.568 Ǻ) forming “quasi molecular” units. Solid state structure allowed different π-π stacking interactions of neighboring “molecular” unit aromatic rings probally leading to observation of the additional relaxation mode.

Quantitative analysis of zero-field splitting parameter distributions in Gd(iii) complexes

The Zero-Field Splitting (ZFS) distributions in Gd(iii) centers are accurately analyzed, with detailed discussion of error bars, and compared to the calculations with superposition model.

Abnormal Magnetic Moment and Zero Field Splitting of Some Nickel (II) Complexes

<em>Some complexes of Ni(II) have been prepared with 2-thio-3-acetyl hydantoin (TAHN) and 2-formyl pyridine thiosemicarbazone (FPTS). On the basis of elemental analysis and molar conductivity, the complexes have been formulated as NiL₂X₂, where L = TAHN or FPTS and X = Cl^–, Br^–, NCS^–, ClO₄^–. The infrared spectra of complexes and free ligand reveal that the ligand TAHN is co-ordinated through sulphur and acetyl oxygen, while FPTS ligand co-ordinates through heterocyclic nitrogen and sulphur to Ni(II) metal ion. The magnetic moment of these complexes are found to be 3.20-3.25 B.M. The values are greater than value (2.828 B.M) corresponding to two unpaired electrons of a d⁸-system. The appearance of four absorption bands in their electronic spectra reveal, the tetragonal distortion in the octahedral symmetry of complexes. The zero field splitting parameter(D) and the other crystal field parameters like Dq_(xy), Dq_(z), Dt have been calculated. The results show that, the tetragonal distortion parameter (Dt) increases in the order of NCS^–&lt; Cl^– &lt; Br^– while the zero field splitting parameter (D) also increases in the same order for both the planer ligands.</em>

Probing the influence of molecular symmetry on the magnetic anisotropy of octahedral cobalt(ii) complexes

A series of field-induced cobalt(ii) SIMs exhibit varying axial zero-field splitting parameter D values from positive to negative with the increased distortion of the octahedral geometry.

Redetermination of Zero-Field Splitting in [Co(qu)2Br2] and [Ni(PPh3)2Cl2] Complexes

A mononuclear CoII complex, [Co(qu)2Br2], and NiII complex, [Ni(PPh3)2Cl2], (qu = quinoline, PPh3 = triphenylphosphine) have been reinvestigated. Their crystal and molecular structures are reported along with IR and UV-Vis spectra. Magnetism of both complexes has been studied by using the DC SQUID magnetometry. These complexes exhibit a moderate magnetic anisotropy expressed by zero-field splitting parameter D. The D-value is positive for both complexes with D/hc = +5.94 cm−1 and D/hc = +12.76 cm−1, that is also confirmed by ab initio calculations.

Modulation of the coordination environment: a convenient approach to tailor magnetic anisotropy in seven coordinate Co(ii) complexes

Subtle modulation of the coordination environment in seven coordinate Co(ii) complexes leads to a remarkable deviation in the axial zero field splitting parameter (D) in a predictable fashion.