Large Magnetic Anisotropy in Pentacoordinate Ni^II Complexes

Abstract

Pentacoordinate complexes in which Ni(II) is chelated by the tridentate macrocyclic ligand 1,4,7-triisopropyl-1,4,7-triazacyclononane (iPrtacn) of formula [Ni(iPrtacn)X(2)] (X=Cl, Br, NCS) have relatively large magnetic anisotropies, revealed by the large zero-field splitting (zfs) axial parameters |D| of around 15 cm(-1) measured by frequency-domain magnetic resonance spectroscopy (FDMRS) and high-field high-frequency electron paramagnetic resonance (HF-HFEPR). The spin Hamiltonian parameters for the three complexes were determined by analyzing the FDMRS spectra at different temperatures in zero applied magnetic field in an energy window between 0 and 40 cm(-1). The same parameters were determined from analysis of HF-HFEPR data measured at different frequencies (285, 380, and 475 GHz) and at 7 and 17 K. The spin Hamiltonian parameters D (axial) and E (rhombic) were calculated for the three complexes in the framework of the angular overlap model (AOM). The nature and magnitude of the magnetic anisotropy of the three complexes and the origin of the influence of the X atoms were analyzed by performing systematic calculations on model complexes.

Synthesis, crystal structure, magnetic properties and reactivity of a Ni–Ru model of NiFe hydrogenases with a pentacoordinated triplet (S=1) NiII center

“…¼ 2:07. The D value is among the highest observed for discrete nickel(II) complexes [13][14][15][16]. Since g = is lower than g ?…”

Inelastic neutron scattering studies on the odd-membered antiferromagnetic wheel Cr8Ni

“…The single-ion anisotropy of Ni(II) ions can be large, and values of up to several meV were reported. 48 We hence favor the parameters D Cr = −0.036 meV and D Ni = +1.25 meV.…”

Magnetic anisotropy in two- to eight-coordinated transition–metal complexes: Recent developments in molecular magnetism

“…Despite these high magnetic anisotropies, none of the complexes exhibited SMM behavior, even at 2 K. Indeed, in a series of penta-coordinated Ni II complexes [Ni II (iPrtacn)X 2 ] (where X = Cl (59), Br (60), or NCS (61); Fig. 20) that incorporated metal ions in almost ideal TBP ligand environments, the ZFS parameters were positive in sign, ranging between 13.93 to 16.35 cm -1 in magnitude (Table 5) [97]. The signs of these D parameters were confirmed by HF-EPR spectroscopic analysis.…”

“…Left: Molecular structure of [Co II (oda)(aterpy)](97). Color scheme: Co, blue; N, blue; O, red; C, gray.…”