Optical and Paramagnetic Resonance Spectra of Some Trigonal Co(II) Chelates

Abstract

Paramagnetic resonance has been observed at 4.2°K in magnetically dilute single crystals and powders of bis[hydrotris(1-pyrazolyl)borate]Co(II) and bis[tris(1-pyrazolyl)methane]Co(II) chelate systems. The chelate structure for both types of compound has D3d symmetry, and the principal g tensor components show large axial anisotropy. In conjunction with optical data for these complexes, the results are analyzed in terms of the theory of Abragam and Pryce. In addition to the experimentally determined g values for the lowest Kramers doublet in these complexes, approximate g values and splittings are established for the other levels in the ground state manifold. Magnetically dilute powder measurements are described both for the compounds studied as single crystals and for a number of other cases where crystals could not be grown.

Trigonal antiprismatic Co(ii) single molecule magnets with large uniaxial anisotropies: importance of Raman and tunneling mechanisms

“…55 The presence of three electrons in two nearly degenerate e g orbitals is expected to lead to a large anisotropy, in this case it produces a uniaxial magnetic anisotropy as confirmed by EPR analysis 50 years ago. 56 Thus far, however, no SMMs have been reported with this geometry. We postulated that fac -tripodal ligands could enforce a trigonal antiprismatic geometry, thus we undertook a systematic study of Co( ii ) complexes equipped with tris(pyrazol-1-yl)methane (Fig.…”

An investigation of the 1H nmr isotropic shifts for some methyl-substituted bipyridine complexes with Ni(II) and Co(II)

“…Using ligand field theory, Abragam and Pryce (15) have shown that the Co(I1) ground term 4F is split by an octahedral field producing a 4Tlg ground state. Because there is strong spin-orbit coupling, this 4Tlg state is further split into six doubly degenerate levels (Kramer's doublets) (16,17) with ! 'Author to whom correspondence may be addressed.…”

Outer sphere complexes as intermediates in coordination chemistry

“…One of the most favourable molecules for studying the details of second sphere structure is bis[hydrotris(1-pyrazoyl)borato]cobalt(II) [48] the structure of which is shown in Figure 3 crystal field [49] is particularly susceptible to large g value anisotropies which lead to large dipolar chemical shifts for nuclei close to the paramagnetic metal ion. In this case gll = 8.46 and g± = 0.98 [50] which is an exceptionally large anisotropy.…”