Paramagnetic anisotropy in cobalt(II) Schiff-base complexes. X-Ray crystal structure and electron spin resonance of NN′-ethylenebis-(acetylacetoneiminato)cobalt(II)-doped NN′-ethylenebis(acetylacetone-iminato)nickel(II)

Abstract

The e m . study of a single crystal of NN'-ethylenebis(acetylacetoneiminato)cobalt(ii)-doped NN'-ethylenebis-(acetylacetoneiminato)nickel(ii), [Co(acacen)] and [Ni(acacen)], is reported ; determination of the ground state of the cobalt complex was attempted. [Ni(acacen)] Is isomorphous with [Co(acacen)] as shown by a single-crystal structural determination : the doped crystals are orthorhombic. space group Pna2,. Z = 4, a = 12.1 8(1), b = 10.28(1), and c = 10.37(1). The equatorial principal axes of the g tensor were found to be almost parallel with the cobalt-ligand bond, rather than between these bonds, as expected.

On the electronic structure of N,N′-ethylenebis(acetylacetonatiminato)Co(II), Co(II)acacen

“…The orientations of the g and A principal axes system with respect to the molecular frame are consistent with those found in similar compounds [9,28]. Only for Coacacen in anhydrous Niacacen have Cariati et al found that gxx bisects the molecular x,y axes [17]. Daul et al have pointed out, however, that after a detailed reconsideration of these data an assignment of the gxx axis parallel to the twofold molecular axis x is more plausible [9].…”

“…In the E.P.R./ENDOR measurements two magnetically inequivalent sites were observed for Coacacen in Niacacen'l/2H20 in contrast to the anhydrous form of Niacacen, where four inequivalent sites have been found [17]. The spectra of the two sites of the hemihydrate crystal coincide only for the rotation around axis I (cf.…”

“…This indicates that the molecular symmetry is C2(x ) rather than C2~(x), although the deviauons from Car are quite small. C2(x ) is the idealized molecular symmetry if we consider the non-planarity of the ethylenediimine i~ridge [17]. The orientation of the M z2, A33(Q2 z,Q33) principal axes which include an angle of -l 2 ___ 3 ~ (-10 +_ 5 ~ with the corresponding g-axes might be influenced by the lattice, possibly by the crystal water.…”

The calculation of ESR parameters by density functional theory: the g- and A-tensors of Co(acacen)

“…The geometry of the complex has been adopted from X-ray crystallographic data determined by Cariati et al [26]. Since the deviation from C 2v symmetry is not significant we have chosen to impose this symmetry in our calculations.…”

Accurate predictions of the EPR parameters in planar cobalt(II) complexes by hybrid density functional theory

“…To avoid gauge dependence of the g-values upon the origin chosen for the magnetic field if one uses a finite basis set, the gauge including atomic orbitals (GIAO) [42,43] method was used. The experimental geometries based on X-ray crystallographic data determined by Cariati and coworkers [44] were adopted. Calculations were done for four Co(II) complexes that are shown in Fig.…”