Limiting negative zero-field splitting in tetrakis(imidazole)bis(acetato) nickel(II) complex

Magnetic properties of bis(acetato-O)tetrakis(imidazole-N3)nickel(II) have been investigated by low-temperature magnetic susceptibility as well as high-field magnetisation and subjected to theoretical analysis. A simultaneous fitting of susceptibility and magnetisation gave the following set of magnetic parameters: gz=2.181, gx=2.039, and D/hc=−22.3 cm−1. Thanks to the magnetisation measurements the sign of the axial zero-field splitting parameter is fixed unambiguously. The negative value of the D-parameter, unexpected for the geometry of an elongated tetragonal bipyramid, is understandable by introducing different orbital reduction factors for axial (acetate) and equatorial (imidazole) ligands.