Field induced single ion magnet behavior in Co II complexes in a distorted square pyramidal geometry.

We report three Co II -based complexes with the general formula [Co II (L)(X) 2 ] by changing the halide/pseudo-halide ions [X = NCSe (1SeCN); Cl (2Cl) and Br (3Br)]. The obtained τ 5 and CShM values confirm a distorted square pyramidal geometry around the Co II ion in all these complexes. In these three complexes, the central Co II ion is situated above the basal plane of the square pyramidal geometry. The extent of distortion from the ideal SPY-5 geometry differs upon changing the coordinating halide/pseudo-halide ion in these complexes. This essentially results in the alteration of the anisotropic parameter D and hence impacts the magnetic properties in these complexes. This phenomenon has been corroborated with the aid of theoretical investigations. All these complexes display field-induced SIM behaviour with magnetic relaxation occurring through a combination of processes depending on the applied dc magnetic field values and dilution.