Diastereoisomerism and SIM Behavior in Mononuclear Co(II) Systems Based on Mepirizole

Two diastereoisomers of bis(mepirizole)bis(isothiocyanato-K,N)cobalt(II) (1 and 2) have been isolated from the reaction of cobalt(II) thiocyanate and meperizole depending on the crystallisation solvent (ethanol, 1; acetonitrile, 2). In both crystal structures, the Co(II) ions exhibit distorted octahedral [CoN₄N’₂] environment. The analysis of the packing frameworks shows a cooperative relationship between non-classical Hbonds C(sp³)H···X (X = N, O, S, pi) and pi-hole bonds, which control the arrangement of the supramolecular 3D networks. The values of the shortest intermolecular metal-metal separation are 8.584(2) in 1 and 8.249(1) in 2. Both diatereoisomers exhibit magnetic behavior typical of mononuclear Co(II) systems with significant zero-field splitting (ZFS) values, D being 75.8(1) and 52.9(2) cm-1 for 1 and 2, respectively. Q-band EPR studies confirm the positive value for the D parameters for both compounds. Alternating current dynamic susceptibility measurements show that 1 and 2 exhibit field-induced slow relaxation of the magnetization, which is reminiscent of single-ion magnet (SIM) behavior.