Magnetic anisotropy and structural flexibility in the field-induced single ion magnets [Co{(OPPh)(EPPh)N}], E = S, Se, explored by experimental and computational methods

During the last few years, a large number of mononuclear Co( ii ) complexes of various coordination geometries have been explored as potential single ion magnets (SIMs). In the work presented herein, the Co( ii ) S = 3/2 tetrahedral [Co{(OPPh 2 )(EPPh 2 )N} 2 ], E = S, Se, complexes (abbreviated as CoO 2 E 2 ), bearing chalcogenated mixed donor-atom imidodiphosphinato ligands, were studied by both experimental and computational techniques. Specifically, direct current (DC) magnetometry provided estimations of their zero-field splitting (zfs) axial ( D ) and rhombic ( E ) parameter values, which were more accurately determined by a combination of far-infrared magnetic spectroscopy and high-frequency and -field EPR spectroscopy studies. The latter combination of techniques was also implemented for the S = 3/2 tetrahedral [Co{(EP i Pr 2 ) 2 N} 2 ], E = S, Se, complexes, confirming the previously determined magnitude of their zfs parameters. For both pairs of complexes (E = S, Se), it is concluded that the identity of the E donor atom does not significantly affect their zfs parameters. High-resolution multifrequency EPR studies of CoO 2 E 2 provided evidence of multiple conformations, which are more clearly observed for CoO 2 Se 2 , in agreement with the structural disorder previously established for this complex by X-ray crystallography. The CoO 2 E 2 complexes were shown to be field-induced SIMs, i.e. , they exhibit slow relaxation of magnetization in the presence of an external DC magnetic field. Advanced quantum-chemical calculations on CoO 2 E 2 provided additional insight into their electronic and structural properties. The electronic and magnetic properties of the tetrahedral Co( ii ) complexes [Co{(OPPh 2 )(EPPh 2 )N} 2 ], E = S, Se, are explored by experimental and computational methods, and discussed with respect to their structural features.