“…Thus, slow magnetic relaxation in mononuclear complexes with S = 1/2 has been reported for such 3d ions as V IV , 11-13 Mn IV , 14 Fe III , 15 Ni I , 16,17 Ni III , 18 and Co II , [19][20][21] which are characterized by strong spin-orbit coupling associated with the unquenched orbital angular momentum in the ground states. At the same time, the majority of 3d metal complexes with S = 1/2 demonstrating slow magnetic relaxation are characterized by low stability in the presence of atmospheric oxygen and moisture, which is related to the unusual coordination and/or oxidation state of the central ions.Interestingly, the slow magnetic relaxation is also observed for Cu(II)-complexes, 13,[22][23][24][25][26][27][28][29] in which the ground state does not carry any unquenched orbital momentum and thus the spin-orbit…”