Axial Ligand Field in D4d Coordination Symmetry: Magnetic Relaxation of Dy SMMs Perturbed by Counteranions

A series of mononuclear Dy-III complexes with the general formula [DyLz(2)(salicylaldehyde)(2)].X.solvent (Lz = 6-pyridin-2-yl[1,3,5]triazine-2,4-diamine; X = OH-(1 center dot OH), CI- (2 center dot C1), Br- (3 center dot Br)) have been synthesized using mixed salicylaldehyde/pyridinyl-triazine ligands and discriminative counteranions. The Dy-III ion in these three complexes resides in a similar D-4d coordination geometry with counteranions perturbing the coordination environment and bond lengths and angles in the lattice. Magnetostructural studies reveal that the asymmetric distribution of salicylaldehyde/pyridinyl-triazine ligands and the presence of discriminative counter anions result in the coexistence of large anisotropy and quantum tunneling of magnetization. The magnetic anisotropy is dominated by the axial ligand field with short Dy-O-sali distances and large