Field-Induced Single-Ion-Magnetic Behavior of Octahedral CoII in a Two-Dimensional Coordination Polymer

Two 2D coordination polymers have been synthesized by employing V-shaped flexible terpyridine-based ligand L [L = 4'-(4-methoxyphenyl)-4,2':6',4''-terpyridine] as linker and M-II (M = Co-II, Fe-II) as nodes. Structural analysis of both complexes revealed the formation of a rare [4+ 4] metallocyclic unit. The extension of these cyclic units into two dimensions gives rise to an interdigitated 2D sheet structure in which the methoxy group of the ligand is oriented above and below the sheet to form crests and troughs. Detailed dc and ac magnetic susceptibility measurements revealed the field-induced slow magnetic relaxation behavior of the magnetically isolated six-coordinate Co-II center with easy-plane magnetic anisotropy. The effective energy barrier (U-eff) was found to be 36.9 K, which is the highest value reported so far for 2D Co-II-based single-ion magnets.