Cobalt–Lanthanide Coordination Polymers Constructed with Metalloligands: A Ferromagnetic Coupled Quasi‐1D Dy 3+ Chain Showing Slow Relaxation

Four types of cobalt–lanthanide heterometallic compounds based on metalloligand Co(2,5‐pydc) 3 3− (2,5‐H 2 pydc=pyridine‐2,5‐dicarboxylate acid), [Ln 2 Co 2 (2,5‐pydc) 6 (H 2 O) 4 ] n ⋅ 2 n  H 2 O ( 1 ) (Ln=Tb, Dy for 1 a , 1 b respectively), [Tb 2 Co 2 (2,5‐pydc) 6 (H 2 O) 4 ] n ⋅ 3 n  H 2 O ( 2 ), [Tb 2 Co 2 (2,5‐pydc) 6 (H 2 O) 9 ] n ⋅ 4 n  H 2 O ( 3 ), and [LaCo(2,5‐pydc) 3 (H 2 O) 2 ] n ⋅ 2 n  H 2 O ( 4 ) have been synthesized. Compound 1 has a layer structure with well‐isolated carboxylate‐bridged Ln 3+ chains, compound 2 is a three‐dimensional (3D) porous network with Tb 3+ chains that are also well isolated and carboxylate bridged, 3 is a layer structure based on dinuclear units, and 4 is a 3D network with boron nitride (BN) topology. DC magnetic studies reveal ferromagnetic coupling in all the carboxylate‐bridged Ln 3+ chains in 1 a , 1 b , and 2 . Compared to the silence of the out‐of‐phase ac susceptibility of 2 , above 1.9 K the magnetic relaxation behavior of both 1 a and 1 b is slow like that of a single‐chain magnet.