Structure and Magnetocaloric Effect of Two Kinds of Ln-MnII Heterometallic Coordination Polymers Produced by Fractional Crystallization.

Two series of Ln-Mn^II heterometallic coordination polymers (HCPs), [Ln₈Mn₃(µ₃-OH)₈(IN)₁₄Cl₆(H₂O)₁₆] _n(OH)_{2 n} ·5 nDMF ·8 nH₂O {Ln = Gd ( 1); Ln = Dy ( 2)} and [Ln₂Mn(IN)₆Cl₂(H₂O)₄] _n ·2 nDMF {Ln = Gd ( 3); Ln = Dy ( 4), IN = isonicotinic cation}, were synthesized by using fractional crystallization and structurally characterized. Polymers 1 and 2 are isostructural and form a 2D double layer of [Ln₄(µ₃-OH)₄] cubane and Mn(IN)₄Cl₂ units, whereas 3 and 4 are isomorphic and form a four-connected cds-type 3D framework assembled from paddle-wheel binuclear Ln₂(COO)₄ units and planar Mn(IN)₄Cl₂ units. Polymers 1- 4 exhibited large magnetic entropy changes of 42.0, 16.7, 31.5, and 16.6 J kg^-1 K^-1, respectively (Δ H = 7 T). In addition, compounds 2 and 4 displayed field-induced slow magnetic relaxation behavior. [ABSTRACT FROM AUTHOR]