Syntheses, structures, and magnetic properties of a series of Mn–M–Mn trinuclear complexes with different spin configurations

Abstract

A series of trinuclear complexes, [Mn^II₂Y^III(L)₂(HL)₂(NO₃)₃][Y^III(NO₃)₅]·7H₂O (1′), [Mn^II₂Gd^III(HL)₄(NO₃)₄]₂[Mn^II₂Gd^III(L)(HL)₃(NO₃)₄][Gd^III(NO₃)₅]₄·2(o-Xy)·12H₂O (2′) and [Mn^II₃(L)(HL)₂(NO₃)₄](NO₃)·1.25(p-Xy) (3′), were synthesized using a β-diketone ligand HL (HL = 1,3-bis(pyridin-2-yl)propane-1,3-dione). X-ray structural analyses revealed that each complex has a trinuclear core with an Mn(II)–M–Mn(II) arrangement (M = Y^III (1), Gd^III (2), and Mn^II (3)). In 1′ with a diamagnetic Y(III) ion, negligible antiferromagnetic interactions between terminal Mn(II) ions are operative. On the other hand, 2′ shows ferromagnetic interactions between Mn(II) and Gd(III) ions, affording a spin ground state of S_T = 17/2. The homometallic Mn(II)₃ complex of 3′ has an S_T = 5/2 spin ground state resulting from the antiferromagnetic interactions between neighboring Mn(II) ions. The maximum magnetic entropy change (−ΔS_m) of 1′–3′ was estimated to be 12.3, 24.8, and 8.0 J kg⁻¹ K⁻¹, respectively.