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

A series of trinuclear complexes, [MnII2Y III (L) 2 (HL) 2 (NO 3 ) 3 ][Y III (NO 3 ) 5 ]·7H 2 O (1'), [MnII2Gd III (HL) 4 (NO 3 ) 4 ] 2 [MnII2Gd III (L)(HL) 3 (NO 3 ) 4 ][Gd III (NO 3 ) 5 ] 4 ·2( o -Xy)·12H 2 O (2') and [MnII3(L)(HL) 2 (NO 3 ) 4 ](NO 3 )·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 (-Δ S m ) of 1'-3' was estimated to be 12.3, 24.8, and 8.0 J kg -1 K -1 , respectively.