New divalent manganese complex with pyridine carboxylate N-oxide ligand: Synthesis, structure and magnetic properties

Abstract

Two new manganese complexes, [Mn 3( L 1 ) 4(NO 3) 2] n ( 1, H L 1 =nicotinate N-oxide acid) and [Mn L 2 Cl] n ( 2, H L 2 =isonicotinate N-oxide acid)], have been hydrothermally synthesized and characterized by elemental analysis, IR and single-crystal X-ray diffraction. In 1, the L 1 ligands take two different coordinated modes bridging four and three Mn II ions. The nitrate anions take chelating coordination modes, leading one type of the Mn II ions as a 4-connected node. The whole net can be viewed as a 3, 4, 6-connected 4-nodal net with Schläfli notation {4 3}2{4 4; 6 2}4{4 6; 6 6; 8 3}. Complex 2 has a honeycomb layer mixed bridged by chlorine, N-oxide and carboxylate. The adjacent layers are linked by the phenyl ring of L 2 ligand, giving a 3D framework with a {3 4; 5 4} {3 2;4;5 6;6 6} 4, 6-connect net. Magnetic studies indicate that 1 is an antiferromagnet with low-dimensional characteristic, in which a – J 1 J 1 J 2– coupled alternating chain is predigested. Fitting the data of 1 gives the best parameters J 1=−2.77, J 2=−0.67 cm −1. The magnetic properties of complex 2 represent the character of the 2D honeycomb layer with the J 1=−2.05 and J 2 =0.55 cm −1, which results in a whole antiferromagnetic state.