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

Two new manganese complexes, [Mn3(L1)4(NO3)2]n (1, HL1=nicotinate N-oxide acid) and [MnL2Cl]n (2, HL2=isonicotinate N-oxide acid)], have been hydrothermally synthesized and characterized by elemental analysis, IR and single-crystal X-ray diffraction. In 1, the L1 ligands take two different coordinated modes bridging four and three MnII ions. The nitrate anions take chelating coordination modes, leading one type of the MnII ions as a 4-connected node. The whole net can be viewed as a 3, 4, 6-connected 4-nodal net with Schläfli notation {43}2{44; 62}4{46; 66; 83}. Complex 2 has a honeycomb layer mixed bridged by chlorine, N-oxide and carboxylate. The adjacent layers are linked by the phenyl ring of L2 ligand, giving a 3D framework with a {34; 54} {32;4;56;66} 4, 6-connect net. Magnetic studies indicate that 1 is an antiferromagnet with low-dimensional characteristic, in which a –J1J1J2– coupled alternating chain is predigested. Fitting the data of 1 gives the best parameters J1=−2.77, J2=−0.67 cm−1. The magnetic properties of complex 2 represent the character of the 2D honeycomb layer with the J1=−2.05 and J2=0.55 cm−1, which results in a whole antiferromagnetic state.