A novel 2D coordination polymer based on triangular-shaped [Mn3O] units bridged by sodium ions and benzene-1,2,4,5-tetracarboxylate

a r t i c l e i n f o On the basis of triangular-shaped [Mn 3 O] secondary building units, a novel two-dimensional (2D) manganese (III) complex, [NaMn III 3 O(sao) 3 (btec) 0.5 (H 2 O) 3 ]·1.25H 2 O (1) (H 2 sao = salicylaldoxime, H 4 btec = benzene-1,2,4,5-tetracarboxylate acid), was synthesized and structurally characterized. The structure of 1 consists of 2D coordination polymer based on [Mn 3 O] units bridged by sodium ions and benzene-1,2,4,5-tetracarbox-ylate groups. Magnetic data analysis shows that antiferromagnetic couplings exist between the manganese (III) ions in [Mn 3 O] subunit of complex 1. After S. Pal' group found the first ferromagnetic oxide-centred [Mn III 3 ] triangle in 2002 [1], a series of complexes with symmetric planar central [Mn 3 O] unit have been reported in literature [2–8]. Subsequently, a new area of molecular magnetism on using the triangles as secondary building units to design and construct coordination complexes have been developed [9–12]. For instance, Xu synthesized two single-chain-magnets based on triangular-shaped [Mn 3 O] units bridged by formate and azide anions [13]. Bai constructed a new oxide-centred [Mn III 3 ] triangle with 3-(5-methyl-2-phenolate) pyrazolate ligand and connected it by acetate anions into one-dimensional system which demonstrated the coexistence of magnetization relaxation and dielectric relaxation properties [14]. Herein, we reported the synthesis, crystal structure and magnetic properties of a 2D coordination polymer based on [Mn 3 O] units bridged by sodium ions and benzene-1,2,4,5-tetracarboxylate groups, [NaMn H 4 btec=benzene-1,2,4,5-tetracarboxylate acid) [15]. Complex 1 crystallizes in monoclinic space group C2/c [16]. X-ray structural analysis reveals that complex 1 comprises a 2D framework based on Mn 3 clusters linked by btec 4− and Na + to each others. As shown in Fig. 1, the asymmetric unit contains three Mn III ions, one half btec 4− and Na + ions, three sao 2− ligands, three coordinated water molecules, and one and quarter lattice water. The core of the asymmetric unit is an analogous of the triangular [Mn 3 (μ 3-O)] 7+ unit. The coordination geometry around Mn1 is in a five-coordinated distorted square-pyramidal geometry, with the carboxyl O8 occupying the apical position. Mn2 and Mn3 are six-coordinated distorted octahedra. Mn2 is coordinated by one sao 2− ligand (N2 and O4) and the O3 donor of a second sao 2− , while Mn3 is coordinated by one sao 2− ligand (N3 and O6) …