Abstract: On the basis of triangular-shaped [Mn3O] secondary building units, a novel two-dimensional (2D) manganese(III) complex, [NaMnIII 3O(sao)3(btec)0.5(H2O)3]·1.25H2O (1) (H2sao=salicylaldoxime, H4btec=benzene-1,2,4,5-tetracarboxylate acid), was synthesized and structurally characterized. The structure of 1 consists of 2D coordination polymer based on [Mn3O] units bridged by sodium ions and benzene-1,2,4,5-tetracarboxylate groups. Magnetic data analysis shows that antiferromagnetic couplings exist between the manganese(III) ions in [Mn3O] subunit of complex 1. [Copyright &y& Elsevier]