Synthesis, structure, and magnetic property of a new open-framework manganese borophosphate, [NH4](4)[Mn9B2(OH)(2)(HPO4)(4)(PO4)(6)]

A new three-dimensional (3-D) manganese(II) borophosphate, [NH4](4)[Mn9B2(OH)(2)(HPO4)(4)(PO4)(6)] (denoted MnBPO-CJ26), has been synthesized by a hydrothermal method. The structure has been determined by single-crystal X-ray diffraction. It crystallizes in the monoclinic space group C2/c (No. 15) with a = 32.603(7) angstrom, b = 10.617(2) angstrom, c = 10.718(2) angstrom, and beta = 108.26(3)degrees. Its structure features anionic manganese-phosphate layers [Mn-9(OH)(2)(HPO4)(4)(PO4)(6)](10-), which are made up from MnO5, MnO6, PO4, and HPO4 polyhedral units. These anionic layers, parallel to the bc plane, are further connected by BO4 tetrahedra through vertex oxygen atoms forming a novel open framework with 2-D eight-membered ring (8-MR) channels along the [010] and [001] directions. Charge neutrality is achieved by protonated NH3 molecules. The structure has unique B/P and Mn/P ratios (B/P = 1/5, Mn/P = 9/10). Magnetic measurements indicate that Curie-Weiss behavior above 100 K with C = 4.404(3) cm(3) mol(-1) K and theta = -51.2(5) K. The value of C is consistent with an S = (5)/(2) ion with g similar to 2.0 (4.38 cm(3) mol(-1) K). However, the magnetic data reveal a spontaneous magnetization at 8.0 K, indicating a canting of Mn2+ moments in the antiferromagnetic ground state.Chemistry, PhysicalMaterials Science, MultidisciplinarySCI(E)EI43ARTICLE2476-4811