Layered manganese and copper phosphonates with metamagnetism observed in Mn(2-pmp)(H2O)2·H2O (2-pmpH2 = 2-pyridylmethylphosphonic acid)

Hydrothermal reactions of 2-pyridylmethylphosphonic acid (2-pmpH2) and corresponding metal salts lead to two new layered compounds Mn(2-pmp)(H2O)2·H2O (1) and Cu(2-pmp)(H2O) (2). The {MnO5N} octahedra in 1 or {CuNO4} square pyramids in 2 are each corner-shared with the {PO3C} tetrahedra, forming inorganic layers containing alternative 8- and 16-membered rings. The organic groups graft on the two sides of the inorganic layers. The layers are packed in different fashions, resulting in interlayer distances of 10.0876 Å in 1 and 8.548 Å in 2. Magnetic measurements reveal that dominant antiferromagnetic interactions are found between metal ions in both cases. At low temperature, compound 1 shows metamagnetism with a critical field of 35 kOe at 1.8 K, while compound 2 displays an antiferromagnetism.