A New Manganese(II) Phosphate Templated by Ethylenediamine: (C₂H₁₀N₂)[Mn₂(HPO₄)₃(H₂O)]. Hydrothermal Synthesis, Crystal Structure, and Spectroscopic and Magnetic Properties

Abstract

A new manganese(II) phosphate templated by ethylenediamine, (C2H10N2)[Mn2(HPO4)3(H2O)], has been prepared by hydrothermal synthesis and characterized by single-crystal diffraction data and spectroscopic and magnetic techniques. The compound crystallizes in the monoclinic space group P21/n with a = 21.961(7), b = 9.345(1), c = 6.639(2) Å; β = 91.06(2)°; V = 1362.3(6) Å3; and Z = 4. The structure consists of anionic sheets of formula [Mn2(HPO4)3]2-, being the charge compensated by ethylendiammonium cations. The sheets are constructed by edge-sharing MnO6 octahedra, MnO5 trigonal bipyramids, and hydrogen phosphate tetrahedra. Within a layer, the edge-sharing octahedra and the trigonal bipyramids are linked in an alternating way, forming zigzag chains along the [001] direction. The ethylenediammonium cations and the water molecules are located in the interlayer space. The compound has been characterized by IR spectroscopy. A study of the compound by luminescence and diffuse reflectance spectroscopies is carried out. The Dq and Racah parameters have been calculated for Mn(II) ions in octahedral sites. The ESR spectra at different temperatures of the compound show isotropic signals, with a g value that remains unchanged with variation in temperature. The intensity and the line width of the ESR signals increase continuously from room temperature to 4.2 K. Magnetic measurements from room temperature to 1.8 K indicate the presence of antiferromagnetic interactions. A value of J/k = −0.75 K for the exchange parameter has been calculated by fitting the experimental magnetic data to a triangular lattice antiferromagnet of S = 5/2 spins.