A New Layered Inorganic−Organic Hybrid Manganese(II) Phosphite: (C₂H₁₀N₂)[Mn₃(HPO₃)₄]. Hydrothermal Synthesis, Crystal Structure, and Spectroscopic and Magnetic Properties

Abstract

A new manganese(II) phosphite templated by ethylenediamine has been prepared by hydrothermal synthesis and characterized by X-ray diffraction data and spectroscopic techniques. A study of the evolution of the synthetic process suggests the presence of a manganese(II) phosphite as intermediate in the first steps of the reaction. The (C2H10N2)[Mn3(HPO3)4] compound crystallizes in the triclinic space group P-1 with a = 5.459(1) Å, b = 5.460(2) Å, c = 14.194(5) Å, α = 80.65(2)°, β = 85.41(1)°, γ = 60.04(2)°, V = 361.7(2) Å3, and Z = 1. The compound exhibits a layered structure along the c axis with the ethylenediammonium cations located between the sheets. Within the layers the face-sharing MnO6 octahedra give rise to trimeric entities which are interconnected by HPO3 tetrahedra. Studies of luminescence and diffuse reflectance spectroscopies have been carried out. The values of the Dq = 875 cm-1 and Racah parameters, B = 660 and C = 3160 cm-1, have been calculated. The ESR spectra at different temperatures show isotropic signals with a g value of 2.01, which remains unchanged with variation in temperature. The thermal evolution of both the intensity and the line width of the ESR signals shows an increase from room temperature to 4.2 K. From the magnetic measurements the presence of antiferromagnetic interactions in the compound can be observed. The high-temperature magnetic data have been fitted to a model for linear isolated trimers of Mn(II) with a J exchange parameter of −17 K. At temperatures lower than ca. 80 K a long magnetic order, propagated via phosphite anions along the sheets, is established.