Hydrothermal synthesis, crystal structure, spectroscopic and magnetic properties of Mn4(H2O)3(SeO3)4 and Mn3(H2O)(SeO3)3

Abstract

Two new manganese(II) selenites with the formula Mn₄(H₂O)₃(SeO₃)₄ (1) and Mn₃(H₂O)(SeO₃)₃ (2) have been synthesized by using mild hydrothermal conditions under autogeneous pressure. The crystal structure of both compounds has been solved from single crystal X-ray data. The structures consist of a three-dimensional framework formed by MnO₆ octahedra and (SeO₃)²⁻ selenite anions with trigonal pyramidal geometry. Compound 1 shows the existence of sheets constructed from zig-zag chains linked to MnO₆ octahedra. Compound 2 exhibits zig-zag chains formed by edge-sharing dimeric octahedra which are interconnected by Mn₂O₁₀ octahedra. The IR and Raman spectra show the characteristic bands of the selenite anion. Studies of luminescence at 6.0 K and diffuse reflectance spectroscopy have been carried out for both compounds. The Dq and Racah parameters are Dq = 715, B = 705 and C = 3420 cm⁻¹ for 1 and Dq = 710, B = 700 and C = 3425 cm⁻¹ for 2. The ESR spectra are isotropic with a g-value of 2.00(1), which remains unchanged with variation in temperature. Magnetic measurements indicate the presence of antiferromagnetic interactions in both phases.