Sawtooth chains self-assembled from clusters of MnO6 octahedra within the silicate framework of K3Mn4Si10O24.33(H2O,OH)3/V,B

Abstract

Single crystals of a novel phase, potassium manganese silicate hydrate, K₃Mn₄Si₁₀O_24.33(H₂O,OH)₃, doped with B and V, were obtained under hydrothermal conditions and studied using scanning electron microscopy, microprobe analysis and low temperature synchrotron X-ray diffraction. The title structure represents an original silicate framework assembled from layers with various n-membered SiO₄ rings that restrict channels open in the [001] direction. The corrugated chains of face-sharing MnO₆ octahedra are incorporated into the space between “pendant” vertices of the tetrahedra framing 12-membered windows. This is the first example of combining two topologically different trimeric clusters of octahedra sharing faces into a single construction. The framework channels with 5- and 6-membered windows incorporate K atoms, and H₂O molecules are located in the channels with 7-membered openings. We assume that the stability of this crystal structure is due to the partial substitution of Mn for V and Si for B. The magnetic subsystem in the title compound represents a rare case of the quasi-one-dimensional arrangement of MnO₆ octahedra forming sawtooth-like chains. Measurements of magnetization and heat capacity of K₃Mn₄Si₁₀O_24.33(H₂O,OH)₃/V,B indicate the absence of long-range order up to 2 K. Structural features of the K₃Mn₄Si₁₀O_24.33(H₂O,OH)₃/V,B allow supposing it as potential multifunctional material, electrochemically active and having properties of low-dimensional magnet.