STRUCTURE AND SPECTROSCOPY OF SODALITE CONTAINING MNO4- IONS

Permanganate ions were encapsulated in sodalite cages during the hydro thermal synthesis of basic sodalite in the presence of excess sodium p ermanganate. Both spectroscopic and structural studies of the solid so lutions of basic sodium-permanganate-aluminosilicate sodalite focus on a particular stoichiometry: Na-4-[AlSiO4] (3)(MnO4)(r)(OH)(1-x) with x = 0.73. The most important spectroscopic findings include 8-cm(-1) s plitting of the v(3) (908 cm(-1)) asymmetric stretch and 300-cm(-1) sp litting of the orbitally degenerate T-1(2) state of the MnO4- ion. The se results provide evidence for departure of MnO4- in sodalite cages f rom T-d symmetry, in contradiction with the X-ray Rietveld analysis, w hich suggests a cubic lattice with a = 9.0992(7) Angstrom and preserve d P43n crystal symmetry. The apparent discrepancy between structural a nd spectroscopic data is explained, and the reasons for the lowered sy mmetry are discussed.