Crystal Structure and Preferential Site Occupancy in Cs6Mn(H2O)2(VO3)8 and Cs5KMn(H2O)2(VO3)8

Two new structurally related cesium manganese vanadates have been synthesized by a high-temperature (580 degrees C) hydrothermal synthetic method utilizing halide brine mineralizers. Both structures Cs6Mn(H2O)(2)(VO3)(8) (I) and Cs5KMn(H2O)(2)(VO3)(8) (II) are isostructural crystallizing in the tetragonal space group P4/mnc. The first structure, Cs6Mn(H2O)(2)(VO3)(8) (I) has unit cell dimensions of a=13.6830(4)angstrom, c=8.6476(3)angstrom and the second structure, Cs5KMn(H2O)(2)(VO3)(8) (II), has unit cell dimensions of a=13.5015(4)angstrom, c=8.5372(3)angstrom. The structures are built from a manganese vanadate chain, which consists of [Mn(H2O)(2)O-4] units that are coordinated to one another by a unique sinusoidal vanadate chain, (VO3)(n). Both structures have well-ordered alkali metal atoms, with the potassium atoms of II exhibiting preferential site occupancy. Both compounds were characterized by single crystal X-ray diffraction and infrared spectroscopy, to identify the characteristic O-H and V-O modes.