Unique charge ordering of manganese in a new mixed valent phosphate K3Mn3IIMnIII(PO4)(H0.5PO4)2(HPO4)2

A new mixed-valent manganese phosphate, (K3Mn3MnIII)-Mn-II(PO4)(H0.5PO4)(2)(HPO4)(2), has been synthesized using hydrothermal method. Its monoclinic C2/c structure (a = 12.5506(16) angstrom, b = 10.4816(18) angstrom, c = 13.6723(10) angstrom, beta = 103.758(11)degrees) forms a 3D framework of MnO6 octahedra, MnO5 trigonal bipyramids, PO4 and PO3OH tetrahedra. The main structural feature of this phosphate deals with its [Mn4O16](infinity) chains running along (c) over right arrow, which are interconnected through PO4 and PO3OH tetrahedra, forming intersecting tunnels running along [110], [1 (1) over bar0] and [001]. The geometry of the [Mn4O16](infinity) chains and the charge ordering of manganese in the latter are unique: they consist of trimeric units of divalent manganese "(Mn3O12)-O-II" alternating with single trivalent (MnO6)-O-III octahedra along (c) over right arrow. In each "(Mn3O12)-O-II" unit one central (MnO6)-O-II octahedron shares two opposite edges with two (MnO5)-O-II trigonal bipyramids. Along (c) over right arrow, one Mn(II) octahedron alternates with one Mn III) octahedron by sharing one corner. The relationships between the structure of this unique charge ordered phosphate and other manganese phosphates are discussed. (C) 2009 Elsevier Inc. All rights reserved.