Unique charge ordering of manganese in a new mixed valent phosphate

✍ Scribed by L. Adam; A. Guesdon; B. Raveau

• Publisher: Elsevier Science
• Year: 2009
• Tongue: English
• Weight: 309 KB
• Volume: 182
• Category: Article
• ISSN: 0022-4596
• DOI: 10.1016/j.jssc.2009.06.017

✦ Synopsis

A new mixed-valent manganese phosphate, K 3 Mn II 3 Mn III ðPO 4 ÞðH 0:5 PO 4 Þ 2 ðHPO 4 Þ 2 , has been synthesized using hydrothermal method. Its monoclinic C2/c structure (a ¼ 12.5506( 16) Å, b ¼ 10.4816(18) Å, c ¼ 13.6723(10) Å, b ¼ 103.758(11)1) forms a 3D framework of MnO 6 octahedra, MnO 5 trigonal bipyramids, PO 4 and PO 3 OH tetrahedra. The main structural feature of this phosphate deals with its [Mn 4 O 16 ] N chains running along c, which are interconnected through PO 4 and PO 3 OH tetrahedra, forming intersecting tunnels running along [110], ½110 and [001]. The geometry of the [Mn 4 O 16 ] N chains and the charge ordering of manganese in the latter are unique: they consist of trimeric units of divalent manganese ''Mn II 3 O 12 '' alternating with single trivalent Mn III O 6 octahedra along c. In each ''Mn II 3 O 12 '' unit one central Mn II O 6 octahedron shares two opposite edges with two Mn II O 5 trigonal bipyramids. Along c, 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.