Influence of the cation size on the formation of alluaudite-type manganese arsenates: synthesis and characterization of Tl 2Mn 3(As 2O 7) 2·2H 2O, CsMn 3(AsO 4)(HAsO 4) 2·3H 2O, and XMn 3(AsO 4)(HAsO 4) 2 (X=Na, K)

Abstract

Two isotypic manganese-arsenates, XMn 3(AsO 4)(HAsO 4) 2 (X=K( 1),Na( 2)), with a structure related to the mineral alluaudite, have been synthesized and characterized by single crystal X-ray diffraction. Crystal data: ( 1) KMn 3(AsO 4)(HAsO 4) 2, monoclinic, C2/c, a=12.706(3), b=12.731(3), c=6.937(2), β=113.175(5), Z=4; ( 2) NaMn 3(AsO 4)(HAsO 4) 2, monoclinic, C2/c, a=12.299(3), b=12.735(3), c=6.893(2), β=113.587(4), Z=4. The use of larger cations under similar synthesis conditions led to the formation of two layered compounds, CsMn 3(AsO 4)(HAsO 4) 2·3H 2O ( 3) and Tl 2Mn 3(As 2O 7) 2·2H 2O ( 4), which were also obtained in the form of single crystals and characterized by single crystal X-ray diffraction. Crystal data: ( 3) CsMn 3(AsO 4)(HAsO 4) 2·3H 2O, monoclinic, P2 1/c, a=16.3389(11), b=6.6912(4), c=13.2538(9), β=98.666(1), Z=4; ( 4) Tl 2Mn 3(As 2O 7) 2·2H 2O, monoclinic, P2 1/c, a=9.576(7), b=8.478(6), c=9.735(7), β=99.117(13), Z=2. TGA/MS, IR and magnetic susceptibility measurements on powder samples of 1, 2, and 3 were performed.