Structural, Magnetic, and Ion-Exchange Properties of RbMnHP₃O₁₀

Abstract

The crystal structure, magnetic properties, and ion-exchange behavior of RbMnHP(3)O(10) have been determined. The crystal structure (a = 12.1866(3) Å, b = 8.3586(2) Å, c = 9.0763(3) Å, beta = 109.067(1) degrees, space group C2/c), determined from X-ray powder diffraction, is of NH(4)FeHP(3)O(10) type, consisting of hydrogen triphosphate anions linking Jahn-Teller distorted Mn(III)O(6) octahedra around Rb(+) cations. Magnetic susceptibility measurements and low-temperature neutron powder diffraction show that RbMnHP(3)O(10) behaves as a Curie-Weiss paramagnet at high temperatures and orders antiferromagnetically below a Néel temperature of 10 K. The magnetic structure is commensurate with the nuclear cell, and the collinear antiferromagnetic structure has magnetic symmetry group P(C)()2/c' with spins of 3.82(6) &mgr;(B) lying in the ac plane. Exchange of H(+) for Li(+) has not proved possible without a breakdown of the RbMnHP(3)O(10) framework due to strong symmetric hydrogen bonding between triphosphate anions.

Crystal structure of o-aminopyridinium dihydrogenmonophosphate, (NH2C5H4NH)[H2PO4]

“…This has permitted to every unit to connect four of its neighbors through strong symmetrical hydrogen bonds of the O-HO type (Ol -Ol' = 2.470(2) A and03-03'=2.466(2) A), thus giving three-dimensional anionic network. Similar strong symmetrical hydrogen bonds are found in crystal structures of other phosphates, such as CSM11HP3O10 [1], RbMnHPsOio [2] and [0C4H8N(CH3)CH2C00H3P04] [3], The pyridine ring of the organic cation is planar, with a mean plane deviation of 0.0045(1) A. The C5-N2 bond length of 1.323(2) A is approximately equal to C=N double bond length, indicating that N2 atom of the amino group must be sp 2 hybridized.…”

Manganese(iii) fluorophosphate frameworks

“…Only relatively few examples of Mn(III) containing structures are known; reported Mn(III) phosphate compositions and structures include the MMn(III)HP 3 O 10 (M = Rb, Cs) series and manganese violet pigments. 4,[13][14][15] Mn(III) compounds have recently been the focus of extensive research due the collosal magnetoresistive effects exhibited by phases such as Pr 0.7 Ca 0.3−x Sr x MnO 3−δ . 16 The incorporation of fluoride into the synthesis schemes of framework materials can have an influence in a number of ways.…”

Jahn−Teller Distorted Frameworks and Magnetic Order in the Rb−Mn−P−O System

“…This leads to significant structural diversity in transition-metal diphosphate systems, as evident in A I M III P 2 O 7 ( A I = alkali metal, M III = V, Fe, Mo), , where the framework consists of corner-sharing M O 6 octahedra and P 2 O 7 units. Similarly, although less studied, triphosphate anions (P 3 O 10 5− ) are known to form frameworks with transition metals, − providing further examples of metal−phosphate framework topologies.…”

“…This system was first investigated in 1988 by Guzeeva and Tananaev, who identified a number of distinct phases, including RbMnP 2 O 7 and two polymorphs of RbMnHP 3 O 10 (previously labeled I and II, hereafter referred to as α and β, respectively, for consistency with the standard polymorph labeling), and reported their syntheses and X-ray powder diffraction patterns but provided no further structural details. Previous studies by Wright and Attfield have solved the nuclear and magnetic structure of α-RbMnHP 3 O 10 . Here we report for the first time the nuclear and magnetic structures of two further phases from the Rb−Mn−P−O system, β-RbMnHP 3 O 10 and RbMnP 2 O 7 , enabling a detailed comparison with related frameworks containing Mn 3+ and allowing the further investigation of exchange interactions between orbitally ordered Mn 3+ ions mediated through phosphate linkages.…”