Structural, Magnetic, and Ion-Exchange Properties of RbMnHP(3)O(10)

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.