ic7b01965_si_001.pdf (2.17 MB)
Influence of Proton Conducting Cations on the Structure and Properties of 2D Anilate-Based Magnets
journal contribution
posted on 2017-11-01, 13:11 authored by Mario Palacios-Corella, Alejandro Fernández-Espejo, Montse Bazaga-García, Enrique R. Losilla, Aurelio Cabeza, Miguel Clemente-León, Eugenio CoronadoThe syntheses, structures, magnetic,
and proton conductivity properties of a family of bimetallic anilate-based
compounds with inserted alkylammonium cations are presented. The structures
of (Me2NH2)[MnIICrIII(Br2An)3]·2H2O (1), (Et2NH2)[MnIICrIII(Br2An)3] (2), (Et3NH)[MnIICrIII(Cl2An)3] (3),
and [(Et)(i-Pr)2NH][MnIICrIII(Br2An)3]·(CHCl3)0.5·(H2O) (4) contain a 2D anionic network formed by
Mn(II) and Cr(III) ions linked through anilate ligands. In 1, 2, and 3, the hexagonal holes of this
network are occupied by Me2NH2+,
Et2NH2+, or Et3NH+ cations. Interestingly, the small increase of size of the
templating cation in 4 ([(Et)(i-Pr)2NH]+ in the place of Me2NH2+,
Et2NH2+ or Et3NH+), gives rise to a different structure with half of the cations placed
within the layers and the other one in the space between the layers.
This leads to bilayers with an interlayer separation similar to those
of 1, 2, and 3 separated by
larger interbilayer distances. Compounds 1, 2, and 3 show a ferrimagnetic ordering with a Tc of 8.0 K (1), 8.9 K (2), and 8.0 K (3). In 4, the presence of
different interlayer distances leads to a metamagnetic behavior when
the sample is measured in contact with the mother liquor. The behavior
changes in the dry sample, which shows a ferrimagnetic ordering as
that of 1, 2, and 3 due to
collapse of the structure as confirmed by powder X-ray diffraction.
Interestingly, the metamagnetic behavior is recovered after reimmersing
the crystals in the mother liquor proving the reversibility of the
process. All solids are Grotthuss-type proton conductors with conductivity
values ranging between 2.3 × 10–6 S·cm–1 for 3 and 2.4 × 10–5 S·cm–1 for 1 measured at 70
°C and 95% relative humidity and activation energies of ∼0.2
eV.