(3-Fluoro-4-methoxyanilinium)+([18]Crown-6) Supramolecular Cation Salt of Ferromagnetic [MnIICrIII(oxalate)3]−

Abstract

A single crystal of (3-fluoro-4-methoxyanilinium)+([18]crown-6)[MnIICrIII(oxalate)3]−(CH3OH)2 had the space group Cc owing to the arrangement of the 3-fluoro-4-methoxyanilinium+ cation with C1 symmetry and, therefore, was pyroelectric. A ferromagnetic transition at 5.5 K was observed, which originated from the two-dimensional honeycomb structure of the [MnIICrIII(oxalate)3]− anion.

Stable Ferromagnetic Crystal of Two‐Dimensional Manganese‐Chromium Oxalate with Supramolecular Cation

“…Alternate stackings of 2D layer structures formed by the anionic and cationic components were found along the b axis [Figure (a)]. In the anionic layer, the {[Mn II Cr III (oxalate) 3 ] – } anions constructed an infinite 2D honeycomb structure within the ac plane, which is commonly observed in {[Mn II Cr III (oxalate) 3 ] – } crystals , . The distances between mean planes of the anionic layers was about 12 Å.…”

“…In the anionic layer, the {[Mn II Cr III (oxalate) 3 ] -} anions constructed an infinite 2D honeycomb structure within the ac plane, which is commonly observed in {[Mn II Cr III (oxalate) 3 ] -} crystals. [12,13] The distances between mean planes of the anionic layers was about 12 Å. Positions of manganese and chromium ions in the 2D honeycomb layer can be determined by using bond lengths between each metal ion and oxygen atoms of the oxalate ligands, with ranges of 1.9-2.0 and 2.1-2.2 Å for Cr-O and Mn-O bonds, respectively.…”

“…On lowering the temperature below 10 K, the m T value increased rapidly, reaching 300 emu K mol -1 at 5.0 K. The m T vs. T plot indicated Curie-Weiss behavior with ferromagnetic coupling with a Weiss temperature (θ) of +6.7 K. The behavior is similar to those reported for other crystals with 2D honeycomb layers. [9,12,13] For the AC magnetic susceptibility [ Figure 5(b)], signals of the real part showed peaks at 5.5 K without frequency dependence, and signals of the imaginary part started to rise at 5.5 K, indicating that the ferromagnetic ordering occurred at 5.5 K. Figure 5(c) shows the magnetization (M)-magnetic field (H) curve at 2 K. The magnetization saturated at ±1 T reaching ±8.3 μ B , corresponding to a ferromagnetic spin arrangement for high-spin S = 5/2 and S = 3/2 on the Mn II and Cr III sites, respectively (8 μ B ). [12] Small hysteresis in the M-H curve suggested soft ferromagnetic behavior, as observed in the other 2D honeycomb {[Mn II Cr III (oxalate) 3 ] -} crystals.…”

“…[12] Small hysteresis in the M-H curve suggested soft ferromagnetic behavior, as observed in the other 2D honeycomb {[Mn II Cr III (oxalate) 3 ] -} crystals. [9,12,13]…”

“…In the course of study, we reported on several crystals of {[Mn II Cr III (oxalate) 3 ] – } with supramolecular cations. Although the {[Mn II Cr III (oxalate) 3 ] – } exhibited various dimensionalities in the crystals, such as 3D cage structures and typical 2D layers, these crystals tend to incorporate crystal solvent in the frameworks. The {[Mn II Cr III (oxalate) 3 ] – } networks have large pores – the size of a typical 2D honeycomb pore is 10–11 Å in diameter , .…”