RESUMO
The magnetodielectric effect is closely related to multiferroic or magnetoelectric coupling; thus, it can be used to predict magnetoelectric coupling, especially in compounds with special magnetic properties. The magnetodielectric response can often be used to predict many interesting and meaningful physical coupling mechanisms. Therefore, fabricating magnetodielectric materials is an effective step toward the development of magnetoelectric materials. Herein, we synthesize the mixed-valence layered ferrimagnetic molecular compound (C6N2H14)FeIII2FeIIF8(HCOO)2 (1) and demonstrate that it exhibits both slow magnetic relaxation behavior and long-range magnetic order. This long-range order occurs because of the coexistence and competition between two typical magnetic interactions, namely, an FeIII-F-FeII superexchange and a long-distance superexchange FeII-O-C-O-FeIII-F-FeIII path in the interlayer and interchain spin frustration. Notably, this compound also demonstrates two abnormal dielectric relaxation processes: the first process is dominated by dynamic guest cations, while the other process is related to the increasing magnetic correlation. Over a wide temperature range below 170 K, the magnetodielectric effect reveals that the magnetic correlation maybe promotes electron dynamics and leads to magnetodielectric coupling. These findings pave a novel path for designing magnetodielectric molecular materials.
RESUMO
Two isostructural 3D Hofmann-type frameworks, [FeII(dbdpe)MII(CN)4]·4H2O (M = Pt for 1 and Pd for 2), were synthesized based on a bis-monodentate ligand dbdpe (1,2-dibromo-1,2-di(pyridin-4-yl)ethane). Both compounds underwent similar one-step incomplete spin crossover (SCO) processes in the presence of lattice water molecules, i.e., T1/2↓ = 185 K for 1 and 187 K for 2 without any hysteresis loop, while their dehydrated products exhibited paramagnetic behaviours. The application of pressure on 1 broadened the hysteresis loop to 13-25 K and shifted the transition temperature from 185 to 298 K, whereas the SCO completeness was not well improved. Variable temperature X-ray crystallographic studies clearly confirmed the incomplete SCO behaviors, and the intermolecular hydrogen bonds might promote the cooperativity in the SCO processes.
RESUMO
Polar organic-inorganic hybrid materials have been applied in ferroelectricity, as well as in devices based on nonlinear optical and piezoelectricity properties. Here, we used a rectangular pyramid structure of [VOCl4]2- to construct a polar compound (C5NH13Cl)2VOCl4 (1). Compound 1 crystallized in the monoclinic P21 space group. Coexistence of nonlinear optical switching behavior (space-group change from P21 to P21/n) and two-staged thermosensitive dielectric switching properties could be achieved under the stimulus of temperature. Our findings provide an effective approach for construction of polar materials.