Structural and spectroscopic study of organic-inorganic transition metal based layered magnets

Abstract

IntroductionRecently, a novel trend of investigation has been the combination of both molecular and solid state chemistry to build hybrid organic-inorganic materials [1]. Clearly, the research on hybrid compounds is very appealing for the design of novel 3d networks in which the physical properties of both assemblies, that are normally found in distinct materials, are in close conjunction [2][3][4][5].Smectite clay minerals (montmorillonite for instance), in which silicate layers are negatively charged by substituting divalent metal ions for trivalent ones, constitute versatile host layer structures for organic or inorganic species. A large number of such cation exchangeable layer compounds are known in which the intercalated species favor pillared structures.Anion exchangeable layered compounds are less common, probably because the anions are usually strongly bound to the metal ions, and form the framework of the crystal. Exchange of interlamellar anions by organic species (dicarboxylic acid anions) was first reported by Miyata and Kumura [6]. Then, the interlayer arrangement of anionic surfactants has been extensively studied in layered double-consisting of positively charged hydroxide layers, separated by A -anions counter-balancing the positive charge of the hydroxy layers [3,4,7,8]. In such compounds, the counterion A -is located in between the hydroxy layers, and no real chemical bond exists usually between the guest and host sub-networks. The cohesion is basically due to electrostatic interactions, and when available to weak hydrogen bond couplings.On the other hand, new hybrid magnetic materials have been prepared by anion exchange reaction, in which the exchangeable anion A -is coordinated to the divalent metal ion. The layered compounds M 2 (OH) 3 A (M = Co, Cu, and A = NO 3 -or OAc -) are shown to be well adapted for substitution reactions [9][10][11][12]. The exchange for large organic species (i.e. aliphatic chain anions) coordinating the metal ion enables to tune the basal spacing, and accordingly to modify drastically the magnetic properties [11,12]. Thus, nalkyl chain molecules involving a single anionic function (carboxylate or sulfate anion), have been used to separate basic layers (Fig. 1a).In that case, the organic spacers exhibit a saturated carbon chain, whose length is mediated by the number of carbon atoms, up to 40 Å [10]. The magnetic interaction within layers is highly dependent on the nature of the anionic function and the chain stacking, so that ferro-, ferri-or antiferromagnetic behavior may be stabilized. Clearly, the n-alkyl chains do not participate directly to interlayer interactionthey may be viewed as "neutral'' pillars -but they modulate the distance between magnetic sheets, and as a result influence through-space magnetic interactions. We have shown that, due to dipolar coupling [13], ferromagnetic 3d order is stabilized when basal spacing becomes large enough (> 10 Å). The interaction mechanism between ferromagnetic layers is then mainly driven by the divergence of the inpl...

Anion Exchange Kinetics of Nanodimensional Layered Metal Hydroxides: Use of Isoconversional Analysis

“…ZC-Ac has a broad peak centered around 3400 cm −1 which is due to O−H stretch of hydrogen bonded water and/or layer hydroxyl groups. Upon exchanging acetate with Cn, the broad hydroxyl band in ZC-Ac was replaced by a single sharp peak at 3577 cm −1 in ZC-Cn; this is consistent with losing water of intercalation as the acetate ion was replaced by Cn resulting resulting in the layer hydroxyl groups being free, 38 consistent with elemental analysis data, Table S1, and TGA data, Figure S2, provided in Supporting Information.…”

“…Broad absorption bands in the OH stretching region have been shown to disappear with hydrous -anhydrous transformation, with the appearance of sharp absorption bands around 3600 cm −1 . 38 ZC-Ac prepared in this work is layered and possesses high range ordering in the c direction as shown in the lower panel of Figure 3A; the PXRD profile show intense 00l (l = 1 to 3) Bragg reflections which are equally spaced. The interlayer distance of 9.43 ± 0.03 Å obtained for ZC-Ac is comparable to literature values (9.3 Å and 9.46 Å) reported for material prepared using the same method.…”

On verdigris, part II: synthesis of the 2-1-5 phase, Cu3(CH3COO)4(OH)2·5H2O, by long-term crystallisation from aqueous solution at room temperature

“…12,13,[21][22][23] These investigations however were focused mainly on the 1-3-2 phase. The crystal structure of the 1-3-2 phase was solved both from powder 7 and single crystal 8 X-ray diffraction.…”

Modification of the Interlayer Surface of Layered Copper(II) Hydroxide Acetate with Benzoate Groups: Submicrometer Fiber Generation

“…Low-intensity bands observed at 3609, 3576, 3520, 3449, 3403, and 3263 cm −1 attributed to water and matrix hydroxide groups were substituted by very well defined absorption bands at 3613, 3601, and 3586 cm −1 . In the grafted phase the demonstrate that the organic molecule was added to the host due to the characteristic C-H vibrations (20)(21)(22)(23). The absorption bands in the 3000-3100 cm −1 region grow in intensity in correlation with benzoic acid proportion.…”