Emilie Delahaye

New layered organic-inorganic magnets incorporating azo dyes

New hybrid organic/inorganic magnets have been synthesized by insertion of stilbazolium-carboxylate and/or -sulfonate dyes into cobalt and copper layered hydroxides. Co2(OH)3.57(MR)0.43·1.88 H2O (MR⊂Co (1)) (MRNa: Methyl Red sodium salt: sodium 2-[4-(Dimethylamino)phenylazo]benzoate), Co2(OH)3.27(MO)0.73·2.94 H2O (MO⊂Co (2)) (MONa: Methyl Orange sodium salt: sodium 4-[4-(Dimethylamino)phenylazo]benzenesulfonate), Co2(OH)3.45(OrangeIV)0.55·2.92 H2O (OrangeIV⊂Co (3)) (OrangeIVNa: OrangeIV sodium salt: sodium 4-[4-(Anilino)phenylazo]benzenesulfonate), and Co2(OH)3.46(MY10)0.27·2.34 H2O (MY10⊂Co (4)) (MY10Na2: Mordant Yellow 10 disodium salt: sodium 3-[4-(sodium sulfonate)phenylazo]-6-hydroxybenzoate) have been synthesized by anionic exchange in alkaline media starting from Co2(OH)3(OAc)·H2O. Cu2(OH)3.23(MR)0.77·2.92 H2O (MR⊂Cu (5)), Cu2(OH)3.29(MO)0.71·2.31 H2O (MO⊂Cu (6)), and Cu2(OH)3.39(OrangeIV)0.61·1.80 H2O (OrangeIV⊂Cu (7)) were obtained starting from the pre-intercalated copper hydroxide Cu2(OH)3(DS) (DS−: dodecylsulfate). This is the first time pre-intercalation is used for the insertion of molecules within the interlamellar space of simple layered hydroxides. The hybrid copper layered hydroxides show ferrimagnetic behaviour with ordering at very low temperature (below 1.8 K). The cobalt analogues are ferrimagnets with ordering temperatures ranging from 6.9 K to 18 K.

Hydrothermal Crystallization of Uranyl Coordination Polymers Involving an Imidazolium Dicarboxylate Ligand: Effect of pH on the Nuclearity of Uranyl-Centered Subunits

Four uranyl-bearing coordination polymers (1-4) have been hydrothermally synthesized in the presence of the zwitterionic 1,3-bis(carboxymethyl)imidazolium (= imdc) anion as organic linkers after reaction at 150 °C. At low pH (0.8-3.1), the form 1 ((UO2)2(imdc)2(ox)·3H2O; ox stands for oxalate group) has been identified. Its crystal structure (XRD analysis) consists of the 8-fold-coordinated uranyl centers linked to each other through the imdc ligand together with oxalate species coming from the partial decomposition of the imdc molecule. The resulting structure is based on one-dimensional infinite ribbons intercalated by free water molecules. By adding NaOH solution, a second form 2 is observed for pH 1.9-3.9 but in a mixture with phase 1. The pure phase of 2 is obtained after a hydrothermal treatment at 120 °C. It corresponds to a double-layered network (UO2(imdc)2) composed of 7-fold-coordinated uranyl cations linked via the imdc ligands. In the same pH range, a third phase ((UO2)3O2(H2O)(imdc)·H2O, 3) is formed: it is composed of hexanuclear units of 7-fold- and 8-fold-coordinated uranyl cations, connected via the imdc molecules in a layered assembly. At higher pH, the chain-like solid (UO2)3O(OH)3(imdc)·2H2O (4) is observed and composed of the infinite edge-sharing uranyl-centered pentagonal bipyramidal polyhedra. As a function of pH, uranyl nuclearity increases from discrete 8- or 7-fold uranyl centers (1, 2) to hexanuclear bricks (3) and then infinite chains in 4 (built up from the hexameric fragments found in 3). This observation emphasized the influence of the hydrolysis reaction occurring between uranyl centers. The compounds have been further characterized by thermogravimetric analysis, infrared, and luminescence spectroscopy.

Elaboration of Prussian Blue Analogue/Silica Nanocomposites: Towards Tailor-Made Nano-Scale Electronic Devices

The research of new molecular materials able to replace classical solid materials in electronics has attracted growing attention over the past decade. Among these compounds photoswitchable Prussian blue analogues (PBA) are particularly interesting for the elaboration of new optical memories. However these coordination polymers are generally synthesised as insoluble powders that cannot be integrated into a real device. Hence their successful integration into real applications depends on an additional processing step. Nanostructured oxides elaborated by sol-gel chemistry combined with surfactant micelle templating can be used as nanoreactors to confine PBA precipitation and organize the functional nano-objects in the three dimensions of space. In this work we present the elaboration of different CoFe PBA/silica nanocomposites. Our synthetic procedure fully controls the synthesis of PBA in the porosity of the silica matrix from the insertion of the precursors up to the formation of the photomagnetic compound. We present results on systems from the simplest to the most elaborate: from disordered xerogels to ordered nanostructured films passing through mesoporous monoliths.

New metal phthalocyanines/metal simple hydroxide multilayers: experimental evidence of dipolar field-driven magnetic behavior.

A series of new hybrid multilayers has been synthesized by insertion-grafting of transition metal (Cu(II), Co(II), Ni(II), and Zn(II)) tetrasulfonato phthalocyanines between layers of Cu(II) and Co(II) simple hydroxides. The structural and spectroscopic investigations confirm the formation of new layered hybrid materials in which the phthalocyanines act as pillars between the inorganic layers. The magnetic investigations show that all copper hydroxide-based compounds behave similarly, presenting an overall antiferromagnetic behavior with no ordering down to 1.8 K. On the contrary, the cobalt hydroxide-based compounds present a ferrimagnetic ordering around 6 K, regardless of the nature of the metal phthalocyanine between the inorganic layers. The latter observation points to strictly dipolar interactions between the inorganic layers. The amplitude of the dipolar field has been evaluated from X-band and Q-band EPR spectroscopy investigation (Bdipolar ≈ 30 mT).

Microwave-assisted post-synthesis modification of layered simple hydroxides

A new method to functionalize layered simple hydroxides by post-synthesis modification is described. A layered cobalt hydroxide was modified with a molecule bearing a free amino group. We show here that it is possible to post-functionalize the metal hydroxide layers by performing in situ microwave assisted reactions with the free amino group, constituting a new appealing strategy for functionalization of layered solids. The obtained compounds are characterized by ancillary techniques and their magnetic properties were investigated, which show that the inorganic magnetic layers are not deeply affected by the post-functionalization process.

Efficient Microwave-Assisted Functionalization of the Aurivillius-Phase Bi2SrTa2O9

A new method of acidification and subsequent functionalization of the Aurivillius-phase Bi2SrTa2O9 (BST), using microwave irradiation, was developed. This method enables to obtain hybridized phases from layered BST. Functionalization of BST by various kinds of amines and diamines can be achieved in a few hours only, compared to much longer time (over a week) using conventional heating. Good crystallinity of the compounds is kept. In addition, a microwave-assisted preintercalation strategy was developed, allowing inserting new amines (bearing cyclic or aromatic groups) between the oxide layers previously unseen in this type of compound. This work opens new perspectives for the fast and easy functionalization of layered oxides with more elaborated molecules.

Co2+@Mesoporous Silica Monoliths: Tailor‐Made Nanoreactors for Confined Soft Chemistry

Mesoporous silica monoliths with various ordered nanostructures containing transition metal M(2+) cations in variable amounts were elaborated and studied. A phase diagram depicting the different phases as a function of the M(2+) salt/tetramethyl orthosilicate (TMOS) and surfactant P123/TMOS ratios was established. Thermal treatment resulted in mesoporous monoliths containing isolated, accessible M(2+) species or condensed metal oxides, hydroxides, and salts, depending on the strength of the interactions between the metal species and the ethylene oxide units of P123. The ordered mesoporosity of the monoliths containing accessible M(2+) ions was used as a nanoreactor for the elaboration of various transition metal compounds (Prussian blue analogues, Hofmann compounds, metal-organic frameworks), and this opens the way to the elaboration of a large range of nanoparticles of multifunctional materials.

Hybrid interfaces in layered hydroxides: magnetic and multifunctional superstructures by design

Abstract This article is a critical review on layered hybrid organic-inorganic functional structures. We specially discuss a series of results concerning the design of magnetic and multiproperty systems derived from hybridization of layered transition metal hydroxides. A series of hybrid materials showing original magnetic properties are reviewed, which were prepared by functionalization of layered simple hydroxides (LSH) of the general formula M2(OH)3A (M=Co, Cu, Ni, Zn, … and A=NO3-, OAc-, alkylcarboxylates, peptides, metal complexes…). To make the point on this vast family of hybrid compounds, we present first the work investigating the mechanism of interaction and the structural factors influencing the magnetic properties of hybrid materials based on LSH. Then, we detail how even more complex anions can be immobilized and grafted into the interlamellar space giving rise to new functionalities. These systems are very good models for understanding the correlations between the structure of hybrid systems and the physical properties brought by the inorganic host and by the molecular moieties grafted onto the inorganic metal network. The interface between the organic and inorganic components, i.e. chemical bonding, charge density, or local pressure, is essential for the control of the properties of multifunctional hybrid systems. Some conclusions are drawn on the future of this approach, useful for developing new two-dimensional functional systems.