Hydroxy Double Salts Research Articles

In Situ Time-Resolved Attenuated Total Reflectance Infrared Spectroscopy for Probing Metal-Organic Framework Thin Film Growth.

In situ chemical measurements of solution/surface reactions during metal-organic framework (MOF) thin film growth can provide valuable information about the mechanistic and kinetic aspects of key reaction steps, and allow control over crystal quality and material properties. Here, we report a new approach to study the growth of MOF thin films in a flow cell using attenuated total reflectance Fourier transform infrared spectroscopy (ATR-FTIR). Real-time spectra recorded during continuous flow synthesis were used to investigate the mechanism and kinetics that govern the formation of (Zn, Cu) hydroxy double salts (HDSs) from ZnO thin films and the subsequent conversion of HDS to HKUST-1. We found that both reactions follow pseudo-first order kinetics. Real-time measurements also revealed that the limited mass transport of reactants may lead to partial conversion of ZnO to HDS and therefore leaves an interfacial ZnO layer beneath the HDS film providing strong adhesion of the HKUST-1 coating to the substrate. This in situ flow-cell ATR-FTIR method is generalizable for studying the dynamic processes of MOF thin film growth, and could be used for other solid/liquid reaction systems involving thin films.

Hydroxy double salts loaded with bioactive ions: Synthesis, intercalation mechanisms, and functional performance

The intercalation of the anions of diclofenac (Dic), naproxen (Nap), and valproic acid (Val) into three hydroxy double salts (HDSs) has been explored in this work. Experiments were performed with [Co1.2Zn3.8(OH)8](NO3)2·2H2O (CoZn-NO3), [Ni2Zn3(OH)8](NO3)2·2H2O (NiZn-NO3) and [Zn5(OH)8](NO3)2·2H2O (Zn-NO3). It proved possible to intercalate diclofenac and naproxen into all three HDSs. In contrast, Val could be intercalated into CoZn-NO3 but when it was reacted with Zn-NO3 the HDS structure was destroyed, and the product comprised ZnO. Successful intercalation was verified by X-ray diffraction, IR spectroscopy, and elemental microanalysis. Molecular dynamics simulations showed the Dic and Nap ions to arrange themselves in an “X” shape in the interlayer space, forming a bilayer. Val was found to adopt a position with its aliphatic groups parallel to the HDS layer, again in a bilayer. In situ time resolved X-ray diffraction experiments revealed that intercalation of Dic and Nap into CoZn-NO3 and Zn-NO3 is mechanistically complex, with a number of intermediate phases observed. In contrast, the intercalation of all three guests into NiZn-NO3 and of Val into CoZn-NO3 are simple one step reactions proceeding directly from the starting material to the product. The HDS-drug composites were found to have sustained release profiles.

Hydroxy double salts intercalated with Mn(II) complexes as potential contrast agents

A series of Mn(II) aminophosphonate complexes were successfully synthesized and intercalated into the hydroxy double salt [Zn5(OH)8]Cl2·yH2O. Complex incorporation led to an increase in the interlayer spacing from 7.8 to 10–12 Å. Infrared spectroscopy showed the presence of the characteristic vibration peaks of the Mn(II) complexes in the intercalates' spectra, indicating successful incorporation. The complex-loaded composites had somewhat lower proton relaxivities than the pure complexes. Nevertheless, these intercalates may have use as MRI contrast agents for patients with poor kidney function, where traditional Gd(III)-based contrast agents cause severe renal failure.

New biocompatible hydroxy double salts and their drug delivery properties.

Two biocompatible hydroxy double salts (HDSs) were synthesised for the first time and loaded with active pharmaceutical ingredients. Drug release was studied from these intercalates, and sustained release observed. The HDS-drug composites were further formulated into tablets which were found to comply with pharmacopeia requirements for delayed and extended release dosage forms.

Gd(III) complexes intercalated into hydroxy double salts as potential MRI contrast agents.

The ion exchange intercalation of two Gd-based magnetic resonance imaging contrast agents into hydroxy double salts (HDSs) is reported. The presence of Gd(3+) diethylenetriaminepentaacetate and Gd(3+) diethylenetriaminepenta(methylenephosphonate) complexes in the HDS lattice after intercalation was confirmed by microwave plasma-atomic emission spectroscopy. The structural aspects of the HDS-Gd composites were studied by X-ray diffraction, with the intercalates having an interlayer spacing of 14.5-18.6 Å. Infrared spectroscopy confirmed the presence of characteristic vibration peaks associated with the Gd(3+) complexes in the intercalation compounds. The proton relaxivities of the Gd(3+) complex-loaded composites were 2 to 5-fold higher in longitudinal relaxivity, and up to 10-fold higher in transverse relaxivity, compared to solutions of the pure complexes. These data demonstrate that the new composites reported here are potentially potent MRI contrast agents.

Controlled Release Kinetics in Hydroxy Double Salts: Effect of Host Anion Structure

Nanodimensional layered metal hydroxides such as layered double hydroxides (LDHs) and hydroxy double salts (HDSs) can undergo anion exchange reactions releasing intercalated anions. Because of this, these metal hydroxides have found applications in controlled release delivery of bioactive species such as drugs and pesticides. In this work, isomers of hydroxycinnamate were used as model compounds to systematically explore the effects of anion structure on the rate and extent of anion release in HDSs. Following intercalation and subsequent release of the isomers, it has been demonstrated that the nature and position of substituent groups on intercalated anions have profound effects on the rate and extent of release. The extent of release was correlated with the magnitude of dipole moments while the rate of reaction showed strong dependence on the extent of hydrogen bonding within the layers. The orthoisomer showed a more sustained and complete release as compared to the other isomers.

ChemInform Abstract: The Bonding Nature and Low‐Dimensional Magnetic Properties of Layered Mixed Cu(II)—Ni(II) Hydroxy Double Salts.

AbstractThe compounds (Cu0.75Ni0.25)2 (OH)3NO3 (I) and Cu2(OH)3NO3 (II) are prepared by slow hydrolysis of CuO with aqueous solutions of Ni(NO3)2 and Cu(NO3)2, resp.

The Bonding Nature and Low-Dimensional Magnetic Properties of Layered Mixed Cu(II)-Ni(II) Hydroxy Double Salts

Layered mixed metal hydroxy double salts (HDS) with the formulas (Cu0.75Ni0.25)2(OH)3NO3 ((Cu, Ni)-HDS) and Cu2(OH)3NO3 ((Cu, Cu)-HDS) were prepared via slow hydrolysis reactions of CuO with Ni(NO3)2 and Cu(NO3)2, respectively. The crystal structures, morphologies, bonding natures, and magnetic properties of (Cu, Ni)-HDS and (Cu, Cu)-HDS were characterized with X-ray diffraction (XRD), scanning electron microscopy (SEM), Fourier transformation infrared spectroscopy (FT-IR), thermogravimetric analysis (TGA), and a superconducting quantum interference device (SQUID). Even though (Cu, Ni)-HDS has a similar layered structure to that of (Cu, Cu)-HDS, the bonding nature of (Cu, Ni)-HDS is slightly different from that of (Cu, Cu)-HDS. Therefore, the magnetic properties of (Cu, Ni)-HDS are significantly different from those of (Cu, Cu)-HDS. The origin of the abnormal magnetic properties of (Cu, Ni)-HDS can be explained in terms of the bonding natures of the interlayer and intralayer structures.

Mechanochemical synthesis of layered hydroxy salts

A simple one minute synthesis method was adapted for the preparation of layered hydroxy salts of copper, zinc, nickel and cadmium by grinding the metal salts with sodium hydroxide in a mortar. This solvent free method is environment friendly and fast. This method could be extended to the preparation of Ni/Zn hydroxy double salts. The Ni/Zn ratio could be varied from 1.2 to 1.9 by varying the metal contents of the precursor salts without the formation of any impurities in the sample. The prepared compounds had similar characteristics as that of the samples prepared by precipitation route. No sign of carbonate contamination was observed in any of the prepared samples.

The selective intercalation of organic carboxylates and sulfonates into hydroxy double salts

This paper reports the first systematic investigation of the selectivity of organic guest intercalation into hydroxy double salts. The organic guests 1,2- and 1,4-benzenedicarboxylate (1,2- and 1,4-BDC) have been incorporated into a range of hydroxy double salts by anion exchange. Intercalates of [Zn5(OH)8](NO3)2·yH2O, [Zn5(OH)8]Cl2·yH2O, [Zn5(OH)8](CH3COO)2·yH2O, [Zn3Ni2(OH)8](NO3)2·yH2O, and [Zn3.8Co1.2(OH)8](NO3)2·yH2O were prepared, and the resultant materials fully characterized. 1,5- and 2,6-Napthalanedisulfonate (1,5- and 2,6-NDS) were also successfully intercalated into the [Zn5(OH)8](NO3)2·yH2O material. It was found that the initial anions are almost completely replaced by the new organic guests in the majority of cases. Selected reactions were investigated by in situ X-ray diffraction, and the reactions observed to proceed directly from the host to the product largely under nucleation control. No intermediate phases were detected. The competitive intercalation of isomeric pairs of guest anions was explored, and very high degrees of preferential intercalation found for 1,4- over 1,2-BDC into all hydroxy double salts (HDSs) studied, and for 2,6- over 1,5-NDS into [Zn5(OH)8](NO3)2·yH2O. The selectivity was found to be largely invariant with reaction time, reaction temperature, solvent system, and guest concentration. It was also observed to be very similar across all the HDSs explored. In situ diffraction and NMR demonstrate that the selective intercalation is a thermodynamically controlled phenomenon. It is therefore suggested that preferential intercalation is governed in the main by the strength of the interactions between the HDS layers and the guest ions.

Hydroxy double salts as versatile storage and delivery matrices

The utility of hydroxy double salts (HDSs) for the uptake and delivery of a range of functional anions via ion exchange is demonstrated. Three novel HDS nanocomposites containing medicinal (ibuprofen and diclofenac) and agrochemical (2,4,5-trichlorophenoxyacetic acid) species have been synthesised through ion exchange intercalation. The release of the guest ions from the host has subsequently been explored. A range of models have been applied to the release kinetics. Release of 2,4,5-trichlorophenoxyacetic acid took place over ca. 200 minutes and release of ibuprofen over around 250 minutes. Coating the crystallites of the intercalates with a sodium alginate layer led to release times being extended to approximately 10 hours, which is an appropriate timescale for an effective release system.

Hexacyanoferrate-intercalated nickel zinc hydroxy double salts

When anionic clay like nickel zinc hydroxyacetate was subjected to anion exchange reaction with either hexacyanoferrate(II) or hexacyanoferrate(III) ions, the complex anion intercalation was accompanied by auto redox reactions. In both the cases a mixture of hexacyanoferrate(II) and hexacyanoferrate(III) ions was found to be intercalated in the anionic clay. The mixed anion intercalated anionic clays could be oxidized by hydrogen peroxide to get pure hexacyanoferrate(III) intercalated anionic clay. Thermal decomposition of the intercalated anionic clays yields mixed oxides of Ni, Zn and Fe.

Creation of highly stable monomeric Pd(II) species in an anion-exchangeable hydroxy double salt interlayer: Application to aerobic alcohol oxidation under an air atmosphere

An active Pd(II) catalyst supported on the Ni–Zn mixed basic salt (NiZn), which is classified by the anion-exchangeable layered hydroxy double salts, was synthesized by simple intercalation of the anionic Pd(II) hydroxyl complex. The divalent Pd species in the interlayer of NiZn maintained their original monomeric structure during the aerobic alcohol oxidation, due to the strong electrostatic interaction between the NiZn host and anionic Pd(II) species. This catalyst could be reused without any loss of the catalytic activity and selectivity in the aerobic alcohol oxidation.

Layered nanomaterials for green materials

In this feature article, the applications of layered nanomaterials as green materials are demonstrated along with their structures and properties. Due to the unique 2-dimensional structures and biocompatibility, various eco- and bio-friendly materials can be hybridized with layered nanoparticles such as layered double hydroxides (LDHs), hydroxy double salts (HDSs) and cationic clays. From small molecules such as drugs, herbicides, fertilizers, and food ingredients to large substances like deoxyribonucelotides (DNA), protein, and enzymes, various functional materials can be incorporated into layered nanoparticles via intercalation reactions to produce green materials with versatile applications. The application fields of layered nanomaterials, especially LDHs, are summarized into three categories; biomolecule reservoir, pharmaceutical and other applications.

Thermal Degradation of Acetate-Intercalated Hydroxy Double and Layered Hydroxy Salts

Two hydroxy double salts (HDSs), zinc copper hydroxy acetate (ZCA) and zinc nickel hydroxy acetate (ZNA), and an analogous layered compound, zinc hydroxy acetate (ZHA), have been prepared by a coprecipitation method. The thermal degradation of these materials was characterized via thermogravimetric analysis (TGA), differential thermal analysis (DTA), and TGA coupled with Fourier transform infrared spectroscopy of gas-phase products, TGA-FTIR. Loss of physisorbed and interlayer H2O was observed between 50 and 150 degrees C for all compounds. Acetic acid, acetone, water, and CO2 were released at high temperatures with relative acetone yields found to be dependent on precursor identity, with very little formed from ZCA compared with ZHA and ZNA. Combined FTIR and XRD analysis of solid residues extracted at different points in the heating profile suggests that ketonization occurs via dissociative adsorption of acetic acid on ZnO surfaces. Nanometer-sized ZnO particles were formed from ZHA, showing slight preferential growth in the ZnO (002) lattice direction, while the presence of a second metal, Ni or Cu, served to retard ZnO crystallite growth at temperatures below 600 degrees C and eliminate preferential growth. ZCA leads to the formation of reduced copper species (metallic copper and Cu2O) when heated to 250 degrees C.

Hybrid organic–inorganic materials: Layered hydroxy double salts intercalated with substituted thiophene monomers

The present paper describes the synthesis and characterization of Layered Hydroxy Double Salts (HDSs) containing substituted thiophene anions (2-thiophenecarboxylate, 3-thiophenecarboxylate, and 3-thiopheneacetate). The HDSs host was synthesized via hydrothermal method and the organic anions were incorporated between the sheets by anion-exchange reaction. The materials were characterized by powder X-ray diffraction (PXRD), thermal gravimetric (TG) analysis and electron spin resonance (ESR) spectroscopy. For the 2D-hybrid materials, the basal spacing is found to be consistent with the formation of bilayers of the intercalated organic monomers. For the hybrid material formed after intercalation of 3-thiopheneacetate anion, the ESR signals suggest that the monomers connect each other directly forming small oligomers, whereas this process is not occurring for the two other monomers presenting short alkyl chain. The TG analyses show different stages of thermal decomposition between HDSs host and 2D-hybrid materials, underlining the enhanced thermal stability of the hybrid assembly.

Synthesis and Analysis of Copper Hydroxy Double Salts

An introductory chemistry project involving the synthesis and identification of double salts containing the copper and hydroxide ions is described. The preparations are carried out in aqueous solution and the analyses include qualitative, colorimetric, gravimetric, and volumetric gas analyses. The results permit the student to determine the empirical formula of the compound synthesized. The results can be discussed with regard to the conditions under which these minerals form in nature.

Hydroxy Double Salt Anion Exchange Kinetics: Effects of Precursor Structure and Anion Size

(1)H NMR spectroscopy and powder X-ray diffraction have been used to explore the details of anion exchange reactions of two layered hydroxy double salts (HDSs), zinc copper hydroxy acetate (ZCA), nickel zinc hydroxy acetate (NZA), and a related layered material, zinc hydroxy acetate (ZHA), at room temperature (21-22 degrees C). Reactions that followed Avrami-Erofe'ev kinetics with respect to temporal profiles for acetate release, ZCA with butyrate (k = 1.7 x 10(-3) s(-1)), and octanoate (k = 0.79 x 10(-3) s(-1)) anions, as well as ZHA with octanoate (k = 2.6 x 10(-3) s(-1)), demonstrate that rate constants for acetate release are influenced by the exchange anion relative size as well as by the solid precursor structure/composition. The reaction of NZA with octanoate deviated from expected Avrami-Erofe'ev behavior, with evidence for an intermediate species in the solid phase that may influence the rate of acetate release into solution. The reaction of ZCA with formate anions exhibited a unique zeroth-order kinetics release of acetate, providing the possibility of developing tunable nanostructured anion release sources by use of variations in the size of the exchange species.

Nanohybridization of Biomolecules with Layered Double Hydroxides and Hydroxy Double Salts for Advanced Applications

Nanohybridization of Biomolecules with Layered Double Hydroxides and Hydroxy Double Salts for Advanced Applications

Delamination–restacking behaviour of surfactant intercalated layered hydroxy double salts, M 3Zn 2(OH) 8(surf) 2⋅2H 2O [M = Ni, Co and surf = dodecyl sulphate (DS), dodecyl benzene sulphonate (DBS)

Surfactant anion intercalated nickel–zinc and cobalt–zinc layered hydroxy double salts were prepared through a modified acetate hydrolysis route. These organo-inorganic hybrids delaminate readily in alcohols such as 1-butanol to give stable translucent colloids. The extent of delamination and the stability of the colloids obtained are comparable to what has been observed in the case of layered double hydroxides (LDHs). The original layered solid could be obtained either by evaporation of the colloid or precipitation by the addition of a polar solvent such as acetone.