Divalent Metal Nitrates Research Articles

Microwave-assisted synthesis of ternary Li-M-Al LDHs (M = Mg, Co, Ni, Cu, Zn, and Cd) and examining their use in phenol oxidation

It remained challenging to synthesize Li and Al-containing ternary Li-M-Al layered double hydroxides (LDH) because LiI and other metal ions (MII or MIV) prefer different atomic positions, consequently making traditional methods such as co-precipitation or hydrothermal method fail. In the present work, several transition (Co, Ni, Cu) and non-transition (Mg, Zn, Cd) metal ions incorporated ternary Li-M-Al LDHs were synthesized by reacting LiAlH4 and different divalent metal nitrates under microwave-assisted hydrolysis reaction. The layer arrangement formation was verified from powder X-ray diffraction and SEM images, while the presence of three cations in all these samples was confirmed from ICP-AES measurements. FTIR and Raman spectra of these samples confirmed the nitrate anion's (majorly) presence in the interlayer space and the fingerprint bands due to the hydroxide units. The thermal traces contained a two-step dehydroxylation, suggestive of the existence of three cations in the hydroxide layers. Isothermal magnetization of ternary LDH containing Co, Ni, and Cu showed paramagnetic behavior at room temperature. On calcination, α-LiAlO2 and other metal oxides were formed. All the ternary Li-M-Al LDHs (M = Mg, Co, Ni, Cu, Zn, and Cd) were examined as catalysts for the oxidative degradation of phenol, a well-known toxic pollutant. Only Li-Cu-Al LDH displayed high catalytic activity for phenol oxidation. p-benzoquinone formed from phenol initially (60 min) and degraded completely into oxalic acid, maleic acid, and fumaric acid after 120 min, as determined by UV–visible and GC-HRMS measurements.

Ab Initio Molecular Dynamics Study of Aqueous Solutions of Magnesium and Calcium Nitrates: Hydration Shell Structure, Dynamics and Vibrational Echo Spectroscopy.

Ab initio molecular dynamics simulations are performed to study the hydration shell structure, dynamics, and vibrational echo spectroscopy of aqueous Mg(NO3)2 and Ca(NO3)2 solutions. The hydration shell structure is probed through calculations of various ion-ion and ion-water radial and spatial distribution functions. On the dynamical side, calculations have been made for the hydrogen bond dynamics of hydration shells and also residence dynamics and lifetimes of water in different solvation environments. Subsequently, we looked at the dynamics of frequency fluctuations of OD modes of heavy water in different hydration environments. Specifically, the temporal decay of spectral observables of two-dimensional infrared (2DIR) spectroscopy, three pulse echo peak shift (3PEPS) measurements and also of time correlations of frequency fluctuations are calculated to investigate the dynamics of vibrational spectral diffusion of water in different hydration environments in these solutions. The OD stretch frequencies of water molecules in the vicinity of both divalent cations are found to be red-shifted and also fluctuating at a slower rate than other water molecules present in the solutions. The Mg2+ ions are found to be strongly hydrated which can be linked to their lower tendency to form contact ion-pairs and essentially no water exchange between the cationic hydration shells and bulk during the time scale of the current simulations. The stronger hydration of Mg2+ ions make their hydration shells structurally and dynamically more rigid and make the dynamics of hydrogen bonds and vibrational spectral diffusion, as revealed through spectral observables of 2DIR and 3PEPS slower than that for the Ca2+ ions. The structural and spectral dynamics of water molecules outside the cationic solvation shells in the Mg(NO3)2 solution are also found to be relatively slower than that of the Ca(NO3)2 solution and pure water which show the effects of stronger electric fields of Mg2+ ions extending beyond their first hydration shells. Also, water molecules in the hydration shells of the NO3- ions are found to relax at a slower rate in the Mg(NO3)2 solution which manifests the effect countercations have on anionic hydration shells for divalent metal nitrate solutions.

Crystal structures with infinite chains based on antimony tartrate dimers

Abstract Seven complex metal antimony tartrates have been synthesized in single crystal form by slowly evaporating aqueous solutions of potassium antimony tartrate (tartar emetic) and divalent metal nitrates or perchlorates. Crystal structures of these compounds all contain infinite chains formed by linking antimony tartrate dimers with divalent metal ions. While infinite chains of antimony tartrate dimers bridged by single Zn2+ ions or by double Mg2+ ions were reported previously, new types of chains with alternating single and double bridging cations are observed in this work.

Tuning the nano-porosity and nano-morphology of nano-filtration (NF) membranes: Divalent metal nitrates modulated inter-facial polymerization

Divalent metal nitrates were pre-loaded on polysulfone support to modulate the interfacial polymerization between piperazine (PIP) and trimesoyl chloride (TMC). It is found that the nano-porosity and nano-morphology of thus formed thin film composite polyamide (TFC-PA) nano-filtration (NF) membranes as well as their filtration performance could be effectively tuned by the type and concentration of the divalent metal salts, especially the divalent cations used. Main group cations, such as Mg (II) and Ca (II), increased the water flux of the NF membranes by increasing their surface nano-scale nodular arrays without altering the pore sizes and rejections of the membranes, while transitional metal cations such as Zn (II), Cu (II) and Co (II) increased the water flux of the NF membranes not only by the formation of high surface area nano-scale Turing type crisscrossed ridge networks, but also by the increase of their nano-pore sizes due to their coordination with the >NH groups of the PIP. The prepared NF membranes pore sizes adjustable from 0.54 Å to 0.90 Å could be developed to have varied selectivity and rejections among inorganic salts and organic dyes.

Structural, spectroscopic insights, and antimicrobial properties of mononuclear and dinuclear metal(II) carboxylate derivatives with metronidazole

A dinuclear paddle-wheel complex [Cu2(PTA)4(mnz)2] (1) and mononuclear [M(BBA)2(mnz)2(H2O)2] complexes, where PTA = p-methylbenzoate, BBA = 2-bromobenzoate, mnz = metronidazole and M = Cu(II) (2), Co(II) (3), Ni(II) (4), Zn(II) (5), Cd(II) (6) were prepared by adding metronidazole to the mixture of divalent metal nitrate salts and arylcarboxylate acid in alkaline aqueous solution under ambient conditions. The complexes were characterized by elemental analysis, spectroscopy (FTIR, UV–visible and NIR-Vis-UV), single crystal X-ray diffraction (SCXRD), Hirshfeld surface analysis and High-Field EPR. The asymmetry of the d − d bands observed in the electronic diffuse − reflectance spectra of cobalt(II) and nickel(II) complexes is due to the symmetry lowering from Oh to elongated D4h in trans − [MN2O2O2′] chromophores. Large zero-field splitting was observed in the HF EPR spectra of the Ni(II) and Co(II) complexes which was modeled by using the CASSCF method. The antimicrobial activity was studied using the agar well diffusion method. The antimicrobial tests of these new compounds were carried out on Candida albicans and five bacterial strains (three Gram-negative and two Gram-positive), and were compared to their respective parent ligands. A broad antimicrobial spectrum was observed in some of the complexes.

Preferential solvation, ion pairing, and dynamics of concentrated aqueous solutions of divalent metal nitrate salts.

We have investigated the characteristics of preferential solvation of ions, structure of solvation shells, ion pairing, and dynamics of aqueous solutions of divalent alkaline-earth metal nitrate salts at varying concentration by means of molecular dynamics simulations. Hydration shell structures and the extent of preferential solvation of the metal and nitrate ions in the solutions are investigated through calculations of radial distribution functions, tetrahedral ordering, and also spatial distribution functions. The Mg2+ ions are found to form solvent separated ion-pairs while the Ca2+ and Sr2+ ions form contact ion pairs with the nitrate ions. These findings are further corroborated by excess coordination numbers calculated through Kirkwood-Buff G factors for different ion-ion and ion-water pairs. The ion-pairing propensity is found to be in the order of Mg(NO3)2 < Ca(NO3)2 < Sr(NO3)2, and it follows the trend given by experimental activity coefficients. It is found that proper modeling of these solutions requires the inclusion of electronic polarization of the ions which is achieved in the current study through electronic continuum correction force fields. A detailed analysis of the effects of ion-pairs on the structure and dynamics of water around the hydrated ions is done through classification of water into different subspecies based on their locations around the cations or anions only or bridged between them. We have looked at the diffusion coefficients, relaxation of orientational correlation functions, and also the residence times of different subspecies of water to explore the dynamics of water in different structural environments in the solutions. The current results show that the water molecules are incorporated into fairly well-structured hydration shells of the ions, thus decreasing the single-particle diffusivities and increasing the orientational relaxation times of water with an increase in salt concentration. The different structural motifs also lead to the presence of substantial dynamical heterogeneity in these solutions of strongly interacting ions. The current study helps us to understand the molecular details of hydration structure, ion pairing, and dynamics of water in the solvation shells and also of ion diffusion in aqueous solutions of divalent metal nitrate salts.

Structurally diverse divalent metal pyromellitate coordination polymers with very long spanning dipyridylamide ligands

Hydrothermal reaction of divalent metal nitrates, pyromellitic acid (pymH4), and either 1,6-hexanediaminebis(nicotinamide) (hbn) or 1,6-hexanediaminebis(isonicotinamide) (hbin) afforded crystalline coordination polymers whose dimensionality depends synergistically on the dipyridylamide nitrogen donor disposition and metal coordination environment. These new phases were structurally characterized via single-crystal X-ray diffraction. [Cd(pymH2)(hbn)(H2O)2]n (1) and [Co(pymH2)(hbn)(H2O)2]n (2) display isostructural (4,4) grid topologies with [M(pymH2)(H2O)2]n chains pillared by hbn ligands. {[Cu2(pym)(hbn)(H2O)2]·2H2O}n (3) manifests a 3D 3,4-connected network with a rare (83)2(86) topology built from the hbn pillaring of [Cu2(pym)(H2O)]n layer motifs. {[Zn2(pym)(hbin)2(H2O)]·H2O}n (4) shows a 1D ribbon motif based on [Zn2(OCCCCO)2] 14-membered circuits. {[Ni2(pym)(hbin)(H2O)4]·3H2O}n (5) exhibits 3,4-connected layer motifs with rare {4.62}2{426282} topology. Luminescent behavior in 1 and 4 is ascribed to intra-ligand molecular orbital transitions. These phases were also surveyed for the ability to detect nitrobenzene in ethanol suspension. Thermal decomposition behavior of 1–5 is also discussed herein.

Effect of substituent on dimensionality and properties in divalent metal isophthalate coordination polymers with a conformationally flexible dipyridylamide coligand

Hydrothermal reaction of divalent metal nitrates and 3-pyridylmethylnicotinamide (3-pmna) with either isophthalic acid (H2iph) or 5-nitroisophthalic acid (H2nip) has afforded a series of four coordination polymer solids that were structurally characterized via single-crystal X-ray crystallography. [Ni(iph)(3-pmna)]n (1) and [Cd(iph)(3-pmna)]n (2) both exhibit a {M2(OCO)2} dimer-based 1-D ribbon topology with metal–metal contacts bridged by both ip and 3-pmna ligands. [Ni(nip)(3-pmna)]n (3) has the same topology as its unsubstituted congener 1, showing a null effect on the part of the nip nitro group. On the other hand [Cd(nip)(3-pmna)]n (4) exhibits a {Cd2O2} dimer-based 2-D (4,4) layer topology, a rare example of the nitro group imposing a higher dimensionality in the resulting coordination polymer. While 2 showed strong blue–violet luminescence, quenching mechanisms due to the nitro group rendered 4 non-luminescent. Thermal properties of these new materials are also investigated.

Studies of LiNi2 / 3Mn1 / 3O2: A Positive Electrode Material That Cycles Well to 4.6 V

was synthesized from and mixed hydroxide. Four different coprecipitation routes were used to prepare the precursor beginning with divalent metal nitrates or metal sulfates. When ammonia was added during the coprecipitation under anaerobic conditions, spherical and dense particles of were prepared. The impact of various coprecipitation methods on the subsequent properties of was studied by X-ray diffraction (XRD), scanning electron microscopy (SEM), and electrochemical tests. Spherical and dense particles of showed an excellent charge–discharge cycle life at 4.6 V. The impact of heating temperature and time on the properties of was also studied by XRD, SEM, and electrochemical tests and suggested that the heating temperature plays a significant role in determining the electrochemical performance of . Accelerating rate calorimetry results suggest that is less thermally stable than .

The role of deprotonation of the ligand on the structures of metal phosphonates: synthesis, characterization and crystal structures of two new metal diphosphonates with a 1D double chain and a 2D layer structure

Reactions of N-methyl-iminobis(methylenephosphonic acid), CH3N(CH2PO3H2)2, (H4L) with divalent metal nitrates in aqueous solution afforded two new metal diphosphonates with different structures. Zn(H2L)(H2O) (1) features a 1D double chain built from ZnO4 tetrahedra cross-linked by bridging phosphonate groups and ligands. Each zinc cation is tetrahedrally coordinated by three phosphonate oxygen atoms from three ligands and an aqua ligand. These double chains are interconnected into a layer through N–H⋯O and O–H⋯O hydrogen bonds. In Cd(H3L)2·2H2O (2) the Cd(II) ion is octahedrally coordinated by six phosphonate oxygen atoms from four ligands, two of them in a bidentate and two in a unidentate fashion. Each CdO6 octahedron is further linked to four neighboring CdO6 octahedra through four bridging phosphonate groups, resulting in a two-dimensional metal phosphonate (002) layer. These layers are held together by strong hydrogen bonds between uncoordinated phosphonate oxygen atoms. The effect of the extent of deprotonation of phosphonic acids on the type of complex formed is discussed.

Preparation of fine particle chromites: A combustion approach

Fine particle metal chromites, MCr 2O 4 where M = Mg, Mn, Fe, Co, Ni, Cu and Zn have been obtained by the combustion of a redox mixture containing corresponding divalent metal nitrate, chromium (III) nitrate and tetraformal trisazine (TFTA). An aqueous saturated solution of the redox mixture when rapidly heated at 350°C boils, foams and ignites to yield voluminous, fine particle chromite powder. Formation of chromite was confirmed by X-ray diffraction pattern and IR spectra. Fine particle nature of chromites was studied using particle size analysis, surface area measurements, TEM and SEM. The particle size of chromites is below lum and the surface area ranges from 13 to 30 m 2/g.

Far infrared spectra of complexes of pyridine with some divalent metal nitrates

The far i.r. spectra of the complexes NiII, CoII, CuII and ZnII(py)x(NO3)2 have been obtained with a view to determining which of the previously reported stoicheiometries exist. The results allow identification of M(py)x-(NO3)2(M = Ni, Co; x= 3, 6), Cu(py)x(NO2)2(x= 2, 3, 4, 6), and Zn(py)x(NO3)2(x= 2, 3, 6) as distinct phases.

Vibrational Spectra of Molten Salts. II. Infrared Spectra of Some Divalent Metal Nitrates in Alkali-Metal Nitrate Solutions

Infrared spectra of thin films of Mg(NO3)2, Sr(NO3)2, Ba(NO3)2, Cd(NO3)2, and Pb(NO3)2, in molten KNO3 and equimolar KNO3–NaNO3 mixtures have been obtained over the spectral region 4000–200 cm−1. All the nitrates except those of Mg and Cd were in the anhydrous state. Even at temperatures of 300°C or more, the magnesium and cadmium nitrate melts retained small amounts of water. As the concentrations of the divalent metal nitrates were increased, some nitrate bands split, and new low-frequency lines were observed in some cases. These are located at 380 and 340 cm−1 for Mg(NO3)2 solutions, at 520 cm−1 for Cd(NO3)2, and around 420 cm−1 for Pb(NO3)2. The splitting of the ν3 line of free nitrate decreases in the order Mg2+&amp;gt;Cd2+&amp;gt;Ca2+&amp;gt;Pb2+&amp;gt;Sr2+&amp;gt;Ba2+. Except for Sr2+, this is the order of the ionic potentials. The observed bands are assigned and discussed in terms of complexes formed between metal and nitrate ions. Relative strengths of nitrate and chloride binding by Cd2+ and Mg2+ ions have been investigated by addition of Cl− ion to the mixed nitrate systems.