Perchlorate Hexahydrate Research Articles

Synthesis, structural characterization and DFT calculation on a square-planar Ni(II) complex of a compartmental Schiff base ligand

Reaction of a symmetric compartmental Schiff-base ligand, (H2L) with nickel(II) perchlorate hexahydrate in 1:1 M ratio in methanol gives rise to a mononuclear nickel(II) compound, NiL (1). The compound has been characterized by C, H, N microanalyses and UV–Vis spectra. The single crystal X-ray diffraction studies reveal a square planar geometry around the Ni(II) center. The compound crystallizes in monoclinic system with space group C2/c with a = 21.6425(6), b = 9.9481(3), c = 13.1958(4) Å, β = 107.728(2)°, V = 2706.16(14) Å3 and Z = 4. Ground state DFT optimization and TDDFT calculations on the ligand and complex were performed to get their UV–Vis spectral pattern.

Oximato-bridged copper(II) compounds: syntheses, molecular structures, magnetic, thermal and spectroscopic properties

Reaction of the Schiff base, 1-(4-methylimidazol-5-yl) phenylhydrazonopropane-2-one oxime (LH), with copper(II) perchlorate hexahydrate and copper(II) nitrate trihydrate in a 1 : 1 M proportion in methanol affords [Cu2L2(H2O)(ClO4)](ClO4) (1) and [Cu2L2(H2O)2](NO3)2] (2) in moderate yields. Both 1 and 2 have been characterized by elemental analysis, ESI-MS, FT-IR, UV–vis absorption spectroscopy, EPR, electric conductivity, and magnetic susceptibility measurements. The X-ray crystal structures of 1·CH3COCH3 and 2 have been determined. Both compounds are dinuclear copper(II) complexes, with each copper μ2-bridged by two oxime ligands in a μ2-η1,η2 fashion. Variable temperature magnetic studies on 1 and 2 show that both compounds are dominated by an antiferromagnetic coupling through the oxime bridges.

EFFECT OF PERCHLORATES ON ELECTRON RADIOLYSIS OF GLYCINE WITH APPLICATION TO MARS

ABSTRACT This work explores the radiolytic decomposition of glycine (H2NCH2COOH) under simulated Martian conditions in the presence of perchlorates ( ), which are abundant oxidizers on the surface of Mars, by energetic electrons at 10, 160, 210, and 260 K, mimicking the radiation exposure of the Martian regolith in the first 5–10 cm depths over about 250 million years. Our experiments present quantitative evidence that the rate constants of the glycine decomposition in the presence of magnesium perchlorate hexahydrate (Mg(ClO4)2 · 6H2O) were a factor of about two higher than that of the pure glycine, suggesting that energetic oxygen atoms (O) released from the have a significant effect on the decomposition rates and accelerate them by providing a unique oxidizing environment in the radiolyzed samples. Hence, two decay mechanisms exist: radiolysis by the electrons and oxidation by the O atoms. Within the Mars-relevant temperature range covering 160–260 K, the destruction rates are nearly temperature invariant with rates varying as little as 5%. Further, the formation rates of carbon dioxide (CO2) and carbon monoxide (CO) are both accelerated in the presence of by a factor of three to five, supporting our conclusion of an active oxygen-initiated chemistry. In addition, the degradation rates are significantly higher than the formation rates of CO2 and CO. This suggests that, besides the decarboxylation, alternative degradation pathways such as a polymerization of glycine must exist. Finally, besides CO2 and CO, three alternative products were identified tentatively: methylamine (CH3NH2), methane (CH4), and ammonia (NH3).

MECHANISTIC STUDIES ON THE RADIOLYTIC DECOMPOSITION OF PERCHLORATES ON THE MARTIAN SURFACE

ABSTRACT Perchlorates—inorganic compounds carrying the perchlorate ion ( ClO 4 − ?> )—were discovered at the north polar landing site of the Phoenix spacecraft and at the southern equatorial landing site of the Curiosity Rover within the Martian soil at levels of 0.4–0.6 wt%. This study explores in laboratory experiments the temperature-dependent decomposition mechanisms of hydrated perchlorates—namely magnesium perchlorate hexahydrate (Mg(ClO4)2·6H2O)—and provides yields of the oxygen-bearing species formed in these processes at Mars-relevant surface temperatures from 165 to 310 K in the presence of galactic cosmic-ray particles (GCRs). Our experiments reveal that the response of the perchlorates to the energetic electrons is dictated by the destruction of the perchlorate ion ( ClO 4 − ?> ) and the inherent formation of chlorates ( ClO 3 − ?> ) plus atomic oxygen (O). Isotopic substitution experiments reveal that the oxygen is released solely from the perchlorate ion and not from the water of hydration (H2O). As the mass spectrometer detects only molecular oxygen (O2) and no atomic oxygen (O), atomic oxygen recombines to molecular oxygen within the perchlorates, with the overall yield of molecular oxygen increasing as the temperature drops from 260 to 160 K. Absolute destruction rates and formation yields of oxygen are provided for the planetary modeling community.

Synthetic, structural, electrochemical and DNA-binding aspects of a novel oximato bridged copper(II) dimer

A dimeric double oximato-bridged (μ1,2-N-O) Cu(II) complex, [Cu2L2(ClO4)2]·2H2O (1), was synthesized from the reaction of equimolar proportion of a novel Schiff base ligand, 1-phenyl-1-(pyridin-2-yl-hydrazono)-propan-2-one oxime (LH), and copper(II)perchlorate hexahydrate in methanol. C, H and N microanalyses, gravimetric copper estimation, FT-IR, UV–Vis (solid state as well as in solution), ESI-MS spectra, molar electric conductivity, EPR and room temperature magnetic susceptibility measurements were performed to characterize 1. The X-ray crystal structure of 1 shows that each copper center in 1 is in ‘N3O2’ coordination environment with a Cu⋯Cu separation of 3.595Å. 1 follows unique two-step mono-electronic oxidative steps in its CV in methanol. ESI-MS spectrum of 1 indicates that the dimeric core unit retains its identity in solution as well. Interaction of 1 with Calf thymus (CT) DNA was studied by spectroscopic and calorimetric techniques. The mode of binding was investigated by ethidium bromide displacement assay. This binding enhanced the stabilization of the DNA structure against thermal strand separation. The magnitudes of the association constant as derived from spectroscopic and calorimetric studies are in good harmony.

Laboratory investigation of perchlorate deliquescence at the surface of Mars with a Raman scattering lidar

AbstractA sample of magnesium perchlorate hexahydrate was subjected to the water vapor pressure and temperatures found at the landing site of the Phoenix Mars mission. Laser Raman scattering was applied to detect the onset of deliquescence and provide a relative estimate of the quantity of water taken up and subsequently released by the sample. As the temperature of the sample decreased at the same rate as measured on Mars during the evening, significant uptake of water from the atmosphere was observed to occur prior to the frost point temperature being reached. As the temperature was lowered further, the relative humidity over ice increased to 100% and frost formed on the surface surrounding the perchlorate sample. Freezing of the brine film was observed at the eutectic temperature of −67°C, and thawing occurred at a temperature of −62°C.

Spontaneous Resolution Induced by a Chiral Ni(II) Complex with an Achiral Tripodal Ligand#

A chiral nickel(II) complex, [Ni(II)H3L](ClO4)2 (1), with an achiral ligand H3L (=tris{2‐(4‐imidazolyl)methyliminoethyl}amine) was synthesized by in situ reaction between nickel(II) perchlorate hexahydrate and a condensation mixture of 4‐imidazolecarboxaldehyde and tris(2‐aminoethyl)amine. Single crystal X‐ray analysis revealed that the H3L ligand hexadentately binds to Ni(II) ion through three Schiff‐base imine N atoms and three imidazole N atoms with distorted octahedral geometry. Both single‐crystal X‐ray diffraction and circular dichroism investigations found that the crystal of complex 1 was an enantiopure conglomerate. The hydrogen‐bond network of NimidazoleH⋯OClO4⋯HNimidazole induced spontaneous resolution to form the conglomerate. The capped tripod‐shaped [Ni(II)H3L]2+ complex ions are hydrogen‐bonded in a tail‐to‐tail mode and array in an up‐and‐down manner repeatedly to honeycomb an extended two‐dimensional homochiral network with trigonal voids.

Cu(ClO4)2·6H2O catalyzed solvent free per-O-acetylation and sequential one-pot conversions of sugars to thioglycosides

The solvent free per-O-acetylation of various reducing and non-reducing sugars has been carried out using stoichiometric amounts of acetic anhydride and copper(ii) perchlorate hexahydrate as the catalyst.

Unprecedented structural variations in trinuclear mixed valence Co(II/III) complexes: theoretical studies, pnicogen bonding interactions and catecholase-like activities.

Three new mixed valence trinuclear Co(II/III) compounds cis-[Co3L2(MeOH)2(N3)2(μ1,1-N3)2] (1), trans-[Co3L2(H2O)2(N3)2(μ1,1-N3)2]·(H2O)2 (2) and [Co3L(R)2(N3)3(μ1,3-N3)] (3) have been synthesized by reacting a di-Schiff base ligand (H2L) or its reduced form [H2LR] (where H2L= N,N'-bis(salicylidene)-1,3-propanediamine and H2LR= N,N'-bis(2-hydroxybenzyl)-1,3-propanediamine) with cobalt perchlorate hexahydrate and sodium azide. All three products have been characterized by IR, UV-Vis and EPR spectroscopies, ESI-MS, elemental, powder and single crystal X-ray diffraction analyses. Complex 2 is an angular trinuclear species in which two terminal octahedral Co(III)N2O4 centers coordinate to the central octahedral cobalt(II) ion through μ2-phenoxido oxygen and μ1,1-azido nitrogen atoms along with two mutually cis-oxygen atoms of methanol molecules. On the other hand, in linear trinuclear complex , in addition to the μ2-phenoxido and μ1,1-azido bridges with terminal octahedral Co(III) centres, the central Co(II) is bonded with two mutually trans-oxygen atoms of water molecules. Thus the cis-trans configuration of the central Co(II) is solvent dependent. In complex 3, the two terminal octahedral Co(III)N2O4 centers coordinate to the central penta-coordinated Co(II) ion through double phenoxido bridges along with the nitrogen atom of a terminal azido ligand. In addition, the two terminal Co(III) are connected through a μ1,3-azido bridge that participates in pnicogen bonding interactions (intermolecular N-N interaction) as an acceptor. Both the cis and trans isomeric forms of 1 and 2 have been optimized using density functional theory (DFT) calculations and it is found that the cis configuration is energetically more favorable than the trans one. However, the trans configuration of 2 is stabilized by the hydrogen bonding network involving a water dimer. The pnicogen bonding interactions have been demonstrated using MEP surfaces and CSD search which support the counter intuitive electron acceptor ability of the μ1,3-azido ligand. Complexes 1-3 exhibit catecholase-like activities in the aerial oxidation of 3,5-di-tert-butylcatechol to the corresponding o-quinone. Kinetic data analyses of this oxidation reaction in acetonitrile reveal that the catecholase-like activity follows the order: 1 (kcat = 142 h(-1)) > 3 (kcat = 99 h(-1)) > 2 (kcat = 85 h(-1)). Mechanistic investigations of the catalytic behaviors by X-band EPR spectroscopy and estimation of hydrogen peroxide formation indicate that the oxidation reaction proceeds through the reduction of Co(III) to Co(II).

Crystal structures of Ca(ClO4)2·4H2O and Ca(ClO4)2·6H2O.

The title compounds, calcium perchlorate tetra-hydrate and calcium perchlorate hexa-hydrate, were crystallized at low temperatures according to the solid-liquid phase diagram. The structure of the tetra-hydrate consists of one Ca(2+) cation eightfold coordinated in a square-anti-prismatic fashion by four water mol-ecules and four O atoms of four perchlorate tetra-hedra, forming chains parallel to [01-1] by sharing corners of the ClO4 tetra-hedra. The structure of the hexa-hydrate contains two different Ca(2+) cations, each coordinated by six water mol-ecules and two O atoms of two perchlorate tetra-hedra, forming [Ca(H2O)6(ClO4)]2 dimers by sharing two ClO4 tetra-hedra. The dimers are arranged in sheets parallel (001) and alternate with layers of non-coordinating ClO4 tetra-hedra. O-H⋯O hydrogen bonds between the water mol-ecules as donor and ClO4 tetra-hedra and water mol-ecules as acceptor groups lead to the formation of a three-dimensional network in the two structures. Ca(ClO4)2·6H2O was refined as a two-component inversion twin, with an approximate twin component ratio of 1:1 in each of the two structures.

Copper‐Catalyzed Oxidative Transformation of Secondary Alcohols to 1,5‐Disubstituted Tetrazoles

AbstractA mild and convenient oxidative transformation of secondary alcohols to 1,5‐disubstituted tetrazoles is uncovered by employing trimethylsilyl azide (TMSN3) as a nitrogen source in the presence of a catalytic amount of copper(II) perchlorate hexahydrate [Cu(ClO4)2.6 H2O] (5 mol%) and 2,3‐dichloro‐5,6‐dicyano‐para‐benzoquinone (DDQ) (1.2 equiv.) as an oxidant. This reaction is performed under ambient conditions and proceeds through CC bond cleavage.magnified image

Azide/thiocyanate incorporated cobalt(III)-Schiff base complexes: Characterizations and catalytic activity in aerobic epoxidation of olefins

Reaction of cobalt(II) perchlorate hexahydrate with a potentially tetradentate Schiff base ligand, HL (2-methoxy-6-[(2-diethylaminoethylimino)methyl]phenol) in presence of sodium azide and sodium thiocyanate yields two complexes [Co(L)(HL)(N3)]·ClO4 (1) and [Co(L)(HL)(NCS)]·ClO4 (2); both being characterized by different physicochemical methods. Crystal structure of 1 was determined by single crystal X-ray diffraction while that of 2 was reported earlier. In 1, the central cobalt(III) adopts slightly distorted octahedral geometry with same donor set to that of 2. Catalytic efficacy of the complexes towards epoxidation of different alkenes under aerobic condition were investigated in homogeneous medium which reveals that 1 is better catalyst than 2 with respect to alkene oxidation, reflected from the turn over frequencies (TOF) measured at an optimum temperature of 60°C in acetonitrile.

Mononuclear complexes and a coordination polymer of the 2-pyridylamino (NH2Py) functionalized P(v) ligand

Three mononuclear metal complexes, [{PO2(NH2Py)2}2M] [2Py = 2-pyridyl; M = Zn (1), Ni (2), Co (3)], have been synthesized by reacting metal nitrates with tetrakis(2-pyridylamino)phosphonium chloride, [P(NH2Py)4]Cl, under solvothermal reaction conditions. The ligand, [P(NH2Py)4]Cl, is hydrolyzed in the reaction medium. All of the complexes are isostructural and show an octahedral geometry around the metal ion. A coordination polymer, [{P(NH2Py)4Cu2Cl4}ClO4]∞ (4), was also obtained by treating [P(NH2Py)4]Cl with copper perchlorate hexahydrate at ambient temperature. All of the complexes were characterized by standard analytical techniques. The solid-state structures of 1–4 were established by single crystal X-ray diffraction analysis. The optical properties of 1–4 have been investigated.

Copper(II) thiocyanate complexes of 2-(2-pyridinyl)-benzthiazole: synthesis, structure, redox behavior, thermal aspects, and DFT calculations

Reaction of 2-(2-pyridinyl)-benzthiazole (Pbt), KSCN, and copper(II)perchlorate hexahydrate in 1 : 2 : 1 molar proportion in dimethyl sulfoxide gives monomeric [Cu(Pbt)(SCN)2DMSO] (1a). In another run, identical proportions of the same reactants in methanol generates a symmetric thiocyanate bridged dimeric copper(II) compound, [Cu2(Pbt)2(SCN)2] (2a), in 72% yield. Both 1a and 2a have been characterized by C, H, and N microanalyses, copper estimation, FTIR, UV–vis spectra, and room temperature magnetic susceptibility measurements. The X-ray crystal structures of 1a and 2a have been determined. Electrochemical studies of 1a and 2a show Cu(II) to Cu(III) oxidation in solution. The thermal behaviors of 1a and 2a have been studied. Bond valence sum method of analysis was performed to assign the oxidation state for each copper center in 1a and 2a. Geometry optimization of 1a, 2a, and their linkage isomers has also been performed at the level of the density functional theory to show that 1a and 2a are the most stable congeners. These results corroborate our experimental findings.

Structural Stability of Si–C Bonds in Periodic Mesoporous Thiophene-Silicas Prepared under Acidic Conditions

Periodic mesoporous thiophene-silicas with hexagonal (p6mm) symmetry were synthesized using a 2,5-bis(triethoxysilyl)thiophene (BTET) precursor in the presence of Pluronic P123 (EO20PO70EO20) and PLGE (EO17(L28G7)EO17) triblock copolymers at different acidic conditions. P123-templated mesoporous thiophene-silicas with p6mm ordered structure were prepared in the presence of hydrochloric acid and iron(III) chloride hexahydrate used as acid catalysts. However, it was found that a relatively large fraction of the Si–C bonds in thiophene-bridging groups were decomposed during the synthesis process. On the other hand, thiophene-silicas synthesized at lower acidic conditions were disordered and nonporous structures. In contrast, PLGE-templated thiophene-silicas with p6mm ordered mesostructure were prepared using copper(II) perchlorate hexahydrate and boric acid as well as hydrochloric acid. Importantly, up to 97.3% of the Si–C bonds in mesoporous thiophene-silica prepared in the presence of boric acid were retained. Solid state 29Si MAS NMR clearly showed that the structural stability of the Si–C bond is dependent on the acidity and time of the initial self-assembly stage. Also, the thermal stability of the thiophene-bridging groups was shown to be dependent on the acidity of the synthesis gel.

A linear S-bridged trinuclear cobalt(III) complex with 2-aminobenzenethiol: synthesis, crystal structure, and spectroscopic characterization

Treatment of cobalt(II) perchlorate hexahydrate with 2 M equiv. of 2-aminobenzenethiol (Habt) in acetonitrile afforded a tricationic tricobalt complex, [Co{Co(abt)3}2](ClO4)3·2CH3CN, by aerial oxidation. The molecular structure of the meso (ΔΛ) form of the complex was determined by X-ray crystallography. In the complex cation, the central Co is coordinated by six thiolate groups from two terminal fac(S)-[Co(abt)3] units in an octahedral geometry, forming a linear S-bridged tricobalt structure.

Proton‐Conducting Supramolecular Metallogels from the Lowest Molecular Weight Assembler Ligand: A Quote for Simplicity

Oxalic acid has been proven to be the lowest molecular weight organic ligand able to form robust supramolecular metallogel networks in the presence of metal salts. In particular, two novel multifunctional metallogels were readily prepared at room temperature by simple mixing of stock solutions of Cu(II) acetate monohydrate or Cu(II) perchlorate hexahydrate and oxalic acid dihydrate. Formation of different polymorphs and unprecedented proton conduction under anhydrous conditions were also demonstrated with some of these materials.

Synthesis, Spectral, Electrochemical, Magnetic and Biological Studies of Tet-A Based Binuclear Mn(III) Complexes

A new phenoxo-bridged Tet-a based binuclear manganese(III) complexes were synthesized by the Schiff base condensation reaction of the compound 1,8–[bis(3-formyl-2-hydroxy-5-methyl)benzyl] -5,5,7,12,12,14- hexamethyl -l,4,8,11-tetraazacyclotetradecane (PC–a) and 1,8– [bis(3-formyl-2-hydroxy-5-bromo)benzyl]- 5,5,7,12,12,14-hexamethyl-l,4,8,11-tetraazacyclotetradecane (PC–b) with triethylenetetramine and manganese(II) perchlorate hexahydrate. Their synthesized complexes were confirmed by analytical and spectral analysis. The phenolate oxygen atom is acting as bridge between two unsymmetrically coordinated Mn atoms. Electrochemical studies of the complexes reveal that all the redox processes are irreversible in nature. Low temperature magnetic study shows that the complexes exhibit antiferromagnetic exchange interaction between the two metal ions. The spectral and magnetic behavior of the complexes is discussed.

Anion-dependent complexation of 2-amino-benzothiazole and 2-imino-3-allyl-benzothiazole with Cu+: synthesis and characterization of [Cu(η 2-C10H10SN2)(C7H6SN2)NO3] and [Cu(C7H6SN2)2]ClO4

Interaction of 2-amino-benzothiazole with allyl chloride in ethanol resulted in a mixture of 2-imino-3-allyl-benzothiazole and unreacted 2-amino-benzothiazole. Using such a mixture and copper(II) nitrate trihydrate in ethanol – acetonitrile and alternating-current electrochemical technique, crystals of [Cu(η 2-C10H10SN2)(C7H6SN2)NO3] (1) π-complex, containing 2-imino-3-allyl-benzothiazole and 2-amino-benzothiazole coordinated to copper, have been obtained. The same procedure, starting from copper(II) perchlorate hexahydrate, performed in ethanol, led to formation of [Cu(C7H6SN2)2]ClO4 (2) σ-compound. Both compounds were structurally characterized. In the structure 1, 2-imino-3-allyl-benzothiazole is a chelate, bound to metal by C=C-bond of the allyl and nitrogen of the imino group. Another nitrogen from the thiazole core of 2-amino-benzothiazole and oxygen from complete a distorted trigonal-pyramidal environment of copper. [Cu(η 2-C10H10SN2)(C7H6SN2)NO3] building blocks are interconnected into infinite chains via N–H···O () hydrogen bonds and further linked into 3-D structure via π–π stacking between benzothiazole cores. In 2, Cu+ coordinates two nitrogens from two 2-amino-benzothiazoles, whereas locates outside the coordination sphere, fixed in space by N–H···O hydrogen bonds, which form puckered ribbons.

Oximato bridged dinuclear copper(II) complexes: Synthesis, crystal structure, magnetic, thermal, electrochemical aspects and BVS analysis

Reactions of the Schiff-base ligand, 2-hydroxyimino-3-(2-hydrazonopyridyl)-butane (LH) with copper(II) perchlorate hexahydrate and copper(II) nitrate trihydrate in 1:1molar proportion in methanol give rise respectively to Cu2L2(ClO4)2 (1a) and Cu2L2(NO3)2 (1b) in substantial yields. The complexes have been characterized by C, H and N microanalyses, copper estimation, ESI-MS, FT-IR, UV–Vis spectra, molar electric conductivity and room temperature magnetic susceptibility measurements. The X-ray crystal structures of both 1a and 1b have been determined. The structures reveal that both the complexes are oximato bridged dinuclear Cu(II) assemblies. The electrochemical studies of 1a and 1b show Cu(II) to Cu(III) oxidation in methanol. The thermal behavior of the nitrate analog, 1b, has also been forwarded to delve into the structure. Bond-Valence Sum (BVS) method of analyses was also performed to assign the oxidation state for each copper center both in 1a and 1b.