Linear Chain Compounds Research Articles

Co(NCS)2 Chain Compound with Alternating 5- and 6-Fold Coordination: Influence of Metal Coordination on the Magnetic Properties.

The reaction of Co(NCS)2 with 3-bromopyridine leads to the formation of discrete complexes [Co(NCS)2(3-bromopyridine)4] (1), [Co(NCS)2(3-bromopyridine)2(H2O)2] (2), and [Co(NCS)2(3-bromopyridine)2(MeOH)2] (3) depending on the solvent. Thermogravimetric measurements on 2 and 3 show a transformation into [Co(NCS)2(3-bromopyridine)2]n (4), which upon further heating is converted to [{Co(NCS)2}2(3-bromopyridine)3]n (5), whereas 1 transforms directly into 5 upon heating. Compound 5 can also be obtained from solution, which is not possible for 4. In 4 and 5, the cobalt(II) cations are linked by pairs of μ-1,3-bridging thiocyanate anions into chains. In compound 4, all cobalt(II) cations are octahedrally coordinated (OC-6), as is usually observed in such compounds, whereas in 5, a previously unkown alternating 5- and 6-fold coordination is observed, leading to vacant octahedral (vOC-5) and octahedral (OC-6) environments, respectively. In contrast to 4, the chains in 5 are very efficiently packed and linked by π···π stacking of the pyridine rings and interchain Co···Br interactions, which is the basis for the formation of this unusual chain. The spin chains in 4 demonstrate ferromagnetic intrachain exchange and much weaker interchain interactions, as is usually observed for such linear chain compounds. In contrast, compound 5 shows almost single-ion-like magnetic susceptibility, but the magnetic ordering temperature deduced from specific heat measurements is twice as high as that in 4, which might originate from π···π stacking and Co···Br interactions between neighboring chains. More importantly, unlike all linear Co(NCS)2 chain compounds, a dominant antiferromagnetic exchange is observed for 5, which is explained by density functional theory calculations predicting an alternating ferro- and aniferromagnetic exchange within the chains. Theoretical calculations on the two different cobalt(II) ions present in 5 predict an easy-axis anisotropy that is much stronger for the octahedral cobalt(II) ion than for the one with the vacant octahedral coordination, with the magnetic axes of the two ions being canted by an angle of 84°. This almost orthogonal orientation of the easy axis of magnetization for the two cobalt(II) ions is the rationale for the observed non-Ising behavior of 5.

Tracking variations in the abundance and composition of dissolved organic matter in solar ponds of oilfield-produced brine

The quantity and quality of dissolved organic matter (DOM) in the brine of solar ponds influence the efficiency of mineral extraction and brine evaporation rates. Here we report a characterization study of DOM in solar ponds of oilfield-produced brines using different approaches. The results showed that the concentrations of dissolved organic carbon and total dissolved solids exhibited a 2–3 fold increase with exposure time in the ponds. Analyses with two-dimensional correlation spectroscopy of attenuated total reflectance Fourier transform infrared spectroscopy and proton nuclear magnetic resonance, indicated that the aromatic and carboxylic acid structures in the DOM, were more susceptible to degradation/transformation compared with aliphatics, while aliphatics exhibited a preferential decline with increasing exposure time in the solar ponds. The relative abundance of aliphatic compounds (including functionalized ones) gradually decreased by 17.1% (r = −0.94, P < 0.001), in the solar pond process, while the opposite was observed for carbohydrates, which increased by 88.7% (r = 0.93, P < 0.001). Pyrolysis–gas chromatography–mass spectrometry revealed that the DOM in oilfield-produced brine contained polymethylene chain, terpenoid-like, carbohydrate (or carbohydrate-like) and aromatic structures. Terpenoid-like compounds were depleted while isoprenoid and linear polymethylene chain compounds increased upon irradiation in solar ponds. Finally, the guidelines for removing DOM from brine, and their ecological impacts and consequences in the process of brine resource exploitation, were discussed.

Metal-insulator transition in quasi-one-dimensional HfTe3 in the few-chain limit

The quasi-one-dimensional linear chain compound HfTe3 is experimentally and theoretically explored in the few- to single-chain limit. Confining the material within the hollow core of carbon nanotubes allows isolation of the chains and prevents the rapid oxidation which plagues even bulk HfTe3. High-resolution transmission electron microscopy combined with density functional theory calculations reveals that, once the triple-chain limit is reached, the normally parallel chains spiral about each other, and simultaneously a short-wavelength trigonal anti-prismatic rocking distortion occurs that opens a significant energy gap. This results in a size-driven metal-insulator transition.

Synthesis, structure and luminescence properties of zinc and cadmium linear-chain compounds with anionic monoalkoxy-tetracyanopropenes bridged by 4,4′-bipyridines

The synthesis, characterization and 3D structure determination of Zinc and Cadmium compounds are reported, containing the non-chelating bidentate ligand 4,4′-bipyridine and the anions 1,1,3,3-tetracyano-2-propoxy-propenide (tcnopr) or 1,1,3,3-tetracyano-2-ethoxy-propenide (tcnoet). The structures consist of linear chains (1D) built from metal ions and 4,4′-bipyridine, where the octahedral coordination around the metals is completed by two trans anions tcnoet (or tcnopr), and two trans-oriented water molecules. Weak interchain interactions are present, based on hydrogen bonds between the water ligands (both hydrogens are involved) and two CN groups of two nearby other chains. Metal-ligand distances appear as uneventful. For the same anion, the Zn and Cd compounds are isomorphous. Possible decomposition of the compounds has been investigated in the temperature range 30–800 °C in a static air atmosphere. Thermal analysis studies (TG, DTG, DTA) show that the axial water ligands for all three compounds are gradually lost upon heating above 60 °C to about 170 °C. Luminescence properties, recorded as powders, are reported as well, and these appear as strong for the Cd compound I, when irradiated at 390 nm, extremely weak for the Cd compound II, when irradiated at wavelengths from 300–400 nm, and moderately weak for the Zn compound III when irradiated at 385 nm.

Rational design of multi-channel continuous electronic/ionic conductive networks for room temperature vanadium tetrasulfide-based all-solid-state lithium-sulfur batteries

All-solid-state lithium-sulfur batteries can completely overcome safety issues and fast capacity fading by substitution of organic liquid electrolytes and eliminating polysulfide shuttle. However, the insulating nature of sulfur and large volume change still inhibit all-solid-state lithium-sulfur batteries from achieving favorable electrochemical performances. In this work, linear-chain compound vanadium tetrasulfide (VS4) anchored reduced graphene oxide (rGO-VS4) nanocomposites are successfully synthesized via a simple one-pot hydrothermal method. Furthermore, 10%rGO-VS4@Li7P3S11 nanocomposites with multi-channel continuous electronic/ionic conductive network are prepared by a facile liquid-phase deposition reaction and further employed as an alternative material for sulfur cathode in all-solid-state lithium batteries. Typically, Li/75%Li2S-24%P2S5-1%P2O5/Li10GeP2S12/10%rGO-VS4@Li7P3S11 all-solid-state lithium-sulfur batteries deliver high reversible capacity of 611 mAh g−1 at 0.1 A g−1 after 100 cycles, corresponding to 853 mAh g−1 based on the mass of sulfur. Even after being cycled at 0.5 A g−1 between 1.5 and 3.0 V for 500 cycles, it still shows the discharge specific capacity of 333 mAh g−1 based on sulfur content with excellent cycling stability. The excellent rate capability and cycle performances can be ascribed to the multi-channel continuous electronic/ionic conductive networks and the improved structural stability. In addition, the electrochemical reaction kinetics and capacity contributions as well as reaction mechanisms of 10%rGO-VS4@Li7P3S11 in all-solid-state lithium batteries were revealed by ex-situ characterization techniques.

A zero fading sodium ion battery: High compatibility microspherical patronite in ether-based electrolyte

The state-of-the-art vanadium sulfide VS4, a linear-chain compound of disulfide anions [S2]2– with vanadium atoms, has proved to have high potential in the field of secondary batteries due to its unique properties. Possessing qualities of a remarkable theoretical capacity, high electrical conductivity, natural abundance, and environmental friendliness, VS4 is determined to be a significant candidate for new high-energy storage systems. However, the fundamental drawbacks of capacity-fading issues, such as structure collapse or active-material loss during repeated cycling, critically limit the practical applications of VS4. Overcoming those obstacles, the present work used a design strategy to develop a VS4 electrode with a unique secondary morphology and utilize it in combination with a specific choice of an ether-based electrolyte for sodium ion batteries. This pristine VS4 displayed exceptional rate performance with excellent and stable cycling ability. An important finding in this study is the presence of a highly protective solid electrolyte interphase layer along the surface of the primary particle, which limits the polysulfide dissolution and hence preserves the active material during the reaction with sodium, as observed using ex-situ potentio-electrochemical impedance spectroscopy examinations. The detailed complex redox process of VS4/Na was also elucidated by ex situ X-ray photoelectron spectroscopy.

Elastic anisotropy and thermal properties of extended linear chain compounds MV2Ga4 (M = Sc, Zr, Hf) from ab-initio calculations

MV2Ga4 (M = Sc, Zr, Hf) compounds belong to an emerging class of materials showing a unique combination of unusual superconducting behavior with extended linear chains in the crystal structure. In order to gain insights into its mechanical and thermal properties, we have performed first-principles electronic-structure calculations in the framework of the Density Functional Theory (DFT). From the calculated second-order elastic constants, we have systematically shown that the extended linear vanadium chain substructures indeed give rise to an anisotropic regime in the elastic and mechanical moduli. The high density of valence and conduction electrons along the linear vanadium chains leads to a directional dependence of the reciprocal linear compressibility, Young’s modulus and shear modulus. Poisson’s ratio for several elongation directions is also drastically affected by the presence of extended V chains. If the elongation is along the V chains, all compounds exhibit practically the same Poisson ratio in directions perpendicular to it, further highlighting the importance of the V chains to the mechanical properties. Moreover, based on our results, we have discussed the possible consequences of the elastic anisotropy on the superconducting properties of the compounds. Finally, using the Debye–Grüneisen approximation, our calculations of thermal properties show a good agreement with the available experimental low temperature heat capacity data above the superconducting critical temperature.

Degradation of organic pollutants in near-neutral pH solution by Fe-C micro-electrolysis system

The degradation of organic pollutants in the simulated and realistic wastewaters was investigated by Fe-C micro-electrolysis system. Effects of initial pH, Fe/C mass ratio, gas bubbling type (air or N2) and the type of anions on degradation and mineralization of Sunset Yellow (SY) were studied. The degradation and mineralization efficiencies of 500mg·L−1 SY were approximately 99.0% and 77.5% after 90min treatment, when the initial pH, Fe/C ratio and air bubbling flow rate were 6.0, 1:1 and 45L·h−1, respectively. Besides, the type of anions had a significant influence on the Fe-C micro-electrolysis process. The results of kinetics study indicated that Fe-C micro-electrolysis process followed second-order-kinetics well. The degradation pathway and mechanism for SY were proposed based on FTIR and LC–MS analyses of treated wastewater. Additionally, the Fe-C micro-electrolysis process could dispose linear alkyl chain and benzene ring compounds efficiently under the optimal conditions, and the mineralization efficiencies were in the range of 94–96% and approximately 80%, respectively. The degradation feasibility of a realistic wastewater by the Fe-C micro-electrolysis system was investigated with landfill leachate. In conclusion, Fe-C micro-electrolysis system is an effective and promising technology for organic wastewater treatment in near-neutral pH condition.

Aroma Profile of Galangal Composed of Cinnamic Acid Derivatives and Their Structure-Odor Relationships

Cinnamic acid derivatives are important odorants due to their characteristic scent. Some fragrance materials, such as cinnamon bark, matsutake mushrooms, and Kaempferia galanga L. rhizome (galangal), contain several cinnamic acid derivatives as important odor constituents. The main odor constituent of glangal is (E)-ethyl 4-methoxycinnamate, but the odor of this compound is different from that of galangal. We investigated the aroma profile of galangal using our previously described method that considers the intermolecular interactions of the odorant compounds with their receptors. Odorant compounds in galangal were extracted by hexane extraction, steam distillation, and headspace sampling. The odor of the hexane extract was different from that of the steam - distillate and similar to that of galangal; therefore, we searched for the key compounds contributing to the aroma profile of galangal by separating the constituents of the hexane extract. A fraction with a galangal-like odor was obtained by bulb-to-bulb distillation of the hexane extract. The main component of this fraction was not (E)-ethyl 4-methoxycinnamate, but rather ethyl cinnamate. These results indicate that ethyl cinnamate is more important in the aroma profile of galangal than (E)-ethyl 4-methoxycinnamate. GC-MS analysis revealed that this fraction contained aromatic compounds, cyclic terpenes, and linear chain compounds in addition to ethyl cinnamate. We synthesized cinnamic acid derivatives and examined the importance of the odor expression of these cinnamic acid derivatives. Cinnamic acid derivatives lacking a p-methoxy group had a strong fruity odor. Replacement of the hydrogen atom at the para position with a methoxy group altered and weakened the odor. We found that a p-methoxy group in cinnamic acid derivatives plays an important role in the aroma profile of galangal.

Isolation and characterization of plant synergistic bacteria capable of degrading xenobiotics from oil spillage sites.

Oil spillage sites primarily contain various types of hydrocarbons, such as linear chain, polycyclic, and aromatic compounds, posing several detrimental effects on plants. Results from our previous study showed an alteration of various metabolomic parameters, indirectly resulting in an observable decline of growth in the mung seedlings upon incubation with phenol, toluene, xylene, and hexane. This study evaluates the role of these compounds upon plant growth and focusses to mitigate the effect of the same, using some isolated plant synergistic bacteria. We isolated Proteus sp., Streptococcus sp., and Enterococcus sp., and tested the synergism of them in mung seedlings (Vigna radiata) by hydroponics. Treatment with the above-mentioned compounds significantly reduced the root and shoot length of the seedlings when compared to the control. The bacterial treatment helped in reducing the adversity due to the xenobiotic insult, by improving the root shoot length of the treated seedlings. Proteus sp. was found to be the most promising among other isolates. In another experiment, plasmid profiling of the bacterial isolates was done, yielding a band of 4.5 kb common for all, serving as a clue to be the most probable plasmid responsible for the degradation of the compounds. Results from this study clearly indicate that Proteus sp. can be explored further for its plant synergism and xenobiotic degradative capability to exploit its potential in oil spillage land reclamation and establishing vegetation.

Synthesis, crystal growth, structural and magnetic characterization of NH4MCl2(HCOO), M=(Fe, Co, Ni)

An ambient-pressure solution route and an improved solvothermal synthetic method have been developed to produce polycrystalline powders and large single crystals of NH4MCl2(HCOO) (M=Fe, Co, Ni). The magnetic structure of the 1D linear chain compound NH4FeCl2(HCOO) has been determined by low-temperature neutron powder diffraction, revealing ferromagnetic intra-chain interactions and antiferromagnetic inter-chain interactions. The newly-reported Co and Ni analogs are isostructural with NH4FeCl2(HCOO), but there are significant differences in the magnetic properties of each compound; the Ni analog behaves similarly to the Fe compound but with stronger magnetic coupling, exhibiting antiferromagnetic ordering (TN=8.5K) and a broad metamagnetic transition between 2 and 5T, while the Co analog does not order magnetically above 2K, despite strong antiferromagnetic nearest-neighbor interactions.

Influence of Lewis acid charge and proximity in Mo[qbnd6]Mo⋯M linear chain compounds with M = Na+, Ca2+, Sr2+, and Y3+

The syntheses, X-ray structural characterizations, and electrochemical properties of four new paddlewheel [MMo2(SNO5)4Cl](n−1)+ (Mn+=Na+, Ca2+, Sr2+, Y3+; HSNO5=monothiosuccinimide) compounds are described here. By changing the Mn+ cation charge and size, we demonstrate a method for easily tuning the Lewis acidity of the MoMo quadruple bond and the [Mo2]4+/5+ redox potential. As the charge of the Mn+ cation is increased, the distal Mo atom becomes more Lewis acidic, leading to a shorter Mo2–Cl bond distance, and the [Mo2]4+/5+ redox couple becomes less accessible. As the Mn+⋯Mo2 distance is increased, the distal Mo atom becomes less Lewis acidic, leading to a longer Mo2–Cl bond distance.

Multiple Redox Modes in the Reversible Lithiation of High-Capacity, Peierls-Distorted Vanadium Sulfide.

Vanadium sulfide VS4 in the patronite mineral structure is a linear chain compound comprising vanadium atoms coordinated by disulfide anions [S2](2-). (51)V NMR shows that the material, despite having V formally in the d(1) configuration, is diamagnetic, suggesting potential dimerization through metal-metal bonding associated with a Peierls distortion of the linear chains. This is supported by density functional calculations, and is also consistent with the observed alternation in V-V distances of 2.8 and 3.2 Å along the chains. Partial lithiation results in reduction of the disulfide ions to sulfide S(2-), via an internal redox process whereby an electron from V(4+) is transferred to [S2](2-) resulting in oxidation of V(4+) to V(5+) and reduction of the [S2](2-) to S(2-) to form Li3VS4 containing tetrahedral [VS4](3-) anions. On further lithiation this is followed by reduction of the V(5+) in Li3VS4 to form Li3+xVS4 (x = 0.5-1), a mixed valent V(4+)/V(5+) compound. Eventually reduction to Li2S plus elemental V occurs. Despite the complex redox processes involving both the cation and the anion occurring in this material, the system is found to be partially reversible between 0 and 3 V. The unusual redox processes in this system are elucidated using a suite of short-range characterization tools including (51)V nuclear magnetic resonance spectroscopy (NMR), S K-edge X-ray absorption near edge spectroscopy (XANES), and pair distribution function (PDF) analysis of X-ray data.

Supported cobalt oxide nanoparticles as efficient catalyst in esterification and amidation reactions

Co/SBA-15 nanoparticle catalysts (CoNP) were prepared using a commonly adapted synthetic route and then utilised for esterification and amidation reactions using aromatic and linear chain compounds for the production of long chain esters and amides. The study shows that the use of CoNP catalysts favours the use of aromatic reactants with electron donating substituents specifically in the para position. For the amidation reaction, good to excellent yields were obtained demonstrating tolerance towards differently substituted aromatic compounds. Overall, the synthesized catalysts proved to be efficient and highly versatile, and recyclable under the investigated conditions.

A structural study of a three-membered linear metal chain compound at elevated pressure

Single crystal X-ray diffraction studies of the symmetrical molecular wire compound Co3(dpa)4Cl2·(dcm) have been performed up to a pressure of 3.6 GPa using both synchrotron and conventional sources. It is found that the terminal Co-Cl bond distance initially increases by 0.013(4) Å at 0.32 GPa after which it continuously decreases. Extensive theoretical calculations show that population of a thermally excited state containing increased Co-Cl anti-bonding character is a possibility at 0.32 GPa. The relative occupancy of the disordered dcm solvent molecule changes significantly with pressure and this is explained by the analysis of void spaces and Hirshfeld surfaces at different pressures. At 3.2 GPa, fingerprint plots derived from Hirshfeld surfaces indicate that neighbouring metal chain compounds approach each other such that short H···H interactions appear.

Lanthanide–radical linear chain compounds based on 2,4,4,5,5-pentamethylimidazoline-1-oxyl-3-oxide: Structure and magnetic properties

Two one-dimensional nitronyl nitroxide–lanthanide complexes [Ln(hfac)3(NITMe)]n (Ln(III)=Y (1), Dy(2), hfac=hexafluoroacetylacetonate; NITMe=2,4,4,5,5-pentamethylimidazolyl-1-oxyl-3-oxide) have been successfully prepared and characterized. Single crystal X-ray crystallographic analysis reveals that complexes 1 and 2 show similar linear chain structures composed of Ln(hfac)3 units bridged by NITMe radicals through their NO groups. Variable-temperature magnetic susceptibilities of Y complex show that there exists weak antiferromagnetic coupling between the radical ligands through the diamagnetic Y(III) ions. Alternating current (ac) susceptibilities of Dy complex reveal frequency dependent out-of-phase signals, indicating that it behaves as single-chain magnet.

Syntheses and Magnetic Properties Study of Isostructural BiM2BP2O10 (M = Co, Ni) Containing a Quasi-1D Linear Chain Structure

We present here the structures and magnetism of two quasi-1D linear chain compounds of BiM(2)BP(2)O(10) (M = Co, Ni), which were synthesized by traditional solid-state reactions for the first time. Two title compounds crystallize in the monoclinic system with space group P2(1)/c and feature novel 3D structures with a linear chain structure of {MO(6)}(n) further connected by [BP(2)O(10)](7-) anionic groups. The results of magnetic property measurements evidence the antiferromagnetic properties of both compounds in low magnetic field and a field-dependent metamagnetic transition from the antiferromagnetic to ferromagnetic ground state of the BiCo(2)BP(2)O(10) complex.

Linear chain and mononuclear tri-spin compounds based on the lanthanide-nitronyl nitroxide radicals: structural design and magnetic properties

Four Ln(III) complexes based on two nitronyl nitroxide radicals with different steric hindrance have been synthesized, characterized structurally and magnetically: [Ln(hfac)3(NITPhOEt)]n (Ce (1), Pr (2); hfac = hexafluoroacetylacetonate; and NITPhOEt = 4′-ethoxyphenyl-4,4,5,5-tetramethylimidazoline-1-oxyl-3-oxide); [Ln(hfac)3(NITPhOCH2Ph)2] (Ce (3), Pr (4); NITPhOCH2Ph = 4′-benzyloxyphenyl-4,4,5,5-tetramethylimidazoline-1-oxyl-3-oxide). The X-ray crystal structure analyses show that small steric hindrance of the radical makes complexes 1 and 2 show similar linear chain structures composed of Ln(hfac)3 units bridged by NITPhOEt radicals through their N–O groups. While the larger steric hindrance of the radical induces complexes 3 and 4 to be mononuclear tri-spin compounds, in which central Ln(III) ions are coordinated by three hfac and two NITPhOCH2Ph radicals. The variable-temperature magnetic susceptibility studies reveal that there are antiferromagnetic interactions between the paramagenetic ions (Ln(III) and radical) in all four complexes.

Catalytic Fast Pyrolysis of Cellulose with HZSM-5

An analytical pyrolyzer coupled with Gas Chromatography and Mass Spectrometry (Py-GC/MS) was employed to study the influence of HZSM-5 on the pyrolysis products of cellulose. The results revealed that pyrolysis products of cellulose consisted of light molecular weight products with linear chain, anhydrosugars and furan compounds. Light molecular products were mainly acetaldehyde and 2-propanone, 1-hydroxy; anhydrosugars were mainly levoglucosan (LG), levoglucosenone (LGO) and 1,4:3,6-Dianhydro-α-d-glucopyranose (DGP); Furans were mainly furfural (FF) and 5-(hydroxymethyl) furfural (HMF). The addition of HZSM-5 changed the contents of main products from fast pyrolysis of cellulose, especially for aromatic hydrocarbons, which belonged to light molecular products and increased rapidly. In addition, plenty of carbon dioxide appeared. With the addition of HZSM-5, the dehydration of LG was enhanced to produce LGO and then LGO was further decomposed into small molecular products with HZSM-5: cellulose ratio increasing. And the formation of FF and HMF were both inhibited with the addition of HZSM-5, but the formation of furan was improved. It was inferred that the addition of HZSM-5 could effectively promote the further dehydration of initial products from cellulose fast pyrolysis by the breakage of side chain.

Prorocentrol, a Polyoxy Linear Carbon Chain Compound Isolated from the Toxic Dinoflagellate Prorocentrum hoffmannianum

A polyoxy linear carbon chain compound, prorocentrol (1), was isolated from cultured cells of the dinoflagellate Prorocentrum hoffmannianum, which produces a polyether carboxylic acid, okadaic acid. The structure of 1 was elucidated by detailed analyses of 2D NMR spectra. Compound 1 possesses 30 hydroxy groups, 1 ketone, and 8 double bonds on the C65-linear carbon chain. Its partial relative configuration was deduced by the proton-proton and long-range carbon-proton coupling constants, and compound 1 showed moderate cytotoxicity and antidiatom activity.