Metal-sulfur Interactions Research Articles

Research progress on adsorption and separation of carbonyl sulfide in blast furnace gas.

The iron and steel industry is one of the foundational industries in China. However, with the introduction of energy-saving and emission reduction policies, desulfurization of blast furnace gas (BFG) is also necessary for further sulfur control in the iron and steel industry. Carbonyl sulfide (COS) has become a significant and difficult issue in the BFG treatment due to its unique physical and chemical properties. The sources of COS in BFG are reviewed, and the commonly used removal methods for COS are summarized, including the types of adsorbents commonly used in adsorption methods and the adsorption mechanism of COS. The adsorption method is simple in operation, economical, and rich in types of adsorbents and has become a major focus of current research. At the same time, commonly used adsorbent materials such as activated carbon, molecular sieves, metal-organic frameworks (MOFs), and layered hydroxide adsorbents (LDHs) are introduced. The three mechanisms of adsorption including π-complexation, acid-base interaction, and metal-sulfur interaction provide useful information for the subsequent development of BFG desulfurization technology.

Highly efficient and simultaneous magnetic solid phase extraction of heavy metal ions from water samples with l-Cysteine modified magnetic polyamidoamine dendrimers prior to high performance liquid chromatography

Due to the strong metal-sulfur interaction between mercapto groups and metal ions, which can be used to functionalize polyamidoamine dendrimer decorated Fe3O4 nanoparticles for high enrichment of trace heavy metal ions from waters. Based on this concept, polyamidoamine dendrimer modified Fe3O4 nanomaterials were functionalized with l-Cysteine and a new magnetic solid phase extraction for rapid adsorption and separation of Hg2+, Pb2+, Co2+ and Cd2+ from waters was established. The factors affecting extraction efficiency have been optimized. Upon the optimal parameters, the established method provided good linear ranges of 0.1–200 μg L−1 for Hg2+ and 0.05–200 μg L−1 for Pb2+, Co2+ and Cd2+, and high sensitivity with limits of detection (LOD) of 0.018 μg L−1, 0.014 μg L−1, 0.013 μg L−1 and 0.025 μg L−1 for Cd2+, Pb2+, Co2+ and Hg2+, respectively. Real water samples were utilized to validate the proposed method, and achieved results revealed that the proposed method was sensitive, effective, stable and suitable for monitoring Pb2+, Cd2+, Co2+and Hg2+ in environmental waters. This work provided a novel strategy for the simultaneous analysis of target cations in waters, and a new direction for developing decoration method of nanomaterials according to specific purpose.

Molecular geometries of transition metal complexes influenced by metal–sulfur interactions

Molecular geometries of transition metal complexes influenced by metal–sulfur interactions

Reactivity between late first-row transition metal halides and the ligand bis(2-pyridylmethyl)disulfide: Vibrantly-colored compounds with variable molecular geometries influenced by metal-sulfur interactions

The reactivity between late first-row transition metal halides and the disulfide-containing ligand bis(2-pyridylmethyl)disulfide was examined. From this survey, a series of mononuclear, four- and five-coordinate metal compounds were prepared and characterized. Single-crystal X-ray diffraction was employed to analyze the molecular structures in the solid state. The four-coordinate, tetrahedral compounds adopt either the form MLX2 (M = Zn; L = bis(2-pyridylmethyl)disulfide; X = Cl, Br) where the disulfide ligand is coordinated in a bidentate fashion by two nitrogen donors, or MLX (M = Cu; L = bis(2-pyridylmethyl)disulfide; X = Cl, Br) where the ligand is tridentate, coordinating via one sulfur and two nitrogen donors. The five-coordinate metal compounds, though varying significantly with regard to molecular geometry due to metal-sulfur interaction strength, adopt the form MLX2 (M = Zn, Cu, Co; L = bis(2-pyridylmethyl)disulfide; X = Cl, Br) with the ligand serving as a tridentate scaffold employing one sulfur and two nitrogen donors. The crystal structures ZnLCl2•CHCl3 and ZnLBr2•CHCl3 are isomorphous as are the structures ZnLCl2•CH2Cl2, ZnLBr2•CH2Cl2, and CoLBr2•CH2Cl2. The crystal structure of CoLCl2 is a kryptoracemate, having an enantiomeric pair within the asymmetric unit. Although chemically-identical, both hands of CoLCl2 have strikingly different Co–S distances: 2.599(2) versus 2.755(2) Å. Based on the X-ray crystal structures, the choice of halide does not appear to significantly influence the molecular geometry. For the solvated crystal structures, the identity of the solvent molecule has a drastic effect on the metal-sulfur distances. Compounds that contain metal-sulfur coordination do not appreciably affect the disulfide bond, as determined by X-ray crystallography and Raman spectroscopy. In addition to the standard analytical methods, variable-temperature NMR and UV–vis–NIR spectroscopy was utilized to gain insight into the solution behavior of the vibrantly-colored compounds.

Beneficial incorporation of metal-sulfur interaction in adsorption capacity of boron nitride based adsorbents used in highly selective sulfur removal

A series of novel nickel, molybdenum and cobalt loaded boron nitride adsorbents was synthesized and applied in adsorptive removal of DBT from model diesel fuel. These as-synthesized nano-composites were characterized by characterization techniques including scanning electron microscopy (SEM), X-ray diffraction (XRD), N2 adsorption–desorption, energy dispersive X-ray spectroscopy (EDX), Fourier transform infrared spectroscopy (FT-IR). Preliminary adsorption experiments were accomplished by utilizing 0.05 g adsorbent dosage, 3 h contact time at ambient temperature and pressure. An overall DBT removal performance order of: BN < Mo/BN < Co/BN < MoCo/BN < NiCo/BN was observed. Remarkable adsorption and selectivity of adsorbents could be related to S-M interactions and the π-complexation between metal oxides and adsorbate. BN loaded with cobalt and Ni (CoNi/BN) depicted best adsorptive desulfurization capacity of 33.2 mg DBT/g ads. The Langmuir isotherm was best fitted with the experiments. Kinetic investigations demonstrated the closest match with the pseudo-second-order kinetic. Selectivity of CoNi/BN in comparison with BN was increased from 14.4 to 27.6.mgDBt. g−1 adsorbent in the presence of naphthalene.

Manipulating metal–sulfur interactions for achieving high‐performance S cathodes for room temperature Li/Na–sulfur batteries

AbstractRechargeable lithium/sodium–sulfur batteries working at room temperature (RT‐Li/S, RT‐Na/S) appear to be a promising energy storage system in terms of high theoretical energy density, low cost, and abundant resources in nature. They are, thus, considered as highly attractive candidates for future application in energy storage devices. Nevertheless, the solubility of sulfur species, sluggish kinetics of lithium/sodium sulfide compounds, and high reactivity of metallic anodes render these cells unstable. As a consequence, metal–sulfur batteries present low reversible capacity and quick capacity loss, which hinder their practical application. Investigations to address these issues regarding S cathodes are critical to the increase of their performance and our fundamental understanding of RT‐Li/S and RT‐Na/S battery systems. Metal–sulfur interactions, recently, have attracted considerable attention, and there have been new insights on pathways to high‐performance RT‐Li/Na sulfur batteries, due to the following factors: (1) deliberate construction of metal–sulfur interactions can enable a leap in capacity; (2) metal–sulfur interactions can confine S species, as well as sodium sulfide compounds, to stop shuttle effects; (3) traces of metal species can help to encapsulate a high loading mass of sulfur with high‐cost efficiency; and (4) metal components make electrodes more conductive. In this review, we highlight the latest progress in sulfide immobilization via constructing metal bonding between various metals and S cathodes. Also, we summarize the storage mechanisms of Li/Na as well as the metal–sulfur interaction mechanisms. Furthermore, the current challenges and future remedies in terms of intact confinement and optimization of the electrochemical performance of RT‐Li/Na sulfur systems are discussed in this review.

High-Performance Lithium-Sulfur Batteries with Metal-Deposited Graphite Cathode and Lithium Polysulfide Catholyte

Lithium-sulfur (Li-S) batteries have attracted remarkable attention as next-generation batteries due to their low cost and high theoretical specific energy density.[1] However, it has encountered several difficulties, including low specific capacity due to the insulating nature of sulfur as well as poor cycle performance, which is caused by the dissolution of reaction intermediates (lithium polysulfide, LiPS) into the electrolyte. [2] Most strategies to overcome the above disadvantages are focused on designing carbon-based host materials, such as highly conductive and/or mesoporous carbon. [3] [4] However, it is difficult to completely suppress the dissolution of LiPS by the physical adsorption. Recent research thus focused on the utilization of chemical interactions between LiPS and electrode additive, mainly metal particles, to suppress the dissolution of LiPS. [5] Although it has been reported that the addition of metal improves the capacity retention and suppresses the self-discharge, the mechanistic understanding is still lacking.In this study, we selected Au and Ag as a metal additive, which has similar electrical conductivity but different affinity towards sulfur, to clarify the effect of metal-sulfur interaction on battery performances. We selected catholyte, in which LiPS (Li2S8) was previously dissolved, was selected as an electrolyte to achieve a continuous supply of LiPS to the positive electrode. Galvanostatic charge-discharge measurements revealed that the charge/discharge capacity affected by the metal addition; 75.8 mAh cm-3 (G) < 77.4 mAh cm-3 (Ag/G) < 99.5 mAh cm-3 (Au/G), with excellent initial discharge capacity for Au-decorated electrode. Furthermore, we confirmed the effect of the amount of metal additive on the charge/discharge capacity. The result thus indicates (1) addition of metal with a strong affinity towards sulfur and (2) optimization of its amount is crucial to improve Li-S battery performances. The improvement in capacity retention rate was confirmed for the metal-decorated electrode; capacity retention at the 20th cycle was G = 68.1 % < Ag = 89.3 % < Au = 94.9 %. The interaction between the metal additives and LiPS may contribute to anchor LiPS at the vicinity of the electrode, leading the improvement in the cyclability.The reason for the improvement in the cyclability will be discussed based on the surface product analysis of the electrode after initial charge and discharge, as deduced from on-line gas chromatography-mass spectrometry (GC-MS) measurements. We will also discuss the effect of metal additives on the reaction mechanism of sulfur redox reaction by in situ probing of the reaction intermediates using infrared spectroscopy. Elucidation of the reaction mechanism opens up the new avenue to optimize both electrode and electrolyte materials, which can further improve the performance of the Li-S battery technology.[1] Richard, V. N, Nature, 2014, 507, 26-28.[2] Hailiang, W. et al. Nano Lett. 2011, 11, 2644-2647.[3] Kunpeng, C. et al. Nano Lett. 2012, 12, 6474-6479.[4] Jorg, S. et al. Angew. Chem. Ed. 2012, 51, 3591-3595.[5] Chao-Ying, F. et al. ACS Appl. Mater. Interfaces, 2015, 7, 27959-27967.

Elucidation of Active Sites on S, N Codoped Carbon Cubes Embedding Co–Fe Carbides toward Reversible Oxygen Conversion in High‐Performance Zinc–Air Batteries

The development of high-performance but low-cost catalysts for the electrochemical oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) is of central importance for realizing the prevailing application of metal-air batteries. Herein a facile route is devised to synthesize S, N codoped carbon cubes embedding Co-Fe carbides by pyrolyzing the Co-Fe Prussian blue analogues (PBA) coated with methionine. Via the strong metal-sulfur interaction, the methionine coating provides a robust sheath to restrain the cubic morphology of PBA upon pyrolysis, which is proved highly beneficial for promoting the specific surface area and active sites exposure, leading to remarkable bifunctionality of ORR and OER comparable to the benchmarks of Pt/C and RuO2 . Further elaborative investigations on the activity origin and postelectrolytic composition unravel that for ORR the high activity is mainly contributed by the S, N codoped carbon shell with the inactive carbide phase converting into carbonate hydroxides. For OER, the embedded Co-Fe carbides transform in situ into layered (hydr)oxides, serving as the actual active sites for promoting water oxidation. Zn-air batteries employing the developed hollow structure as the air cathode catalyst demonstrate superb rechargeability, energy efficiency, as well as portability.

Synthesis of carbon-supported sub-2 nanometer bimetallic catalysts by strong metal-sulfur interaction.

Small-sized bimetallic nanoparticles that integrate the advantages of efficient exposure of the active metal surface and optimal geometric/electronic effects are of immense interest in the field of catalysis, yet there are few universal strategies for synthesizing such unique structures. Here, we report a novel method to synthesize sub-2 nm bimetallic nanoparticles (Pt–Co, Rh–Co, and Ir–Co) on mesoporous sulfur-doped carbon (S–C) supports. The approach is based on the strong chemical interaction between metals and sulfur atoms that are doped in the carbon matrix, which suppresses the metal aggregation at high temperature and thus ensures the formation of small-sized and well alloyed bimetallic nanoparticles. We also demonstrate the enhanced catalytic performance of the small-sized bimetallic Pt–Co nanoparticle catalysts for the selective hydrogenation of nitroarenes.

Experimentally Validated Structures of Supported Metal Nanoclusters on MoS2.

In nanometer clusters (NCs), each atom counts. It is the specific arrangement of these atoms that determines the unique size-dependent functionalities of the NCs and hence their applications. Here, we employ a self-consistent, combined theoretical and experimental approach to determine atom-by-atom the structures of supported Pt NCs on MoS2. The atomic structures are predicted using a genetic algorithm utilizing atomistic force fields and density functional theory, which are then validated using aberration-corrected scanning transmission electron microscopy. We find that relatively small clusters grow with (111) orientation such that Pt[11̅0] is parallel to MoS2[100], which is different from predictions based on lattice-match for thin-film epitaxy. Other 4d and 5d transition metals show similar behavior. The underpinning of this growth mode is the tendency of the NCs to maximize the metal-sulfur interactions rather than to minimize lattice strain.

SERS detection and DFT calculation of 2-naphthalene thiol adsorbed on Ag and Au probes

Two different surface enhanced Raman scattering (SERS) sensors are described, tested and compared against the detection of 2-naphthalenethiol (2NPT, a volatile compound) in both solution state as well as vapor phase. The first sensor is based on an optical fiber properly modeled to induce the adhesion of colloidal Ag nanoparticles on its surface. Excitation and detection of the Raman signal is performed through the optical fiber that can be used as in situ probe for the detection of molecules adsorbed on the SERS sensitized surface. The second SERS sensor is based on nanostructured substrates consisting of Au nanoparticles produced by pulsed laser deposition in presence of a controlled Ar atmosphere. Details at the nanometer scale were observed by SEM and TEM imaging to understand the size and structure of the islands formed as a function of deposition parameters that were selected in order to maximize their SERS response. The sensitivity of the substrates to volatile species was tested by letting evaporate controlled drops of a methanol solution of 2NPT in a chamber of known volume, where the substrate was placed. After complete evaporation of the drops, this provided an in-situ environment suitable for vapor phase measurements at known concentration. SERS spectra were collected after exposing the substrates to the environment within the chamber (vapor phase measurements) or dipping them in a solution for condensed state measurements. The complete absence of the SH stretching peak in the SERS spectra proves the covalent bonding of 2NPT to the metal substrates via the sulfur atom. DFT calculations, including metal-sulfur interaction, provide a good description of the observed SERS spectra. The reported data allow concluding that our SERS substrates are suitable for detection of volatile compounds.

Synthesis of a novel poly-thiolated magnetic nano-platform for heavy metal adsorption. Role of thiol and carboxyl functions

We report a novel strategy for the synthesis of magnetic nano-platforms containing free thiol groups. It first involves the synthesis of a poly(acrylic acid) copolymer containing disulfide bridges between the linear chains through di-ester linkages, followed by the anchoring of this new ligand to magnetite nanoparticles using a ligand exchange reaction. Finally, free SH groups are obtained by treating the resulting disulfide-functionalized magnetic nano-system with tributyl phosphine as reducing agent. The characterization of the resulting 17nm nanoparticles (Fe3O4@PAA-HEDred) by FTIR and TGA confirms the attachment of the copolymer through iron carboxylates. XRD, TEM and magnetic measurements indicate an increase in the inorganic core diameter and the occurrence of strong magnetic inter-particle interactions during the exchange reaction, although coercitivity and remanence drop to near zero at room temperature. Afterwards, Fe3O4@PAA-HEDred nanoparticles were tested as sorbent for Pb2+ and Cd2+ cations in aqueous media. XPS measurements were performed in order to unravel the role of both carboxyl and thiol functions in the adsorption process. For the sake of comparison, the same study was performed using bare Fe3O4 nanoparticles and a nanosystem with disulfide groups (Fe3O4@DMSA). The joint analysis of the Pb 4f, Cd 3d, Fe 2p and S 2p high resolution spectra for the nanostructured materials indicates that metal-sulfur interactions are dominant if free SH groups are present, but if not, the main adsorption route entails metal-carboxyl interactions. Even in presence of unbound thiol moieties, carboxyl groups participate due to favoured steric availability.

Synthetic and structural studies of heteroleptic platinum(II) and palladium(II) complexes containing thiacrown and monodentate phosphane ligands

We wish to report the syntheses, spectroscopic, and structural properties for six new Pt(II) and Pd(II) heteroleptic complexes containing the monodentate phosphane ligands PTA (1,3,5-triaza-7-phosphaadamantane) or PMe3 (trimethylphosphane) and the crown trithioether [9]aneS3 (1,4,7-trithiacyclononane). All six reported complexes have the general formula [M([9]aneS3)(P2)](PF6)2 or [M([9]aneS3)(P)(Cl)](PF6) where M=Pt(II) or Pd(II) and P is the monodentate phosphane ligand. All six complexes form similar structures in which the metal center is surrounded by two sulfur atoms from the trithioether ligand and a cis arrangement of either the two phosphorus donors or the chlorido and phosphorus donor. The third sulfur from the [9]aneS3 interacts with the metal at a greater distance (2.711(2)Å–3.078(8)Å), resulting in elongated square pyramidal geometries. These axial distances are controlled by the donor abilities of the phosphane ligand with PTA and PMe3 serving as stronger donors. The two chlorido complexes show longer metal–sulfur interactions, consistent with the strong donor properties of the anionic chlorido ligand. Although the symmetrical bis complexes display typical 1H and 13C NMR behavior in the [9]aneS3 region, the less symmetrical chlorido complexes show a more complex pattern in their spectra. The 195Pt NMR chemical shifts are consistent with the presence of [S2P2+S1] or [S2PCl+S1] coordination environments.

Thiol Reactive Probes and Chemosensors

Thiols are important molecules in the environment and in biological processes. Cysteine (Cys), homocysteine (Hcy), glutathione (GSH) and hydrogen sulfide (H2S) play critical roles in a variety of physiological and pathological processes. The selective detection of thiols using reaction-based probes and sensors is very important in basic research and in disease diagnosis. This review focuses on the design of fluorescent and colorimetric probes and sensors for thiol detection. Thiol detection methods include probes and labeling agents based on nucleophilic addition and substitution, Michael addition, disulfide bond or Se-N bond cleavage, metal-sulfur interactions and more. Probes for H2S are based on nucleophilic cyclization, reduction and metal sulfide formation. Thiol probe and chemosensor design strategies and mechanism of action are discussed in this review.

Synthesis and characterization of nickel doped cadmium sulfide (CdS:Ni2+) nanoparticles

Nickel doped cadmium sulfide (CdS:Ni2+) nanocrystals were synthesized at three different pH values. Nanocrystalline state of nickel doped cadmium sulfide material was established using X-ray diffraction analysis. Peak broadening and peak shifts in the XRD spectra were caused by the replacement of Cd2+ with Ni2+. Particles size (∼62nm) and the morphology of the synthesized nanoparticles were established through SEM analysis. The TEM analysis further established the presence of nanostate with particles size of 35nm. The EDS analysis confirmed the existence of Ni in all the three samples. Blue shift in the absorption region and increase in the bandgap to the larger value (3.72eV) were attributed to the nano dimensional state and incorporation of dopant into the host lattice. Weak metal sulfur interaction was identified from the FT-IR spectroscopy. The room temperature magnetic studies showed that 10% nickel doped CdS at 10 pH, 11.0 pH and 9.0 pH showed weak ferromagnetic and strong ferromagnetic hysteresis. The variations in the magnetic property of the nanomaterials were caused by the weak interaction of Ni2+ with the host material.

π Delocalization in iridathiabenzenes

Fenske–Hall calculations were carried out for (PEt 3) 3Ir(C 7H 9) ( 1), [(PEt 3) 3Ir(C 6H 8S)] + ( 2), [(S- t-but)(PEt 3) 2]Ir(C 6H 8S) ( 3), and [(S- t-but)(PMet 3) 3]Ir(C 6H 8S) ( 4) in order to compare the degree of π delocalization in the metallathiacycle rings of ( 2) and ( 3). In comparison to ( 1), a true iridabenzene and ( 4), an iridathiacyclobutadiene, the π ring systems in ( 2) and ( 3) are considerably more localized than the π system in ( 1) but are not totally localized. Strong metal–sulfur bonding in ( 2) disrupts the π ring system and results in some localization of the ring π bonds. The introduction of the donor thiolate ligand in ( 3) disrupts the ring of π system even more by destabilizing the metal orbitals used for metal–sulfur interactions. This weakens the metal–sulfur interaction seen in ( 2) and leads to even more localization of the ring π system in ( 3).

Preparation and characterization of hybrid platinum/Prussian blue nanoparticles

Colloidal dispersions of hybrid nanoparticles composed of Prussian blue (PB) and platinum (Pt) were prepared by adding K 4FeCN 6 and K 2PtCl 6 in turn into PB colloid solution, in which Pt ion and [FeCN 6] 4− in an aqueous solution were reduced and oxidized separately. The formation of hybrid platinum/Prussian blue (Pt/PB) nanoparticles was characterized by UV–vis spectrophotometry and transmission electron microscopy (TEM). The diameter of obtained Pt/PB nanoparticles is about 20 nm. The characteristic absorbance peaks of PB nanoparticles at 720 nm could be observed from the Pt/PB colloid. However, the peak magnitude decreases compared with that of PB, which means that Pt covers partly PB nanoparticles. The self-assembled 1,3-propanedithiol was employed to anchor the metal-modified PB nanoparticles on Au electrodes by the strong metal–sulfur interactions. The study of electrochemical cyclic voltammetry shows that PB or Pt of Pt/PB is involved in electrochemical catalytically reduction of oxygen.

Decomposition of dimethyldisulfide on various W–Ni catalysts

The decomposition of dimethyldisulfide (DMDS) was studied on WNi/Al 2O 3, WNi/Beta + Y, WNi/Beta, and WNi/Y catalysts. DMDS was rapidly converted to methanethiol. The methanthiol was subsequently transformed to methane, H 2S, and dimethylsulfide (DMS). On WNi/Al 2O 3, methanthiol and dimethylsulfide were slowly consumed to sulfide catalyst. On the zeolite containing catalysts, the methanthiol and dimethylsulfide (DMS) were completely and rapidly consumed for sulfidation. Considerable amounts of C4–C5 alkanes were formed during the transformation of dimethylsulfide (DMS) on the zeolite containing catalysts. The formation of the alkanes was closely related to the synergic effect between the metal–sulfur interaction and the acidity of catalysts. The quantity of alkanes changed directly proportionally with the reaction pressure.

Homoleptic platinum(II) and palladium(II) complexes of 1,5,9-trithiacyclododecane: the crystal structures of [Pt(12S3) 2](PF 6) 2 · 2CH 3NO 2 and [Pd(12S3) 2](BF 4) 2 · 0.5H 2O

The synthesis, spectroscopy, electrochemistry, and crystal structures of two new mononuclear homoleptic Pt(II) and Pd(II) complexes with the crown trithioether 1,5,9-trithiacyclododecane (12S3) are reported. In contrast to behavior with analogous smaller ring trithiacrowns, both metal complexes exhibit exodentate axial sulfur donors, a consequence of the preferred conformation of the 12S3 ligand. The lack of two axial metal–sulfur interactions correlates with the observed electronic spectroscopy and oxidative electrochemistry displayed by the complexes and contrasts with properties exhibited by complexes containing smaller polythioether macrocycles. The two complexes have electronic spectra dominated by charge transfer, not d–d bands and show no M 2+/M 3+ couples. Both complexes show a fluxional 12S3 ligand in solution due to a 1,5-metallotropic shift, an uncommon observation of this particular type of intramolecular ligand exchange. The 195Pt NMR chemical shift of −4201 ppm for [Pt(12S3) 2] 2+ is consistent with an alternating positioning of the four sulfur lone pairs on the coordinated thioethers. Although 12S3 is poorly pre-organized for facial complexation, its flexibility to position a sulfur in an exodentate fashion enables it to form stable complexes with d 8 metal ions such as Pt(II) and Pd(II).

Unique structural topologies involving metal–metal and metal–sulfur interactions: salts of [Ni(C3S5)2]x− with cis-anti-cis-dicyclohexyl-18-crown-6 complexed counter ions

Preparation by electrocrystallisation has been carried out for the salts [Rb(anti-dchyl-18c6)]2[Ni(dmit)2] 1, [Rb(anti-dchyl-18c6)][Ni(dmit)2] 2, [Cs(anti-dchyl-18c6)]2[Ni(dmit)2] 3 and [Cs(anti-dchyl-18c6)1.5][Ni(dmit)2]64 (anti-dchyl-18c6 = cis-anti-cis-dicyclohexyl-18-crown-6, dmit = C3S5). Salts 1 and 3 involve the planar dianionic nickel complex sandwiched by two metal–crown units. This leads to short Rb+ ⋯ Ni and Rb+ ⋯ S interactions in 1 and the shortest recorded Cs+ ⋯ Ni distance of 3.47 A in 3, presumably stabilised by the four surrounding S atoms at 3.73–4.44 A. DFT calculations on the dianionic salts 1 and 3 indicate an essentially electrostatic interaction between the [Ni(dmit)2]2− complex and the Rb+ or Cs+ ion and show frontier orbitals qualitatively similar to those previously derived from EHMO calculations on molecular conductors containing [Ni(dmit)2]. Salt 2 consists of non-stacked nickel complexes arranged in chains linked by S ⋯ Rb+ interactions through the terminal sulfurs with the Rb+ ion placed exactly within the plane of the crown oxygens. Magnetic susceptibility measurement indicated weak antiferromagnetic interactions. Salt 4 shows a 2-D sheet of nickel complexes stacked in a herringbone arrangement separated by layers of counter ions complexed by the crowns in a disordered manner with the anion ∶ cation ratio of 6 ∶ 1 uniquely high among [Ni(dmit)2]x− salts. Salt 4 displays semiconductor behaviour with σRT = 10−2 S cm−1.