Anionic Chains Research Articles

Optical and photocatalytic properties of conjugated-organic-templates derived semiconducting iodocuprates hybrids

Abstract Two iodocuprates hybrids, [Me3TPB][Cu5I8] (1, Me3(TPB) = N,N′,N″-trimethyl-1,3,5-tris(4-pyridyl)benzene) and [Me3TIB]2[Cu15I21] (2, Me3(TIB) = N,N′,N″-trimethyl-1,3,5-tris(1-imidazolyl)benzene), directed by in-situ N-alkylation conjugated-organic-templates were solvothermally achieved. 1 features a one-dimensional (1-D) anionic chain built by {Cu5} clusters. 2 exhibits a 2-D layered network based on a rare {Cu15} cluster. 1 is expressed as the first case of halometallate based on TPB. Compared with raw material CuI, both of them possess narrower band gaps and show potential semiconductor properties, which lead to the efficient and stable photocatalytic behavior of 1 under visible-light irradiation. This work further demonstrates that the introduction of conjugated organic templates is beneficial to generating of semiconducting halometallates with narrow band gaps.

Crystallographic and theoretical interpretation of supramolecular architecture in a new salt hydrate of DL-Tartaric acid and Dimethylamine (DLTA-DA)

Herein, DL-tartaric acid normally used as a coformer in cocrystal engineering is exploited to create the hybrid molecule with secondary amine utilizing the supramolecular synthon approach. The crystal engineering tactics are potentially applied to a wide range of crystalline materials and the nature of the intermolecular interactions, hydrogen bonds in particular which decide the supramolecular stabilization of the solid form can be studied. The mechanochemical mixing of DL-tartaric acid and aqueous dimethylamine showed salt-pseudopolymorphism, resulted in N-methylmethanaminium-3-carboxy-2,3-dihydroxypropanoate hydrate. The interactions present between the molecules were demonstrated by simulating the FTIR spectrum which showed O − H stretching of the carboxylic group that did not match with experimental value as only one supramolecular unit was considered; whereas the experimental spectrum displayed a broad band for O − H stretch at 3200 cm−1. The salt crystallized in the monoclinic system with space group I2/a. The complementary hydrogen bond functionalities present in the molecules instilled the formation of O–H···O, O–H···N, and N − H···O intermolecular contacts. From the graph set analysis, it was noted that the supramolecular architecture was maintained by the homosynthon dimer and one-dimensional O–H···O anionic chain built by R22(12)and C(7) motifs. Additionally, the cage type assembly was formed by additional hydrogen bonds present in between the chains with H2O as a linker. The 2D fingerprint plots confirmed the maximum percentage contribution of -O–H (59%) towards the Hirshfeld surface. Hence, a full analysis of crystal packing and discussions in the context of the supramolecular chemistry of the salt hydrate is presented.

Neutral 1D Perovskite-Type ABX3 Ferroelectrics with High Mechanical Energy Harvesting Performance

Organic–inorganic ABX3 hybrids with perovskite structures have drawn enormous attention owing to their intriguing chemical variability, structural tunability, and diversity of application-worthy properties. Herein, we report the synthesis of a new neutral ABX3 hybrid ferroelectric compound [Me3NCH2CH2OH]CdCl3 (1), which exhibits a 1D chain structure of edge-sharing CdCl5O octahedra that are connected to cationic [Me3NCH2CH2OH]+ units via its peripheral OH functionality. The single-crystal X-ray diffraction analysis of the compound at 363 K reveals the conversion of 1 to its coordination isomer 1′, in which the anionic chain consists of face-sharing CdCl6 octahedra and the cations are uncoordinated. The piezoresponsive force microscopy analysis performed on a single crystal of 1 confirms the existence of polarizable domains in it. The ferroelectric P–E loop measurements on 1 show a high remnant polarization value of 17.1 μC cm–2. Composite devices based on 1 and polydimethylsiloxane (PDMS) prepared with varying wt % compositions are examined for mechanical energy harvesting applications. The highest open-circuit voltage of 55.2 V and a maximum power density of 70.9 μW cm–2 at an optimal load of 4 MΩ were obtained for the 15 wt % 1–PDMS device. The harvested energy is shown to be effective for capacitor charging and light-emitting diode (LED) flash lighting applications.

Spatial Variations of Low-mass Negative Ions in Titan’s Upper Atmosphere

Abstract Observations with Cassini’s Electron Spectrometer discovered negative ions in Titan’s ionosphere, at altitudes between 1400 and 950 km. Within the broad mass distribution extending up to several thousand amu, two distinct peaks were identified at 25.8–26.0 and 49.0–50.1 amu/q, corresponding to the carbon chain anions CN− and/or for the first peak and C3N− and/or C4H− for the second peak. In this study we present the spatial distribution of these low-mass negative ions from 28 Titan flybys with favorable observations between 2004 October 26 and 2012 May 22. We report a trend of lower densities on the night side and increased densities up to twice as high on the day side at small solar zenith angles. To further understand this trend, we compare the negative ion densities to the total electron density measured by Cassini’s Langmuir Probe. We find the low-mass negative ion density and the electron density to be proportional to each other on the day side but independent of each other on the night side. This indicates photochemical processes and is in agreement with the primary production route for the low-mass negative ions being initiated by dissociative reactions with suprathermal electron populations produced by photoionisation. We also find the ratio of to to be highly constrained on the day side, in agreement with this production channel, but notably displaying large variations on the night side.

Interstellar nitrile anions: Detection of C3N- and C5N- in TMC-1.

We report on the first detection of C3N- and C5N- towards the cold dark core TMC-1 in the Taurus region, using the Yebes 40 m telescope. The observed C3N/C3N- and C5N/C5N- abundance ratios are ~140 and ~2, respectively; that is similar to those found in the circumstellar envelope of the carbon-rich star IRC +10216. Although the formation mechanisms for the neutrals are different in interstellar (ion-neutral reactions) and circumstellar clouds (photodissociation and radical-neutral reactions), the similarity of the C3N/C3N- and C5N/C5N- abundance ratios strongly suggests a common chemical path for the formation of these anions in interstellar and circumstellar clouds. We discuss the role of radiative electronic attachment, reactions between N atoms and carbon chain anions C n -, and that of H- reactions with HC3N and HC5N as possible routes to form C n N-. The detection of C5N- in TMC-1 gives strong support for assigning to this anion the lines found in IRC +10216, as it excludes the possibility of a metal-bearing species, or a vibrationally excited state. New sets of rotational parameters have been derived from the observed frequencies in TMC-1 and IRC +10216 for C5N- and the neutral radical C5N.

Modulation of the Structure and Photoluminescence of Bismuth(III) Chloride Hybrids by Altering the Ionic-Liquid Cations.

Two bismuth(III) halides hybrids with room-temperature phosphorescence (RTP), namely, [BPy]2[Bi2Cl8(bpym)] (1, BPy = N-butylpyridinium) and [EPy]2[Bi2Cl8(bpym)] (2, EPy = N-ethylpyridinium), were synthesized and characterized. Structural comparison reveals that 1 and 2 possess similar anionic zigzaglike chain of [Bi2Cl8(bpym)]n2n-; however, different packing modes of anion/cations and thus different weak interactions. Interestingly, the utilization of pyridinium cations with different length of alkyl chain could tune the RTP behaviors efficiently. The RTP quantum yield (QY) is increased more than 5-fold from 1 to 2 probably due to more rigid structure of 2 arising from the additional H-bond and anion-π interactions, as confirmed by Hirshfeld surfaces analyses and PLATON calculations. Moreover, additional π-π interactions in 1 could stabilize the triplet excitons, leading to an average lifetime of 1 (11.36 ms at 77 K and 1.407 ms at 298 K) being higher than 2 (0.3618 ms at 77 K and 0.07511 ms at 298 K). Density functional theory (DFT) calculations confirm that inorganic moiety to organic ligand charge-transfer (IOCT) is involved in the phosphorescence process. The present work provides a new sight into the design of RTP metal halides through studying the structure-RTP relationship.

Hydrothermal syntheses, structures and properties of a series of new hybrid iodometallates containing rare cross-shaped spirobifluorene derivatives

A series of new hybrid iodometallates [H4Spiro-4-py]n[Cu7I10]n(I3−)n·0.5(I2)n·nH2O (1), [Cu2I2(Spiro-3-py)]n·0.75n(DMF)·0.25nH2O (2), [H2Spiro-4-py][H3Spiro-4-py][Ag10I20]0.5·H2O (3) and [H2Spiro-4-py]n[H3Spiro-4-py]n[Ag8I13]n·2.5H2O (4) were hydrothermal synthesized. 1 contains 1-D chain [Cu7I10]n based on new [Cu7I12] cluster, free I3− anions and I2 molecules, which are interconnected by weak I⋯I interactions to generate a novel polyiodide {[Cu7I10](I3−)·(I2)}n framework. 2 features a neutral sql layer [Cu2I2(Spiro-3-py)]n constructed by the interconnection of the {Cu2I2} dimers and Spiro-3-py ligands. The anionic [Ag10I20]10− framework of 3 can be described as an aggregation of two tetrameric [Ag4I8] clusters and one dimeric [Ag2I6] unit via sharing corner. The 1-D anionic chain [Ag8I135−]n of 4 is built up from the alternate connection of tetrameric [Ag4I8] units and rare larger [Ag12I20] clusters, which offers the only example of 1-D iodoargentates based on two types of iodoargentate clusters. The optical and photoelectronic properties of all compounds were also investigated.

Synthesis, X-ray powder diffraction study, thermal analysis, Hirshfeld surface analysis and optical properties of new crystalline polymer: {(C2H10N2)(MnCl(NCS)2)2}n

Synthesis, structural and optical properties are given for a new organic manganese pseudo halide material. The crystal structure has been solved by ab initio using direct methods from powder data and has been confirmed by additional single-crystal data collected with a CCD area detector. The structure of the {(C2H10N2)(MnCl(NCS)2)2}n reveals that the adjacent Mn(II) centres are bridged by a pair of SCN− anions to form a 1-D array giving rise to the anionic chains (MnCl(NCS)2)nn−. These chains are themselves interconnected by means of N–H•••Cl(S) hydrogen bonds originating from the organic cation [(NH3)2(CH2)2]2+. Optical parameters, such as extinction coefficient, refractive index, permittivity refractive, optical conductivity, electrical conductivity and electrical susceptibility were studied using the absorbance spectra UV-vis spectrophotometer in the spectral range 200-800 nm. Atomic Mulliken charges, energies of frontier molecular orbitals (EHOMO and ELUMO), energy band gap (EHOMO–ELUMO), chemical hardness (η), global electrophilicity index(ω) and Electronegativity (χ) were calculated by Density functional theory (DFT) using B3LYP method. The direct optical band gap energy deduced from the UV–VIS spectroscopy is Eg= 3.61 eV.

Difluorocarbene Generation from TMSCF3: Kinetics and Mechanism of NaI-Mediated and Si-Induced Anionic Chain Reactions.

The mechanism of CF2 transfer from TMSCF3 (1), mediated by TBAT (2-12 mol %) or by NaI (5-20 mol %), has been investigated by in situ/stopped-flow 19F NMR spectroscopic analysis of the kinetics of alkene difluorocyclopropanation and competing TFE/c-C3F6/homologous perfluoroanion generation, 13C/2H KIEs, LFERs, CF2 transfer efficiency and selectivity, the effect of inhibitors, and density functional theory (DFT) calculations. The reactions evolve with profoundly different kinetics, undergoing autoinhibition (TBAT) or quasi-stochastic autoacceleration (NaI) and cogenerating perfluoroalkene side products. An overarching mechanism involving direct and indirect fluoride transfer from a CF3 anionoid to TMSCF3 (1) has been elucidated. It allows rationalization of why the NaI-mediated process is more effective for less-reactive alkenes and alkynes, why a large excess of TMSCF3 (1) is required in all cases, and why slow-addition protocols can be of benefit. Issues relating to exothermicity, toxicity, and scale-up are also noted.

Effect of ionic liquids’ chemistry on their lubrication behaviour under various contact pressures

The promising properties of Ionic Liquids (ILs) such as their low vapour pressure, high thermal stability and high thermal conductivity make them strong candidates to be used as either neat lubricants or additives. The effect of ionic liquids' chemistry on their lubrication behaviour is examined in this study by comparing the performance of five neat ILs, i.e. Ethyl Methyl Imidazolium Ethyl Sulfate (EMIM ESU), Ethyl Methyl Imidazolium Octyl Sulfate (EMIM OSU), Butyl Methyl Imidazolium Octyl Sulfate (BMIM OSU), Ethyl Methyl Imidazolium Ethyl Phosphate (EMIM EP) and Butyl Methyl Phosphonium Methyl Sulfate (PSU). The first three are used to reveal the effects of both anion and cation chain length, while the other two are used to reveal the effect of anion and cation types. Tribological experiments are performed using a nanotribometer with a borosilicate ball rubbing against a silicon plate. 3D optical microscopy and X-ray Photoelectron Spectroscopy (XPS) are used to examine surface morphology and surface chemistry, respectively. The results showed that all parameters related to ILs’ chemistry have a strong influence on the tribological behaviour of the lubricated surfaces. The increase of anion/cation chain length leads to a significant decrease in wear and friction coefficients. The influence of anion and cation types appeared to vary depending on the contact pressure.

Hybrid Sequences that Express both Aromatic Amide and α-Peptidic Folding Features.

Foldamers combining aliphatic and aromatic main‐chain units often produce atypical structures that cannot easily be accessed from purely aromatic or aliphatic sequences. We report solid‐state evidence that sequences comprising α‐amino acids and quinoline‐based monomers adopt conformations that combine the folding propensities of both components. Foldamers 2 and 3 having an XQQ repeat motif (X=α‐amino acid, Q=quinoline) were synthesized. Crystals of 2 (X=Phe, Q with an anionic side chain) obtained from water revealed an aromatic helix where amide groups belonging to the α‐amino acids created a hydrogen‐bond array typical of peptidic helices. Crystals of 3 (X=Ser, Q with a lipophilic side chain) obtained from organic solvents revealed a helix‐turn‐helix structure in which α‐amino acid side chains interfere with main‐chain hydrogen bonding. High sequence‐dependency of the conformation is typical of peptides but is shown here to include aromatic folding features.

Thermophysical Properties of Newly Synthesized Ammonium-Based Protic Ionic Liquids: Effect of Temperature, Anion and Alkyl Chain Length

Ionic liquids which are often classified as low melting point salts have received significant attention from research groups and industries to be used in a wide range of applications. Many of these applications require thorough knowledge on the thermophysical properties of the ionic liquids before utilizing their full potentials in various fields. In this work, a series of alkylammonium cation and carboxylate anion-based room temperature protic ionic liquids (PILs) were synthesized by varying length of alkyl chain of the cation from diethyl to dibutyl combined with pentanoate, hexanoate and heptanoate anions. These ammonium-based PILs named as diethylammonium pentanoate [DEA][C5], diethylammonium hexanoate [DEA][C6], diethylammonium heptanoate [DEA][C7], dibutylammonium pentanoate [DBA][C5], dibutylammonium hexanoate [DBA][C6] and dibutylammonium heptanoate [DBA][C7] were characterized using Nuclear Magnetic Resonance (NMR) spectroscopy. The thermophysical properties of the PILs namely density, dynamic viscosity and refractive index were measured and analyzed. Density, ρ and dynamic viscosity, η were determined at T = (293.15 to 363.15) K and refractive index, nD was measured at T = (293.15 to 333.15) K. The fitting parameters are proposed for the empirical correlations of density, dynamic viscosity and refractive index. The values of thermal expansion coefficient, αp, molecular volume, Vm, standard entropy, S° and lattice potential energy, Upot also have been calculated by using the specified equations. The thermal decomposition temperature, Td was also determined using a thermogravimetric analyzer (TGA) while the differential scanning calorimetry (DSC) technique provided the glass transition, Tg, melting point, Tm and crystallization, Tc temperatures of the PILs. The experimental results revealed that the dependency of the experimental values namely the ρ, η, nD, and Td on the alkyl chain of the anion, size of the cations and the temperature of measurement.

Investigation into the molecular design and plasticizing effectiveness of HPEG-based polycarboxylate superplasticizers in alkali-activated slag

In this study, a series of HPEG PCE polymers with different anionic charge density and side chain lengths was synthesized via free-radical copolymerization from acrylic acid and α-methallyl poly (ethylene glycol) ether (HPEG) as macromonomer. The resulting PCE polymers were characterized via Size Exclusion Chromatography (SEC) and anionic charge titration. Thereafter, a correlation between their molecular structures and dispersing effectiveness was established for alkali-activated slag. A broad variety of HPEG PCE polymers was found to work in the alkali-activated slag (AAS) system. Finally, the working mechanism for best performing polymer was investigated via adsorption measurements. It was concluded that HPEG PCEs of high anionicity, high Mw and short side chain length adsorb particularity high amounts on slag, thus providing enhanced dispersion capacity as compared to other HPEG polymers.

Preparation of Poly(Ionic Liquid) Particles with Anionic Side Chain by Dispersion Polymerization.

Micrometer-sized poly(ionic liquid) (PIL) particles with an anionic side chain, poly(1-butyl-3-methylimidazolium 3-sulfopropyl methacrylate) (poly([Bmim][SPMT])), are successfully prepared by dispersion polymerization at 60°C in ethanol/ethyl acetate (2/8, w/w) with poly(vinylpyrrolidone) as a stabilizer. However, the obtained particles do not maintain the particulate state during drying at room temperature due to poly([Bmim][SPMT])'s low glass-transition temperature, below room temperature. In order to prevent coalescence and maintain particle shape, a cross-linking monomer is added after the nucleation stage of dispersion polymerization. Moreover, Fourier-transform infrared spectroscopy (FT-IR) demonstrates cation exchange between the obtained particles and metal cations (Ag+ ).

Low viscosity lactam-based ionic liquids with carboxylate anions: Synthesis, characterization, thermophysical properties and mutual miscibility of ionic liquid with alcohol, water, and hydrocarbons

Low viscosity lactam-based ionic liquids (ILs) were synthesized by a neutralization reaction between a cyclic amide (lactam), such as γ-butyrolactam, ε-caprolactam, 12-aminododecanolactam, and 1-octyl-2-pyrrolidone with a Brønsted acid (acetic, butyric, or hexanoic acids), in a total of eight systems. From this experimental matrix, the following five ILs have been formed: γ-butyrolactam + acetic acid (BTA), γ-butyrolactam + butyric acid (BTB), and γ-butyrolactam + hexanoic acid (BTH); and, ε-caprolactam + acetic acid (CPA) and ε-caprolactam + hexanoic acid (CPH), all systems presenting low viscosity. All synthesized ILs were characterized by FTIR and 1H NMR spectroscopies. Volumetric and transport properties (density and viscosity), along with thermal decomposition and ionic conductivity analyses have been experimentally determined. Mutual miscibility of these ILs against n-butanol, water, toluene, heptane, ethylbenzene, styrene, cyclohexane, and cyclohexene systems were determined at 293.15 K and atmospheric pressure (P = 101.325 kPa). Cation and anion structures influence on the mixtures were discussed. Ionic liquids containing lower chain anions formed two phases with heptane and were completely miscible in aromatic hydrocarbons, water and n-butanol. While ionic liquids with higher chain anions showed partial miscibility only in water. The miscibility of n-heptane increases when the hydrophobic character of ILs increases, as observed for ILs produced from γ-butyrolactam (BTA, BTB, and BTH). ILs-solvents miscibilities are a function of the lactam ring chain, decreasing in aliphatic hydrocarbons and increasing in cyclic hydrocarbons.

Molecule-based nonlinear optical switch with highly tunable on-off temperature using a dual solid solution approach

Nonlinear optical switches that reversibly convert between on/off states by thermal stimuli are promising for applications in the fields of photoelectronics and photonics. Currently one main drawback for practical application lies in the control of their switch temperature, especially for the temperature range near room temperature. By mixed melting treatment, here we describe an alloy-like nonlinear optical switch with tunable switch temperature via a dual solid solution approach within the coordination polymer system. We initially prepare a coordination polymer (i-PrNHMe2)[Cd(SCN)3], which functions as a high-contrast thermoresponsive nonlinear optical switch originating from a phase transition at around 328 K. Furthermore, by taking advantage of a synergistic dual solid solution effect, the melt mixing of it with its analogue (MeNHEt2)[Cd(SCN)3], which features an unequal anionic chain templated by an isomeric ammonium, can afford coordination polymer solid solutions with switch temperatures that are tunable in a range of 273–328 K merely by varying the component ratio.

A Promising Phase Change Material with Record High Ionic Conductivity over a Wide Temperature Range of a Plastic Crystal Phase and Magnetic Thermal Memory Effect.

The emerging organic ion plastic crystals (OIPCs) are the most promising candidates used as solid-state electrolytes in a range of ionic devices. To endow an OIPC with additional functionality may create a new type of material for multifunctional devices. Herein, we present an ion plastic crystal, [EMIm][Ni(mnt)2] (1; [EMIm]+ = 1-ethyl-3-methylimidazolium and mnt2- = maleonitriledithiolate), and its crystal consists of twin dimeric chains of [Ni(mnt)2]- anions, embraced by [EMIm]+ cations. A crystal-to-plastic crystal transformation with a large latent heat that occurred at ∼367/337 K on heating/cooling is confirmed by the differential scanning calorimetry (DSC) technique. The plastic crystal phase in 1, characterized by variable temperature powder X-ray diffraction (PXRD) and optical microscopy images, spans a broad temperature range with ΔT ∼123/153 K on heating/cooling (DSC measurement), and the wide ΔT is relevant to an extra stable anion chain owing to the strong antiferromagnetic (AFM) interactions protecting the chain from collapse in the plastic crystal state. 1 is a single-component ion plastic crystal with a record high ion conductivity, 0.21 S·cm-1, at 453 K. The crystal-to-plastic crystal transformation in 1 is coupled to a bistable magnetic transition to give a multi-in-one multifunctional material. This study provides a creative thought for the design of OIPCs with striking thermal, electrical, and magnetic multifunctionality.

Designing silica xerogels containing RTIL for CO2 capture and CO2/CH4 separation: Influence of ILs anion, cation and cation side alkyl chain length and ramification

CO2 separation from natural gas is considered to be a crucial strategy to mitigate global warming problems, meet product specification, pipeline specs and other application specific requirements. Silica xerogels (SX) are considered to be potential materials for CO2 capture due to their high specific surface area. Thus, a series of silica xerogels functionalized with imidazolium, phosphonium, ammonium and pyridinium-based room-temperature ionic liquids (RTILs) were synthesized. The synthesized silica xerogels were characterized by NMR, helium pycnometry, DTA-TG, BET, SEM and TEM. CO2 sorption, reusability and CO2/CH4 selectivity were assessed by the pressure-decay technique. Silica xerogels containing IL demonstrated advantages compared to RTILs used as separation solvents in CO2 capture processes including higher CO2 sorption capacity and faster sorption/desorption. Using fluorinated anion for functionalization of silica xerogels leads to a higher affinity for CO2 over CH4. The best performance was obtained by SX- [bmim] [TF2N] (223.4 mg CO2/g mg/g at 298.15 K and 20 bar). Moreover, SX- [bmim] [TF2N] showed higher CO2 sorption capacity as compared to other reported sorbents. CO2 sorption and CO2/CH4 selectivity results were submitted to an analysis of variance and the means compared using Tukey's test (5%).

Halobismuth(III) salts with substituted aminopyridinium cations.

The crystal structures of six halobismuth(III) salts of variously substituted aminopyridinium cations display discrete mononuclear [BiCl6]3- and dinuclear [Bi2X10]4- anions (X = Cl or Br), and polymeric cis-double-halo-bridged [BinX4n]n- anionic chains (X = Br or I). Bis(2-amino-3-ammoniopyridinium) hexachloridobismuth(III) chloride monohydrate, (C5H9N3)2[BiCl6]Cl·H2O, (1), contains discrete mononuclear [BiCl6]3- and chloride anions. Tetrakis(2-amino-3-methylpyridinium) di-μ-chlorido-bis[tetrachloridobismuth(III)], (C6H9N2)4[Bi2Cl10], (2), tetrakis(2-amino-3-methylpyridinium) di-μ-bromido-bis[tetrabromidobismuth(III)], (C6H9N2)4[Bi2Br10], (3), and bis(4-amino-3-ammoniopyridinium) di-μ-chlorido-bis[tetrachloridobismuth(III)] dihydrate, (C5H9N3)2[Bi2Cl10]·2H2O, (4), incorporate discrete [Bi2X10]4- anions (X = Cl or Br), while catena-poly[2,6-diaminopyridinium [[cis-diiodidobismuth(III)]-di-μ-iodido]], {(C5H8N3)[BiI4]}n, (5), and catena-poly[2,6-diaminopyridinium [[cis-dibromidobismuth(III)]-di-μ-bromido]], {(C5H7N2)[BiBr4]}n, (6), include [BinX4n]n- anionic chains (X = Br or I). Structures (2) and (3) are isostructural, while that of (5) is a pseudomerohedral twin. There is no discernible correlation between the type of anionic species obtained and the cation or halide ligand used. The BiIII centres always have a slightly distorted octahedral geometry and there is a correlation between the Bi-X bond lengths and the number of classic N-H...X hydrogen bonds that the X ligand accepts, with a greater number of interactions corresponding with slightly longer Bi-X distances. The supramolecular networks formed by classic N-H...X hydrogen bonds include ladders, bilayers and three-dimensional frameworks.

Hexanuclear Niobium Cluster Compounds with Protonated N‐Base Cations

Octahedral clusters of the [M6X12] type offer numerous possibilities to form structural arrangements through different choices of bonding situations. In this paper a series of new cluster compounds of the transition metal niobium is described, which consist of the [Nb6Cl18]2–, and in one case [Nb6Cl18]3–, anion and protonated N‐base cations ([MIm‐H]+, [nPr3N‐H]+, [TMGu‐H]+, and [Tzn‐H]+). They all are prepared using water scavenger compounds [SOCl2 or (Ac)2O] under oxidising conditions, resulting in two‐electron (or one‐electron, respectively) oxidized cluster units with respect to the starting material [Nb6Cl14(H2O)4]·4H2O. Of five members of this group single‐crystal X‐ray structures were determined. The cluster anions exist in all structures as discrete units. The acidic H atoms of all N‐bases are hydrogen bonded to H acceptors, in 4 cases to outer, exo bonded Cl atoms of the cluster unit and in one case to the O atom of a co‐crystallized THF molecule. In [TMGu‐H]2[Nb6Cl18] chains of cluster anions exist hydrogen‐bonded through bridging [TMGu‐H]+ cations. ESI mass spectra of [MIm‐H]2[Nb6Cl18]·2SOCl2 and [TMGu‐H]2[Nb6Cl18] show the expected isotopic distribution patterns for the anions together with other peaks associated to chloride mass losses and/or reduction processes.