A new supramolecular tecton: the crucial impact of the polycation charge and geometry of H-bonds on the structure and properties of halometallates in the solid state

A new tricationic organic supramolecular tecton has been designed and synthesized. Contrary to known mono- and dicationic species, this new molecule, being a "three-way connector", allows assembling infinite supramolecular sheets and nets upon interaction with appropriate inorganic counterpart complex anions. In this work, triprotonated 6-amino-5,7-dimethyl-1,3-diazaadamantane, comprising two secondary and one primary nitrogen atoms, is used as a trication to form hybrid compounds with iodometallate anions by forming five hydrogen bonds at a time. It is shown that the bulky cation works simultaneously as a spacer and a connector, such that the positions of inorganic [MI6]3- anions (M = Sb or Bi) in the crystal structures are defined by five hydrogen bonds and are well-separated from each other. The latter is considered as a prerequisite for the hybrid compounds to exhibit optical properties originating from the undisturbed electronic structure of individual inorganic anions.

Ternary Complexes of BiI3/CuI and SbI3/CuI with Tetrahydrothiophene

Reactions of BiI3/CuI mixtures with tetrahydrothiophene (THT) in toluene produce 2-D sheet networks BiCu3I6(THT)n (n = 2, 3, or 4), depending on reaction conditions. All three structures are based on BiI6 octahedra, which share pairs of (μ2-I)2 with Cu3(THT)n units. BiCu3I6(THT)2 features Cu2(μ2-I)2 rhombs with close Cu···Cu interactions and is accompanied by formation of the very complex HBi3Cu12I22(THT)8. Reactions of SbI3/CuI with THT in toluene produced a SbCu3I6(THT)2 network shows Cu3(μ2-THT)2 units, like its Bi congener, but Cu6(μ2-I)6 barrels rather than rhombs. Isolated SbI3 units are stacked above the Cu6I6 barrels. A molecular compound, Sb3Cu3I12(THT)6 consists of a face-sharing Sb3I12 stack, in which the Cu-THT units are bonded in asymmetric fashion about the central SbI6. Metal-halide bonds were investigated via QTAIM and NLMO analyses, demonstrating that these bonds are largely ionic and occur between the Bi/Sb and I p orbitals. Hirshfeld analysis shows significant H···H and H···I interactions. Diffuse reflectance spectroscopy (DRS) reveals band edges for the Bi species of 1.71-1.82 eV, while those for the neutral Sb complexes are in the range of 1.94-2.06 eV. Mapping of the electronic structure via density of state calculations indicates population of antibonding Bi/Sb-I orbitals in the excited state.

Expanded graphite incorporated with Li4Ti5O12 nanoparticles as a high-rate lithium-ion battery anode

Due to their small interlayer spacing and a low lithiation potential close to Li+ deposition, current graphite anodes suffer from weak kinetics, and lithium deposition in a fast-charging process, hindering their practical application in high-power lithium-ion batteries (LIBs). In this work, expanded graphite incorporated with Li4Ti5O12 nanoparticles (EG/LTO) was synthesized via moderate oxidization of artificial graphite following a solution coating process. The EG/LTO has sufficient porosity for fast Li+ diffusion and a dense Li4Ti5O12 layer for decreased interface reaction resistance, resulting in excellent fast-charging properties. EG/LTO presented a high reversible capacity of 272.8 mA h g-1 at 3.74 A g-1 (10C), much higher than that of the original commercial graphite (50.1 mA h g-1 at 10C) and even superior to that of hard carbon. In addition, EG/LTO exhibited capacity retention rate of 98.4% after 500 cycles at 10C, demonstrating high structural stability during a long cycling process. This study provides a protocol for a solution chemistry method to prepare fast-charging graphite anode materials with high stability for high-power LIBs.

Synthesis, Crystal, and Electronic Structure of (HpipeH2)2[Sb2I10](I2), with I2 Molecules Linking Sb2X10 Dimers into a Polymeric Anion: A Strategy for Optimizing a Hybrid Compound's Band Gap

In searching for a tool for optimizing the band gap of a hybrid compound capable of serving as a light-harvesting material in lead-free photovoltaics, we synthesized a new polyiodoantimonate (HpipeH₂)₂[Sb₂I₁₀](I₂) and analyzed its crystal and electronic structure by application of X-ray crystal structure analysis, Raman and diffuse reflectance spectroscopies, and quantum chemical calculations. It was demonstrated that I₂ molecules link Sb₂I₁₀ edge-sharing octahedra into zig-zag chains, whereas the organic cations link inorganic anionic chains into a 3D structure featuring a complex pattern of covalent bonds and non-covalent interactions. Overall, these features provide the background for forming the electronic structure with a narrow band gap of 1.41 eV, therefore being a versatile tool for optimizing the band gap of a potential light-harvesting hybrid compound.

Nano-laponite/polymer composite as filtration reducer on water-based drilling fluid and mechanism study

In drilling deep complex formations, most drilling fluid additives have insufficient temperature and salt tolerance, resulting in the decline of drilling fluid performance. This study used 2-acrylamide-2-methylpropane sulfonic acid, acrylamide, dimethyl diallyl ammonium chloride and modified nano-laponite to synthesize a nanocomposite filtrate reducer (ANDP) with excellent temperature and salt resistance, which can maintain the performance of drilling fluid. The structure of ANDP was analysed by a transmission electron microscope and an infrared spectrometer. The thermal stability of ANDP was studied by thermogravimetric analysis. The performance of ANDP was evaluated in a water-based drilling fluid. The mechanism was analysed per clay particle size distribution, Zeta potential, filter cake permeability and scanning electron microscopy imaging. The results show that ANDP has good thermal stability and the expected molecular structure. The filtration of freshwater drilling fluid after ageing at 200°C is 10.4 ml and that of saturated brine drilling fluid is 6.4 ml after ageing at 150°C. Mechanism analysis suggests that the ANDP increases the thickness of clay particle hydration layer and maintains the colloidal stability of the drilling fluid. ANDP inhibits the agglomeration of clay particles and significantly reduces the filtration by forming dense mud cake.

An Organic-Inorganic Perovskitoid with Zwitterion Cysteamine Linker and its Crystal-Crystal Transformation to Ruddlesden-Popper Phase

We demonstrate synthesis of a new low-D hybrid perovskitoid (a perovskite-like hybrid halide structure, yellow crystals, P21/n space group) using zwitterion cysteamine (2-aminoethanethiol) linker, and its remarkable molecular diffusion-controlled crystal-to-crystal transformation to Ruddlesden-Popper phase (Red crystals, Pnma space group). Our stable intermediate perovskitoid distinctly differs from all previous reports by way of a unique staggered arrangement of holes in the puckered 2D configuration with a face-sharing connection between the corrugated-1D double chains. The PL intensity for the yellow phase is 5 orders higher as compared to the red phase and the corresponding average lifetime is also fairly long (143 ns). First principles DFT calculations conform very well with the experimental band gap data. We demonstrate applicability of the new perovskitoid yellow phase as an excellent active layer in a self-powered photodetector and for selective detection of Ni²⁺ via On-Off-On photoluminescence (PL) based on its composite with few-layer black phosphorous.

Co-luminescence in a zero-dimensional organic-inorganic hybrid antimony halide with multiple coordination units

Zero-dimensional (0D) organic-inorganic hybrid metal halides (OIMHs) containing multiple halometallate species (HMSs) have received extensive attention due to their capability to achieve multifunctional photophysical characteristics. Herein we report a lead-free 0D-OIMH compound, namely [Emim]8[SbCl6]2[SbCl5] (1, Emim = 1-ethyl-3-methylimidazolium), which is the first crystal containing two distinct mononuclear [SbXn]3-n units in one single structure. The optical absorption, temperature/excitation-variable photoluminescence (PL) and PL decay were studied. 1 exhibits a broad emission centered at 577 nm, which is analyzed to be a combination of the emissions from [SbCl6]3- and [SbCl5]2-. The structural effects including SbSb distances and polyhedral distortion of [SbXn]3-n on the PL of antimony-based 0D-OIMHs are discussed in detail. This work would provide guidance for constructing Sb-based 0D OIMHs composed of multiple halometallate species.