Structural Chemistry Research Articles

Crystal Structure and Li-Fe Order in Synthetic Mg(2-2x)LixFe3+x(SiO4) Olivine Structure.

Olivines are naturally occurring silicates consisting of isolated (SiO4)4- tetrahedra linked through M1O6 and M2O6 octahedra. In this study, we report the structural and crystal-chemical characterization of synthetic olivine crystals containing up to 25% Li-Fe3+ synthesized using the flux growth technique. Based on site scattering, <M1-O> and <M2-O> mean bond lengths, and charge neutrality of the chemical formula, we found a perfect ordering of Li and Fe3+ at the two distinct M1 and M2 sites. Unrestrained linear extrapolation to a hypothetical isostructural LiFe3+(SiO4) composition aligns well with the tabulated ionic radii of Li and Fe3+. Comparison made with the isostructural LiSc(SiO4) reveals that the Li-centered M2O6 octahedron has a significant capacity to distort in order to accommodate structural stresses, due to the relatively weak Li-O bond, while still achieving a bond valence sum that closely matches the formal charge of Li+. This behavior suggests the potential feasibility of an extended Li + Fe3+ for 2 Mg coupled substitution within the olivine structure. The reported structure of the LiFe3+(SiO4) endmember in the literature, despite its apparent matching of cell dimensions and space group with olivine, exhibits extremely unconventional crystal chemical features, raising questions about its validity. Given the importance of the suitability of Li-insertion in LiFeSiO4 as electrodes in rechargeable Li-ion batteries, further studies are needed to investigate its crystal structure and crystal chemistry.

Transition metal carbo chalcogenides: A novel family of 2D solid lubricants

Two-dimensional (2D) layered materials such as transition metal dichalcogenides (e.g., MoS2, WS2) and MXenes (e.g., Ti3C2Tx), as well as hybrids of these materials are the focus of current research in solid lubrication due to their outstanding performance. Transition metal carbo-chalcogenides (TMCCs), consisting of an MXene core and a TMD-like surface, represent an inherent combination of TMDs and MXenes without the need to construct hybrids out of the individual layers. Due to their layered structure and surface chemistry, favorable tribological properties can be expected from these novel materials. Here, multilayer Ta2S2C and Nb2S2C TMCCs are deposited solely as a powder onto a steel substrate and their tribological properties under linear sliding against different counterbodies, i.e., Al2O3, SiC, 100Cr6, and polytetrafluoroethylene (PTFE) are discussed. Advanced materials characterization techniques are used to detect the presence of TMCCs inside the wear tracks and to reveal their 2D structure within the tribofilm. Finally, density functional theory (DFT) simulations are used to unravel the easy shearability of TMCCs at the nanoscale. The results demonstrate the great potential of this new 2D material family, which also offers many possibilities for defined tuning of the solid-solid interface.

Pb2TeV2O10: A Lead Vanadate Tellurate with Wide Mid-IR Transparency and Large Birefringence Induced by Multiple Birefringence-Active Groups.

Birefringent materials as the key materials in laser science and technology have attracted continuous attention due to their ability to modulate polarized light. Herein, a new lead vanadate tellurate, Pb2TeV2O10, has been synthesized through the rational integration of different kinds of birefringence-active functional units. Pb2TeV2O10 features a unique two-dimensional (2D) [TeV2O10]∞ layered structure consisting of [VO6]7- and [TeO6]6- octahedra, and Pb2+ cations reside between the [TeV2O10]∞ layers. In addition, the rare edge-sharing mode of [VO6]7- and [TeO6]6- octahedra was found in this structure. Attributed to the high polarizability and appropriate arrangement of PbO8, VO6, and TeO6 units, Pb2TeV2O10 possesses a great theoretical birefringence of 0.275 at 532 nm, which is the largest among the vanadate tellurate family. The spectral tests also prove that Pb2TeV2O10 showcases a broad transparency window (439 nm-10 μm), covering an important mid-infrared (IR) atmospheric window (3-5 μm). In addition, in order to improve the transparency, alkali and alkaline earth metal cations were introduced by the substitution strategy, and then the compound K2Sr2Te2O9 was synthesized. It owns a shorter ultraviolet (UV) cutoff edge of 234 nm and a wider transparency window (234 nm-13.8 μm). The findings of Pb2TeV2O10 and K2Sr2Te2O9 enrich the structure chemistry of the tellurate family and provide new insights for designing new compounds with large optical anisotropy and wide spectral transparency.

Molecular insights into genistein-NSAID hybrids—synthesis, characterisation and DFT study

AbstractGenistein (GEN) is one of the pharmaceutically valuable phenolic compounds, which belongs to the isoflavone group of flavonoids and is a natural phytohormone found mainly in soybeans and red clover. It affects estrogen receptors, functioning as a selective estrogen receptor modulator (SERM) with anti-inflammatory and antioxidant activity. The presence of reactive phenolic groups in genistein provides an opportunity to expand its structure by introducing components responsible for anti-inflammatory properties. Such an innovative combination of a compound with anticancer and antioxidant potential with an anti-inflammatory compound (NSAID) may lead to interesting new derivatives with dual mechanisms of biological action. The synthesis and characterisation of genistein-NSAID hybrid compounds (ibuprofen, ketoprofen, naproxen, flurbiprofen) was conducted, together with a comprehensive structural and quantum chemistry DFT (density functional theory) computational analysis allowing the description of 1H-NMR and 13C-NMR spectroscopic properties of the starting compounds and the resulting hybrids. The study resulted in the formation of seven hybrid GEN-NSAID derivatives. In the case of ibuprofen, ketoprofen and flurbiprofen, a mixture of isomeric hybrid GEN-4’-NSAID and GEN-7-NSAID derivatives was obtained, whereas, for naproxen, only GEN-4’-NSAID was formed. The structural characteristics of the resulting compounds were determined using MS, IR, 1H-NMR and 13C-NMR spectroscopic methods. The most accurate DFT computational methods for predicting 1H-NMR and 13C-NMR spectra were also established with statistical parameters to assess their accuracy.

From [Ba3S][GeS₄] to [Ba₃CO₃][MS₄] (M = Ge, Sn): Enhancing optical anisotropy in IR birefringent crystals via functional group implantation

Birefringent crystals are crucial for manipulating light's phase and polarization, making them vital components in various optical devices. Traditionally, strategies for designing high-performance birefringent crystals have focused on modifying the parent structure. However, there are limited examples demonstrating how changing functional groups can effectively enhance birefringence (Δn), as such changes often significantly alter the crystal structure. In this study, we propose a “functional group implantation” strategy aimed at significantly improving birefringent performance within the chalcogenide system. This involves replacing the isotropic [S]2⁻ ions with anisotropic π-conjugated [CO₃]2⁻ groups. We validated this approach through comprehensive comparisons between the chalcogenide [Ba₃S][GeS₄] and the oxychalcogenide [Ba₃CO₃][MS₄] (where M ​= ​Ge and Sn), both of which adopt the same space group and feature the same arrangements of functional groups. Experimental characterization and theoretical calculations confirm that the [CO₃]2⁻ groups exhibit significantly greater polarization anisotropy than the [S]2⁻ groups. This difference leads to a marked increase in Δn in [Ba₃CO₃][MS₄] (ranging from 0.088 to 0.112 ​at 546 ​nm) compared to [Ba₃S][GeS₄] (0.021 ​at 546 ​nm). This finding not only broadens the structural chemistry of π-conjugated chalcogenides but also illustrates the potential of functional group implantation for designing infrared birefringent crystals with enhanced optical anisotropy.

Engineering the solvent-anion interactions of LiTFSI-based dual-salt electrolytes to sustain high-performance NCM622 cathodes

Electrolytes play a vital role in determining the performances of lithium-ion batteries (LIBs), especially the high-voltage LiNi0.6Co0.2Mn0.2O2 (NCM622) cathode in LiTFSI-based electrolytes. Herein, we report a high-capacity and stable NCM622 cathode that can be realized in LiTFSI-based (named T) carbonate electrolytes by tuning the intermolecular interactions using the added LiDFOB (named D). In the 1 M dual-salt electrolyte, the cathode failure and Al corrosion are suppressed in the 4.5 V-NCM622||Li batteries, because a uniform interfacial layer and weaker Li+-solvent interactions are built to inhibit the parasitic reactions. As a result, the capacity retention reaches 94.68% after 200 cycles and the 10 C-rate capacity is about 160 mA h g-1 in the 1 M T + D dual-salt electrolyte. Unlike the commonly used electrolyte, the FEC additive increases the de-solvation barrier and disturbs the cycle stability in (T + D) dual-salt systems. Density functional theory (DFT) calculation and nuclear magnetic resonance (NMR) spectra reveal that the additive FEC changes the solvent-solvent and solvent-anion interactions in the presence of T + D, which weakens the electrolyte-cathode compatibility. This work indicates that regulating the solvation structure and interfacial chemistry from solvent-solvent/anion interactions is promising for designing high-performance LIBs by using dual‐salt electrolytes.

A thiophene-based bisazomethine and its inclusion complex with permethylated β-cyclodextrin: Exploring structural characteristics and computational chemistry models

The condensation reaction of 5-bromo-2-thiophenecarboxaldehyde (1) with p-phenylene diamine (2) in 2:1 M ratio yielded the thiophene-based bisazomethine with bromine ends (3). The threading of 3 into the permethylated β-cyclodextrin (TMe-βCD) cavity allowed the formation of a new 3∙TMe-βCD inclusion complex. Spectral techniques like NMR, FTIR, XRD and ESI-MS were involved to assess the structural characteristics of 3 and 3∙TMe-βCD. The X-ray diffraction, DFT computations and molecular docking simulations were used to support the experimental findings. The surface morphology as well the ability to form stable monolayers at the air-water interface was further explored in detail. According to the molecular docking simulation, the 3∙TMe-βCD inclusion complex was stabilized through hydrophobic contacts and exhibited better surface parameters and thermal properties. With regard to the optical behavior, the 3∙TMe-βCD exhibited a higher green fluorescence with two decay times of 0.48 ns (87.40 %) and 3.48 ns (12.60 %). The surface pressure isotherms revealed the tendency of 3∙TMe-βCD to form highly organized monolayers from dilute DCM solution at the air-water interface. The Brewster angle microscopy (BAM) investigations also demonstrated a better homogeneity of the 3∙TMe-βCD layers than those of the reference 3. The comparative investigation of the photophysical and electrochemical properties highlighted the superiority of the encapsulated 3∙TMe-βCD compound that are of fundamental importance in organic electronics.

Structural chemistry of organically templated transition metal phosphite chlorides, [BH2][M(H2PO3)2Cl2] (B = diamine, M = Mn–Ni, Cd) as new analogs of “hydroselenite halides”

Structural chemistry of organically templated transition metal phosphite chlorides, [BH2][M(H2PO3)2Cl2] (B = diamine, M = Mn–Ni, Cd) as new analogs of “hydroselenite halides”

Multilayered alginate–hydrogel-functionalized zeolite based on ionic cross-linking composed with a certain Ca2+ and Mg2+ ratio for ammonium adsorption

To enhance ammonium removal in wastewater treatment, a novel adsorbent, multilayered ionic cross–linked alginate–hydrogel–metal-coated zeolite (Al-H-M-Z), was synthesized. Essential divalent cations, 2.60 mmol of Ca2+ and Mg2+, were incorporated into Al-H-M-Z (10 g) in a Ca2+:Mg2+ ratio of 0.73:1.85, facilitating strong alginate–polymer interactions and significantly enhancing the adsorption efficiency. Langmuir and Freundlich isotherm analyses revealed that Al-H-M-Z had a maximum adsorption capacity of 56.5 ± 8.78 mg g−1 and an adsorption intensity of 0.703 ± 0.122, which were 7.24-fold and 1.59-fold higher than those of natural zeolite (7.80 ± 1.09 mg g−1 and 0.444 ± 0.254), respectively. These enhanced properties are attributed to the modified structural and surface chemistry. The Al-H-M-Z coating exhibited a 4.76-fold increase in surface area (3.91 m2 g−1), an 8.94-fold increase in micropore volume (17.8 × 10−3 cm3 g−1), and a 4.22-fold increase in pore diameter (4.14 nm) when compared to the traditional Al-only coating. For applicability, Al-H-M-Z and Z achieved ammonium removal rates of 7.94% and 5.61%, respectively, in actual fish farm wastewater, representing a 1.41-fold improvement in adsorption efficiency after the coating process.

Synthesis, Structure and Properties of Core‐Modified Calixporphyrinoids

AbstractCalix[n]porphyrinoids containing both sp2 and sp3 meso‐carbons can bind metals like porphyrinoids and anions like calix[n]pyrroles. Thus, calix[n]porphyrinoids are hybrid macrocycles of porphyrinoids and calix[n]pyrroles. The core‐modified calix[n]porphyrinoids resulted by replacing one or more pyrroles of calix[n]porphyrinoids with different heterocycles or carbacycles that possesses very attractive structural, spectral, and coordination properties. For the past two decades, several different types of core‐modified calix[n]porphyrinoids in which one or more pyrroles were replaced with other heterocycles such as thiophene, selenophene, tellurophene, silole, phosphole, pyridine, etc and carbacycles such as m/p‐phenylene have been synthesized and explored their structure, metal coordination and anion sensing properties. This review describes different synthetic strategies used for the synthesis of various types of core‐modified calix[4]phyrins and expanded calix[n]phyrins and discusses their key structural aspects, properties, coordination chemistry and applications.

In vitro and ex vivo metabolism of chemically diverse fructans by bovine rumen Bifidobacterium and Lactobacillus species

BackgroundInulin and inulin-derived fructooligosaccharides (FOS) are well-known prebiotics for use in companion animals and livestock. The mechanisms by which FOS contribute to health has not been fully established. Further, the fine chemistry of fructan structures from diverse sources, such as graminan-type fructans found in cereal crops, has not been fully elucidated. New methods to study fructan structure and microbial responses to these complex carbohydrates will be key for evaluating the prebiotic potency of cereal fructans found in cattle feeds. As the rumen microbiome composition is closely associated with their metabolic traits, such as feed utilization and waste production, prebiotics and probiotics represent promising additives to shift the microbial community toward a more productive state.ResultsWithin this study, inulin, levan, and graminan-type fructans from winter wheat, spring wheat, and barley were used to assess the capacity of rumen-derived Bifidobacterium boum, Bifidobacterium merycicum, and Lactobacillus vitulinus to metabolize diverse fructans. Graminan-type fructans were purified and structurally characterized from the stems and kernels of each plant. All three bacterial species grew on FOS, inulin, and cereal crop fructans in pure cultures. L. vitulinus was the only species that could metabolize levan, albeit its growth was delayed. Fluorescently labelled polysaccharides (FLAPS) were used to demonstrate interactions with Gram-positive bacteria and confirm fructan metabolism at the single-cell level; these results were in agreement with the individual growth profiles of each species. The prebiotic potential of inulin was further investigated within naïve rumen microbial communities, where increased relative abundance of Bifidobacterium and Lactobacillus species occurred in a dose-dependent and temporal-related manner. This was supported by in situ analysis of rumen microbiota from cattle fed inulin. FLAPS probe derived from inulin and fluorescent in situ hybridization using taxon-specific probes confirmed that inulin interacts with Bifidobacteria and Lactobacilli at the single-cell level.ConclusionThis research revealed that rumen-derived Bifidobacteria and Lactobacilli vary in their metabolism of structurally diverse fructans, and that inulin has limited prebiotic potential in the rumen. This knowledge establishes new methods for evaluating the prebiotic potential of fructans from diverse plant sources as prebiotic candidates for use in ruminants and other animals.

Characterization of lignin-degrading enzyme PmdC, which catalyzes a key step in the synthesis of polymer precursor 2-pyrone-4,6-dicarboxylic acid

Pyrone-2,4-dicarboxylic acid (PDC) is a valuable polymer precursor that can be derived from the microbial degradation of lignin. The key enzyme in the microbial production of PDC is CHMS dehydrogenase, which acts on the substrate 4-carboxy-2-hydroxymuconate-6-semialdehyde (CHMS). We present the crystal structure of CHMS dehydrogenase (PmdC from Comamonas testosteroni) bound to the cofactor NADP, shedding light on its three-dimensional architecture, and revealing residues responsible for binding NADP. Using a combination of structural homology, molecular docking, and quantum chemistry calculations we have predicted the binding site of CHMS. Key histidine residues in a conserved sequence are identified as crucial for binding the hydroxyl group of CHMS and facilitating dehydrogenation with NADP. Mutating these histidine residues results in a loss of enzyme activity, leading to a proposed model for the enzyme’s mechanism. These findings are expected to help guide efforts in protein and metabolic engineering to enhance PDC yields in biological routes to polymer feedstock synthesis.

Natural products: A potential immunomodulators against inflammatory-related diseases.

The incidence and prevalence of inflammatory-related diseases (IRDs) are increasing worldwide. Current approved treatments for IRDs in the clinic are combat against inhibiting the pro-inflammatory cytokines. Though significant development in the treatment in the IRDs has been achieved, the severe side effects and inefficiency of currently practicing treatments are endless challenge. Drug discovery from natural sources is efficacious over a resurgence and also natural products are leading than the synthetic molecules in both clinical trials and market. The use of natural products against IRDs is a conventional therapeutic approach since it is a reservoir of unique structural chemistry, accessibility and bioactivities with reduced side effects and low toxicity. In this review, we discuss the cause of IRDs, treatment of options for IRDs and the impact and adverse effects of currently practicing clinical drugs. As well, the significant role of natural products against various IRDs, the limitations in the clinical development of natural products and thus pave the way for development of natural products as immunomodulators against IRDs are also discussed.

Pre-deformation assisted fabrication of bulk Nd2Fe14B/α-Fe nanocomposites with high energy density

For Nd2Fe14B/α-Fe nanocomposite magnets, which exhibit great superiority in theoretical energy products, it is a great challenge to obtain controlled nano-scale microstructural features while eliminating the harmful metastable phases due to the general metastable fabrication methods. Here, we report a strategy to control the nano-scale features and simultaneously eliminate metastable phases for Nd2Fe14B/α-Fe nanocomposites through low-temperature pre-deformation of amorphous alloys combined with subsequent thermal annealing. The resultant bulk Nd2Fe14B/α-Fe nanostructure exhibits desired ultrafine grain sizes, ∼20 nm for soft-magnetic α-Fe phase with a high fraction of Vα-Fe ≈ 30 wt% and ∼33 nm for hard-magnetic Nd2Fe14B phase. The desired microstructure results in a larger coercivity (Hci = 4.1 kOe) and higher saturation magnetization (Ms = 1.51 T) compared to those (Hci = 3.3 kOe and Ms = 1.35 T) of the counterpart without pre-deformation, contributing to a high energy density of 26.3 MGOe. This energy density is 200% larger than that of the counterpart without pre-deformation and far beyond that (around 20 MGOe) of previously reported bulk Nd2Fe14B/α-Fe nanocomposites with Vα-Fe ≥ 20 wt%. The superior property stems from the purposely introduced low-temperature pre-deformation that changed the structure and local chemistry of the amorphous alloy, facilitating the decomposition of harmful metastable phases and the formation of Nd2Fe14B phase during annealing processes, which lowers the temperature, from 750 to 700 °C for producing the Nd2Fe14B/α-Fe nanostructure and thus yields ultrafine nanograins. These results demonstrate an effective means to prepare high-performance bulk Nd2Fe14B/α-Fe nanocomposite magnets.

Structural Chemistry Simulation Experiments: A Case Study on Conjugated Alkene Molecules

As a core branch of chemistry, structural chemistry presents challenges in teaching due to its theoretical constructs and complex mathematical derivations. The application of quantum mechanics is particularly difficult for students. This paper analyzes the limitations of traditional experimental teaching and proposes simulation experiments as an effective supplementary method. Simulation experiments, by reducing costs, improving safety, and enhancing intuitiveness, help students deeply understand the theoretical knowledge of structural chemistry and cultivate their critical thinking and problem-solving skills. This study designs a series of simulation experiment teaching activities aimed at enhancing students' understanding of the structural characteristics of conjugated alkene molecules and their impact on molecular properties. Through case analysis, interactive discussions, and feedback evaluation, the study demonstrates the advantages of simulation experiments in improving student engagement, knowledge mastery, and practical abilities. Additionally, it points out the shortcomings of simulation experiments in terms of authenticity and technological dependence and proposes corresponding improvement suggestions. Finally, it emphasizes the importance of combining practical experimental operations with cultivating students' autonomous learning abilities, aiming to provide a more comprehensive strategy for structural chemistry teaching.

Structure Distortion Endows Copper Nanoclusters with Surface-Active Uncoordinated Sites for Boosting Catalysis.

The utilization of structure distortion to modulate the electronic structure and alter catalytic properties of metallic nanomaterials is a well-established practice, but accurately identifying and comprehensively understanding these distortions present significant challenges. Ligand-stabilized metal nanoclusters with well-defined structures serve as exemplary model systems to illustrate the structure chemistry of nanomaterials, among which few studies have investigated nanocluster models that incorporate structural distortions. In this work, a novel copper hydride nanocluster, Cu42(PPh3)8(RS)4(CF3COO)10(CH3O)4H10 (Cu42; PPh3 is triphenylphosphine and RSH is 2,4-dichlorophenylthiol), with a highly twisted structure has been synthesized in a simple way. Structural analysis reveals Cu42 comprises two Cu25 units that are conjoined in a nearly orthogonal manner. The dramatic distortion in the metal framework, which is driven by multiple interactions from the surface ligands, endows the cluster with a rich array of uncoordinated metal sites on the surface. The resulting cluster, as envisioned, exhibits remarkable activity in catalyzing carbonylation of anilines. The findings from this study not only provides atomically precise insights into the structural distortions that are pertinent to nanoparticle catalysts but also underscores the potential of structurally distorted NCs as a burgeoning generation of catalysts with precise structures and outstanding performances that can be tailored for specific functions.

LiNa2Ca8B12O24F6Cl and Li1.2Na2.8B6O11: A Case of Cation-Induced Birefringence Enhancement via Dimensional Changes of Highly Polymerized [B12O24] Motifs.

Borates, due to their structural chemistry diversity and exceptional performance, are premier material systems for investigating UV optical crystals. The B-O anionic groups with high polymerization (B ≥ 6) are much less in the borate-based system, which is worthy of further research. Herein, cations with different radii and proportions are introduced to borate system, and two new highly polymerized borates, LiNa2Ca8B12O24F6Cl (LNCBFC) and Li1.2Na2.8B6O11 (LNBO) were designed and synthesized successfully. LNCBFC possesses commonly isolated high-symmetry [B12O24] groups, while the structure of LNBO contains an unprecedented 1∞[B12O22] chain constructed by [B12O24] groups. Owing to the orientation of the functional motifs in the chain structure, LNBO displays an enhanced birefringence, which is about 25 × higher than that of LNCBFC and retains a short UV cutoff edge (< 200 nm). Even more significantly, a discussion of the cationic modulation of [B12O24]-based compounds and the patterns of isolated [BnO2n] motifs consisting of B-O rings was carried out by reviewing previous studies and existing borates. This work puts forward a decent structure design and property regulation strategy for highly polymerized borates.

Chemically Bonded Biphase Coating of Ni-Rich Layered Oxides with Enhanced High-Voltage Tolerance and Long-Cycle Stability.

Stabilizing the crystalline structure and surface chemistry of Ni-rich layered oxides is critical for enhancing their capacity output and cycle life at a high cutoff voltage. Herein, we adopted a simple one-step solid-state method by directly sintering the Ni0.9Co0.1(OH)2 precursor with LiOH and Ta2O5, to simultaneously achieve the bulk material synthesis of LiNi0.9Co0.1O2 and in situ construction of a rock-salt Ta-doped interphase and an amorphous LiTaO3 outer layer, forming a chemically bonded surface biphase coating on LiNi0.9Co0.1O2. Such a cathode architectural design has been demonstrated with superior advantages: (1) eliminating surface residual alkali, (2) strengthening the layered oxygen lattice, (3) suppressing bulk-phase transformation, and (4) facilitating Li-ion transport. The obtained cathode exhibits excellent electrochemical performance, including a high initial reversible capacity of 180.3 mAh g-1 at 1.0 C with 85.5% retention after 300 cycles (2.8-4.35 V) and a high initial reversible capacity of 182.5 mAh g-1 at 0.2 C with 87.6% retention after 100 cycles (2.8-4.5 V). Notably, this facile and scalable electrode engineering makes Ni-rich layered oxides promising for practical applications.

Induced π–complexation properties of smectites impregnated by Ni, Cu and Ag transition metals: The highly efficient styrene uptake

Two natural smectite minerals (montmorillonite and beidellite) differing in structural charge location were impregnated with varying amounts of transition metals: Ni(II), Cu(I) or Ag(I). The modification aimed to increase the affinity of the minerals towards styrene vapors. The structure, texture, chemical composition and surface chemistry of the materials were studied by XRD, FTIR, Raman, N2 adsorption/desorption, XRF and XPS. The experiments examined the influence of the starting smectite and the type of introduced metal on styrene adsorption efficiency. The styrene uptake mechanisms were investigated through solid state analysis and supported by DFT calculations. The study demonstrated that the small content of introduced metals (<2% wt.) substantially increased styrene uptake (∼200–350% wt.) surpassing values reported for surfactant-intercalated smectites (∼40–80% wt.) and activated carbons (∼30% wt.). This enhancement was attributed to the π-complexation between dispersed d-block metals and π-electron-rich styrene molecules, subsequently leading to polystyrene formation. The DFT calculations were consistent with experimental findings, indicating a higher affinity of the raw beidellite towards styrene than the raw montmorillonite connected to the charge location. Moreover, the observed trends in calculated adsorption energies and lengths of weak hydrogen bonds allowed to explain a significant adsorption increase observed for the Ni- and Cu-impregnated montmorillonite-based materials.

Structural Chemistry of C-N Axially Chiral Compounds.

In the last several years, atropisomers owing to the rotational restriction around a C-N single bond (C-N axially chiral compounds) have attracted significant attention in the field of synthetic organic chemistry. In particular, the highly enantioselective synthesis of various C-N axially chiral compounds and their application to asymmetric reactions have been reported by many groups. On the other hand, studies on the structural chemistry of C-N axially chiral compounds have attracted scant attention in comparison with synthetic studies. For over 25 years, our group has explored asymmetric synthesis of C-N axially chiral compounds and their synthetic application. In the course of these synthetic studies, we found several notable structural properties in relation to the C-N bond rotation and an association of enantiomers (the relationship between the rotational stability and the structure or electronic effect, the chirality-dependent halogen bond, and the self-disproportionation of enantiomers). Furthermore, on the basis of these structural properties, the development of acid-mediated molecular rotors and the synthesis of isotopic atropisomers possessing high stereochemical purity and rotational stability were achieved. Through this Perspective, I wish to make the chemistry community aware that C-N axially chiral compounds are attractive molecules from the viewpoints of both synthetic organic chemistry and structural chemistry.