Lone Pair Research Articles

Passivating Defects via Retarding the Reaction Rate of FAI and PbI2 Enables Stable Perovskite Solar Cells.

The two-step sequential deposition strategy has garnered widespread usage in the fabrication of high-performance perovskite solar cells based on FAPbI3. However, the rapid reaction between FAI and PbI2 during preparation often leads to incomplete reactions, reducing the device efficiency and stability. Herein, we introduced a multifunctional additive, 2-thiophenyl trifluoroacetone (TTA), into the FAI precursor. The incorporation of TTA has proven to be highly effective in slowing the reaction rate between FAI and PbI2, resulting in increased perovskite formation and improved efficiency and stability of the devices. TTA's CF3 groups interact with FAI via hydrogen bonding, effectively suppressing FA+ defects. The S and C═O groups share lone pair electrons with uncoordinated Pb2+, leading to a reduction in perovskite film defects and suppressing nonradiative recombination. Additionally, the CF3 groups impart hydrophobicity, protecting the perovskite film from moisture-induced erosion. As a result, the TTA-modified perovskite film achieves a Champion efficiency of 23.42% compared to the control's 21.52, with 20.58% efficiency for a 25 cm2 solar module. Remarkably, the unencapsulated Champion device retains 86% of its initial PCE after 1080 h under dark conditions (60 ± 5 °C, 35 ± 5% RH), indicating enhanced long-term stability. These findings offer a promising and cost-effective tactic for high-quality perovskite film fabrication.

Spiro-Bifluorene-Cored Dopant-Free Conjugated Polymeric Hole-Transporting Materials Containing Passivation Parts for Inverted Perovskite Solar Cells.

Two spiro-bifluorene-based dopant-free HTMs (X22 and X23) have been synthesized by facilely condensing spiro-bifluorene diamine with 3,4-ethylenedioxythiophene (EDOT)-5,7-dicarbonyl dichloride and 2,3,5,6-tetrafluoro-terephthaloyl dichloride, respectively. In the X22 molecule, lone pairs of electrons on the sulfur (S) and oxygen (O) functional groups interact with the perovskite materials. The hole mobility (μh) of X22 (3.9 × 10-4 cm2 V-1 S1-) is more than twice that of X23 (1.4 × 10-4 cm2 V-1 S1-). The conductivity (σ0) of X22 is 2.73 × 10-4 S cm-1, which is also higher than that of X23 (2.39 × 10-4 S cm-1). The EDOT moiety benefits the contact angle of CH3NH3PbI3 precursor solutions on HTMs as low as 24°. The X22-based device with an indium-doped tin oxide/hole transport material (HTM)/CH3NH3PbI3/phenyl-C61-butyric acid methyl ester (PC61BM)/bathocuproine/Ag structure achieves a power conversion efficiency (PCE) of 19.18%. The PCE of the device based on X23 containing fluorine is 18.70%, and the contact angle between HTM and the perovskite precursor solution is 32°. The X22- and X23-based devices at ambient temperature (≈25 °C) in N2 retain 86% and 79% of the initial PCE after 150 days. The effect of S, O, and F heteroatoms plays an important role in the side chain modification of HTMs, improving defect passivation in HTM/CH3NH3PbI3 interfaces by multiple functional groups.

How electrons still guard the space: Electron number distribution functions based on QTAIM∩ELF intersections.

Despite the importance of the one-particle picture provided by the orbital paradigm, a rigorous understanding of the spatial distribution of electrons in molecules is still of paramount importance to chemistry. Considerable progress has been made following the introduction of topological approaches, capable of partitioning space into chemically meaningful regions. They usually provide atomic partitions, for example, through the attraction basins of the electron density in the quantum theory of atoms in molecules (QTAIM) or electron-pair decompositions, as in the case of the electron localization function (ELF). In both cases, the so-called electron distribution functions (EDFs) provide a rich statistical description of the electron distribution in these spatial domains. Here, we take the EDF concept to a new fine-grained limit by calculating EDFs in the QTAIM ∩ ELF intersection domains. As shown in AHn systems based on main group elements, as well as in the CO, NO, and BeO molecules, this approach provides an exquisitely detailed picture of the electron distribution in molecules, allowing for an insightful combination of the distribution of electrons between Lewis entities (such as bonds and lone pairs) and atoms at the same time. Besides mean-field calculations, we also explore the impact of electron correlation through Hartree-Fock (HF), density functional theory (DFT) (B3LYP), and CASSCF calculations.

Structural Phase Transition in 0D (3,5-DMP)2Bi1-xSbxCl5 Metal Halides: Expression of the Lone Pair Effect and Polyhedral Distortion.

Low-dimensional Bi/Sb-based organic-inorganic metal halides (OIMHs) have attracted immense attention from the research community because of their structural diversity and efficient luminescence properties. Further understanding of the relationship between the structure and luminescence properties of these materials is of utmost importance for tuning the luminescence properties for various practical applications. Herein, we have synthesized two lead-free Bi/Sb-based novel OIMHs, (3,5-DMP)2BiCl5 and (3,5-DMP)2SbCl5 [(3,5-DMP) = 3,5-dimethylpiperidine], with zero-dimensional (0D) structures and crystallizing in triclinic (P space group) and monoclinic (P21/c space group) crystal systems, respectively. Both the compounds behave as typical semiconductors with indirect optical band gaps of 3.34 and 3.36 eV for pristine Bi and Sb compounds. These compounds exhibit higher environmental and thermal stability at ambient conditions. Gradual substitution of Sb at the Bi site in (3,5-DMP)2Bi1-xSbxCl5 resulted in the introduction of structural strain due to the significant expression of the lone pair effect, thus leading to a structural transition from the triclinic to monoclinic phase. The effect of the structural phase transition on the optical properties is also studied in (3,5-DMP)2Bi1-xSbxCl5. This work may offer new direction and guidance for exploring various 0D hybrid metal halides and tuning the structures for improvement in the luminescence properties.

Water Arrangements upon Interaction with a Rigid Solute: Multiconfigurational Fenchone-(H2O)4-7 Hydrates.

Insight into the arrangements of water molecules around solutes is important to understand how solvation proceeds and to build reliable models to describe water-solute interactions. We report the stepwise solvation of fenchone, a biogenic ketone, with 4-7 water molecules. Multiple hydrates were observed using broadband rotational spectroscopy, and the configurations of four fenchone-(H2O)4, three fenchone-(H2O)5, two fenchone-(H2O)6, and one fenchone-(H2O)7 complexes were characterized from the analysis of their rotational spectra in combination with quantum-chemical calculations. Interactions with fenchone deeply perturb water configurations compared with the pure water tetramer and pentamer. In two fenchone-(H2O)4 complexes, the water tetramer adopts completely new arrangements, and in fenchone-(H2O)5, the water pentamer is no longer close to being planar. The water hexamer interacts with fenchone as the least abundant book isomer, while the water heptamer adopts a distorted prism structure, which forms a water cube when including the fenchone oxygen in the hydrogen bonding network. Differences in hydrogen bonding networks compared with those of pure water clusters show the influence of fenchone's topology. Specifically, all observed hydrates except one show two water molecules binding to fenchone through each oxygen lone pair. The observation of several water arrangements for fenchone-(H2O)4-7 complexes highlights water adaptability and provides insight into the solvation process.

Ligand-modified nanoparticle surfaces influence CO electroreduction selectivity

Improving the kinetics and selectivity of CO2/CO electroreduction to valuable multi-carbon products is a challenge for science and is a requirement for practical relevance. Here we develop a thiol-modified surface ligand strategy that promotes electrochemical CO-to-acetate. We explore a picture wherein nucleophilic interaction between the lone pairs of sulfur and the empty orbitals of reaction intermediates contributes to making the acetate pathway more energetically accessible. Density functional theory calculations and Raman spectroscopy suggest a mechanism where the nucleophilic interaction increases the sp2 hybridization of CO(ad), facilitating the rate-determining step, CO* to (CHO)*. We find that the ligands stabilize the (HOOC–CH2)* intermediate, a key intermediate in the acetate pathway. In-situ Raman spectroscopy shows shifts in C–O, Cu–C, and C–S vibrational frequencies that agree with a picture of surface ligand-intermediate interactions. A Faradaic efficiency of 70% is obtained on optimized thiol-capped Cu catalysts, with onset potentials 100 mV lower than in the case of reference Cu catalysts.

Catalytic Pyrolysis of Waste-Printed Circuit Boards Using a Cu/Fe Bimetal Synergistic Effect to Enhance Debromination

Deep and efficient debromination is a critical step in achieving environmentally friendly recycling and ensuring the sustainability of waste-printed circuit boards (WPCBs) because of their high toxicity and carcinogenicity. To this end, this study used a copper–iron (Cu/Fe) bimetal as a debromination agent to remove bromides from WPCBs using in situ catalytic pyrolysis technology. The results show that the maximum debromination efficiency was 97.14% under the following conditions: a Cu mole ratio of 0.20 (Cu/Fe-0.20), a Cu/Fe-0.20 dosage of 0.4, a pyrolysis temperature of 600 °C, and a retention time of 10 min. The main bromine species in pyrolysis oil and gas were bromophenol, bromomethane, HBr, and Br2. The conversion of bromine species and the debromination of the Cu/Fe-0.20 bimetal were analyzed in real time using a thermogravimetry-coupled Fourier transform infrared and mass spectrometer (TG-FTIR-MS). Using the Cu/Fe bimetal synergistic effect, we determined that the debromination mechanism could be used for bromide conversion and fixing. The Cu in the Cu/Fe-0.20 transformed the organic Br (bromophenol and bromomethane) into inorganic Br (HBr and Br2) by providing empty orbitals for lone pairs of electrons. Then, the generated HBr and Br2 reacted with Fe in the Cu/Fe-0.20 and were fixed in pyrolysis residue. This study provides theoretical support and a practical method for WPCB deep debromination and recycling.

Trends in GeTe Thermoelectrics: From Fundamentals to Applications

AbstractGermanium telluride (GeTe) with ultrafast ferroelectric transition, Rashba‐like electronic transport, and anomalous phonon anharmonicity are historically studied for potential memorizing and thermoelectric applications. Due to recent breakthroughs in spintronics, valleytronics, orbitronics, pre‐eminent GeTe thermoelectrics have re‐attracted enormous interest from both academia and industries, with increasing reports of significant figure‐of‐merit over 2.7 and the maximum efficiency of up to 17.0%. Here, the emerging trends in advancing GeTe thermoelectrics, starting from fundamentals of phase transformation, crystal structure, bonding mechanisms, and transport characteristics, with a highlight on the roles of Ge_4s2 lone pairs, are timely overviewed. Technical insights in synthesis, characterization, property measurement, and computation are then summarized. After that, several innovative strategies for increasing the figure‐of‐merit, including entropy engineering, nanostructuring, and hybridization, which will further benefit near‐room‐temperature and n‐type performance, are examined. Moreover, high‐density and high‐efficiency devices with broad working temperatures are discussed as a result of rational configurational and interfacial design. In the end, perspective remarks on the challenges and outlook envisaging for next‐generation GeTe thermoelectrics, which will play a prominent role in future energy and environmental landscapes, are provided.

Metastable 2D amorphous Nb2O5 for aqueous supercapacitor energy storage

Nb2O5 is a promising electrode material of energy storage due to its high specific capacity and phase transition resistance. However, the facile generation of niobic acid poses a challenge, hindering controlled growth and impeding improvements in electrical conductivity and structural stability, especially in realizing two-dimensional (2D) Nb2O5. Herein, we have discerned that the addition of hexamethylenetetramine (HMTA) in ethanol solvent facilitates the controlled and restricted growth of metastable 2D amorphous Nb2O5 (a-Nb2O5) within graphene domains. Nitrogen atoms within HMTA, rich in lone pair electrons, strongly interact with niobium ions, promoting 2D amorphous growth on graphene interface. This unique 2D amorphous interface offers high surface area, enhanced electron mobility, rapid ion transport, and superior structural stability compared to crystalline counterparts. The prepared metastable 2D a-Nb2O5/rGO electrode exhibits unprecedented cycle life in aqueous asymmetric supercapacitor. This confined growth strategy offers a novel approach for the innovative design of metastable 2D materials.

N-doped carbon decorated Na3V2(PO4)3@NC composite derived from melamine as cathode material for high-rate and ultralong-life sodium-ion batteries

Sodium superionic conductor (NASICON) Na3V2(PO4)3 (NVP) is one of the most promising cathode materials for Sodium ion batteries (SIBs). However, its low electronic conductivity makes the cycle and rate performance less ideal. Increasing the electronic conductivity of NVP by carbon coating has been more and more confirmed, especially for N-doped carbon. Here, in-situ melamine-derived N-doped carbon-coated Na3V2(PO4)3@NC (NVP@NC) by hydrothermal-assisted sol-gel method is prepared. The introduction of N has no effect on the original NASICON structure of NVP@C, but the melamine addition amount affected the intensity of the diffraction peak from different NVP@NC samples. The NVP@NC shows superior cycling and rate performance. In the NVP@NC-2 sample with nC3N6H6/nNVP = 2, its discharge capacity maintains 106.82 mAh·g−1 at the 500th cycle at 0.2 C. The reversible capacities at 10 and 20 C are 90.5 and 85.0 mAh·g−1 with capacity retention of 81.2% and 76.3%, respectively. The zero-band gap of NVP@NC-2 through first-principles calculations means the ionic conductivity of NVP@C is greatly enhanced after N doping. The addition of the N element to the carbon layer contributes a pair of lone pairs of electrons to the matrix carbon and introduces certain active sites and defects. The reason for the improved electrochemical performance is that the N-doped carbon layer (NC) enables the expansion and deformation of the crystal structure to be controlled, increasing the Na+ diffusion coefficient and the electrical conductivity of NVP.

The Spin-Orbit Effect on the Electronic Structures, Refractive Indices, and Birefringence of X2PO4I (X = Pb, Sn, Ba and Sr): A First-Principles Investigation.

Introducing post-transition metal cations is an excellent strategy for enhancing optical properties. This paper focuses on four isomers, namely the X2PO4I (X = Pb, Sn, Ba, and Sr) series. For the first time, the paper's attention is paid to the changes in electronic structure, as well as refractive indices and birefringence, with and without the inclusion of spin-orbit effects in this series. The first-principles results show that spin-orbit effects of the 5p and 6p states found in these compounds lead to splitting of the bands, narrowing of the band gap, enhancement of the lone-pair stereochemistry, and enhancement of the refractive indices and birefringence. Moreover, a comparison of the lone-pair electron phosphates, X2PO4I (X = Pb and Sn), and the isomeric alkaline earth metal phosphates, X2PO4I (X = Ba and Sr), reveals that changes in the band structure have a greater effect on the enhancement of the birefringence than the slight enhancement of the lone-pair stereochemical activity. This study has important implications for a deeper understanding of the optical properties of crystals and the design of novel optical materials.

Comparative study of 4-((4-aminophenyl)diazenyl)-2-((2-phenylhydrazono)methyl)phenol and N-(4-((4-hydroxy-3-((2-phenylhydrazono)methyl)phenyl)diazenyl)phenyl)acetamide - DFT method

Theoretical calculation of 4-((4-aminophenyl)diazenyl)-2-((2-phenylhydrazono)methyl) phenol (1) and N-(4-((4-hydroxy-3-((2-phenylhydrazono)methyl)phenyl)diazenyl)phenyl) acetamide (2) was studied by DFT/B3LYP/6-311+G(d,p) basis set. The calculated values of geometric structural parameters, Fourier transform infrared spectral data, highest occupied molecular orbital and lowest unoccupied molecular orbital, natural bond orbital, nucleus-independent chemical shifts, Fukui function, polarizability, hyperpolarizability, and UV data of compounds 1 and 2 clearly indicate that substitution of the amino group alters the physical properties of compound 2. The nucleus-independent chemical shift values of the amino-substituted phenyl ring reduces the aromatic character due to the lone pair electron on nitrogen involved in inductive and conjunction effects, as well as due to OH, NH2 and OH, NHCOCH3 in compounds 1 and 2, respectively. The effect of the solvent on different parameters was studied, and it was found that increasing the dielectric constant increased the parameter studied. The stability and planarity of the molecule’s effects on dipole moment, energy, polarizability, and hyperpolarizability were studied extensively.

COF‐Topological Quantum Material Nano‐heterostructure for CO2 to Syngas Production under Visible Light

AbstractEfficient solar‐driven syngas production (CO+H2 mixture) from CO2 and H2O with a suitable photocatalyst and fundamental understanding of the reaction mechanism are the desired approach towards the carbon recycling process. Herein, we report the design and development of an unique COF‐topological quantum material nano‐heterostructure, COF@TI with a newly synthesized donor‐acceptor based COF and two dimensional (2D) nanosheets of strong topological insulator (TI), PbBi2Te4. The intrinsic robust metallic surfaces of the TI act as electron reservoir, minimising the fast electron‐hole recombination process, and the presence of 6s2 lone pairs in Pb2+ and Bi3+ in the TI helps for efficient CO2 binding, which are responsible for boosting overall catalytic activity. In variable ratio of acetonitrile‐water (MeCN : H2O) solvent mixture COF@TI produces syngas with different ratios of CO and H2. COF@TI nano‐heterostructure enables to produce higher amount of syngas with more controllable ratios of CO and H2 compared to pristine COF. The electron transfer route from COF to TI was realized from Kelvin probe force microscopy (KPFM) analysis, charge density difference calculation, excited state lifetime and photoelectrochemical measurements. Finally, a probable mechanistic pathway has been established after identifying the catalytic sites and reaction intermediates by in situ DRIFTS study and DFT calculation.

An insight into the structural, magnetic and dielectric properties of modified SrFe12-xPbxO19 (x = 0–0.3)

Effect of Pb2+ substitutions on the structural, magnetic and dielectric properties of SrFe12O19 in the form of SrFe12-xPbxO19 (x = 0, 0.1, 0.2 and 0.3) is carried out. All the samples crystalize in hexagonal magneto-plumbite structure with P63/mmc symmetry. An irregular but randomly distributed particles with average particle size increased from 0.791 μm to 1.131 μm due to substitutions. A characteristics Hopkinson peak is observed just below the transition temperature, may be stems from the superparamagnetic relaxations. The isothermal magnetization depicts an increase in coercivity (Hc) and decrease in saturation magnetization (Ms) due to Pb substitutions, which is further explained in the framework of site symmetry of the Fe and its multiple valence states. Mossbauer study reflects that, Fe3+/ Fe2+ present in the systems are associated with different electric environment. Furthermore, the shifting of dielectric transition by 50 °C upon substitutions is associated to dipole formation in presence of lone pair of Pb2+. A relaxor type of behavior is acquired by the system with a non-Debye type of relaxation is explained on the basis of complexity of the dipoles associated with each crystallographic sites.

Amine functionalized graphene oxide decorated with ZnO-WO3 nanocomposites for remediation of organic dye from wastewater

Photocatalytic degradation is as an efficient technique to eradicate toxic chemical pollutants from contaminated water sources. However, the selectivity and photocatalytic activity are the challenging targets to explore the new photocatalysts. Therefore, our research goal is to develop a suitable photocatalyst to satisfy the recent photocatalytic degradation demand. In this work, amine functionalized graphene oxide (NH2-GO) supported heterojunction ternary novel nanocomposites (NH2-GO/ZnO-WO3) were prepared via simple solvothermal method. Structural and morphological investigations of the prepared composites are systematically observed by Field Emission Scanning Electron Spectroscopy (FE-SEM), X-ray Diffraction (XRD), Fourier Transform Infrared Spectroscopy (FT-IR), and Ultraviolet–Visible (UV–vis) Spectroscopy. FT-IR analysis confirmed the effective functionalization of amine on graphene oxide. The XRD results indicated that the prepared nanocomposites were free from any impurities and the binary composite (NH2-GO/ZnO) showed hexagonal wurtzite structure, whereas the ternary composite (NH2-GO/ZnO-WO3) exhibited mix crystal structure of monoclinic and hexagonal phase of WO3 and ZnO, respectively. The synthesized ternary photocatalyst (NH2-GO/ZnO-WO3) demonstrated superior photocatalytic efficiency towards various organic dyes such as cationic dye methylene blue (MB, 85.89%) and anionic dye methyl orange (MO, 60.98%) compared to binary photocatalyst (NH2-GO/ZnO) that showed only 52.28% of MB and 25.8% of MO dye degradation under UV light irradiation. The enhanced photocatalytic performance was mainly due to the low recombination rate of photogenerated electron-hole pair, narrow band gap, and large surface area of ternary composite. The presence of lone pair electrons in amino group provides a negative-charged surface composite resulting good interaction with cationic dye is the key to upgrade the photocatalytic performance. The ternary nanocomposite NH2-GO/ZnO-WO3 has the capacity to be a competent and acceptable photocatalyst for the photodegradation of organic dyes used in industries.

Real Structure, Magnetism and Chemical Bonding of SmSi3‐x

New metastable SmSi3‐x (x = 0‐0.05) is obtained by high‐pressure high‐temperature synthesis (9.5 GPa, 870‐1270 K). Powder diffraction data refinements reveal that the crystal structure of SmSi3 is isotypic to that of YbSi3 (space group I4/mmm, a = 7.23634(5) Å, c = 11.0854(1) Å). In the crystal structure, two types of Si2 dumbbells agglomerate into layers, which embed the samarium atoms. At ambient pressure, SmSi3 decomposes exothermally upon heating into Si and SmSi2‐x. Single‐crystal structure refinements of a specimen SmSi3‐x (x=0.05) reveal considerable electron density, which is not accounted for by the YbSi3 model. The additional maxima can be assigned to disorder which affects the samarium positions and induces silicon vacancies. Scanning transmission electron microscopy experiments evidence that the disorder can be attributed to extended defects. Magnetic measurements on SmSi3‐x reveal van Vleck paramagnetic behavior and antiferromagnetic ordering at low temperatures. Computations within the local spin density approximation (LSDA and LSDA+U) on the crystal structure of SmSi3 reproduce the anti­ferro­magnetic coupling as the favored long‐range order. Quantum chemical analysis of the chemical bonding in SmSi3 reveals two‐center two‐electron bonds within the Si2 dumbbells plus a total of a little less than four electrons in lone pairs at each silicon atom.

Synthesis, crystal structure, Hirshfeld surface analysis, spectral characterisation, non-covalent interactions and anti-microbial investigation on morpholinium adipate: a combined experimental and DFT approach

MPAA was synthesised and evaluated using spectroscopic methods and quantum chemical computations in the proposed investigation. Extensive quantum chemical computations were employed to analyse FT-IR, FT-Raman and NMR spectra of molecule morpholinium adipate (MPAA). The results of a single crystal X-ray diffraction (SCXRD) experiment were compared with estimated structural characteristics. In conjunction with the scaled force constants, a comprehensive vibrational assignment is provided for the 96 anticipated vibration modes of MPAA. Charge transport inside the molecule is exposed by the band gap energy of 5.959 eV, which is the consequence of the predicted Highest Occupied Molecular Orbital (HOMO) and Lowest Unoccupied Molecular Orbital (LUMO) values of −6.991 and −1.031 eV, respectively. The inter- and intramolecular H-bonding contacts in the molecule were studied using natural bond orbital analysis to learn more about the biological active site. The eventual charge transfer inside the molecule is supported by frontier molecular orbital analysis and natural bond orbital analysis. The anti-bonding of H15–O24 atoms and the lone pair N14 had the greatest stabilising energy at 16.52 kcal/mol. Using Hirshfeld surface analysis methods, intermolecular connections and crystal packing of MPAA are investigated. The fukui and electrostatic potential plot analyses can provide information about the molecule’s electrophilic and nucleophilic locations. Antimicrobial tests have been performed to see how well the chemical worked against various bacterial and fungal strains. Docking of 8OEO (Aspergillus Niger), 7C2O (Candida parapsilosis), 2O6I (Enterococcus faecalis) and 1DZO (Pseudomonas aeruginosa) proteins has been done, and lowest binding energy −4.57 kcal/mol has been achieved for 7C2O protein.

Synthesis, Resolution, and Absolute Configuration of a Phosphine-Based Hemicryptophane Cage with an Endo Phosphorus Lone Pair and Formation of the Corresponding Gold Complex.

The synthesis, characterization, and chiroptical properties of a new class of hemicryptophanes combining a phosphine moiety and a cyclotriveratrylene unit are reported. The synthesis was short and efficient. The racemic mixture of the cage was resolved by chiral high-performance liquid chromatography (HPLC), giving access to enantiopure molecular cages, whose absolute configurations could be assigned by electronic circular dichroism (ECD) spectroscopy. These new phosphines were then reacted with gold in order to make the corresponding enantiopure gold complexes. The X-ray structure reveals an endohedral functionalization of the cage with the gold metal entrapped in the heart of the cavity, leading to a Vbur of 58%. Moreover, the chirality of the cyclotriveratrylene unit was found to control the chiral arrangement of the aryl group linked to the phosphorus atom, located at the opposite side of the cavity.

Rearrangement of Arylsulfamates and Sulfates to Para-Sulfonyl Anilines and Phenols.

The C(sp2)-aryl sulfonate functional group is found in bioactive molecules, but their synthesis can involve extreme temperatures (>190 °C or flash vacuum pyrolysis) and strongly acidic reaction conditions. Inspired by the 1917 Tyrer industrial process for a sulfa dye that involved an aniline N(sp2)-SO3 intermediate en route to a C(sp2)-SO3 rearranged product, we investigated tributylsulfoammonium betaine (TBSAB) as a milder N-sulfamation to C-sulfonate relay reagent. Initial investigations of a stepwise route involving TBSAB on selected anilines at room temperature enabled the isolation of N(sp2)-sulfamate. Subsequent thermal rearrangement demonstrated the intermediary of a sulfamate en route to the sulfonate; however, it was low-yielding. Investigation of the N-sulfamate to C--sulfonate mechanism through control experiments with variation at the heteroatom positions and kinetic isotope experiments (KIEH/D) confirmed the formation of a key N(sp2)-SO3 intermediate and further confirmed an intermolecular mechanism. Furthermore, compounds without an accessible nitrogen (or oxygen) lone pair did not undergo sulfamation- (or sulfation) -to-sulfonation under these conditions. A one-pot sulfamation and thermal sulfonation reaction was ultimately developed and explored on a range of aniline and heterocyclic scaffolds with high conversions, including N(sp2)-sulfamates (O(sp2)-sulfates) and C(sp2)-sulfonates, in up to 99 and 80% (and 88% for a phenolic example) isolated yield, respectively. Encouragingly, the ability to modulate the ortho-para selectivity of the products obtained was observed under thermal control. A sulfonated analog of the intravenous anesthetic propofol was isolated (88% yield), demonstrating a proof-of-concept modification of a licensed drug alongside a range of nitrogen- and sulfur-containing heterocyclic fragments used in drug discovery.

Origin of low lattice thermal conductivity in promising ternary PbmBi2S3+m (m = 1–10) thermoelectric materials

Ternary Pb-Bi-S compounds emerge as potential thermoelectric materials owing to low thermal conductivity, but the origin of their intrinsic low lattice thermal conductivities lacks further investigation. Herein, a series of ternary PbmBi2S3+m (m = 1–10) compounds are synthesized and their crystal structure evolutions with increasing m values are clearly unclosed. The room-temperature lattice thermal conductivities in PbBi2S4, Pb3Bi2S6 and Pb6Bi2S9 can reach at 0.57, 0.56 and 0.80 W m−1 K−1, respectively, outperforming other ternary sulfur-based compounds. Theoretical calculations show that the low lattice thermal conductivities in PbmBi2S3+m (m = 1–10) mainly originate from soft phonon dispersion caused by strong lattice anharmonicity, and both asymmetric chemical bond and lone pair electrons (Pb 6s2 and Bi 6s2) can favorably block phonon propagation. Furthermore, the elastic measurements also confirm relatively low sound velocities and shear modulus, and the Grüneisen parameter (γ) calculated by sound velocities can reach at 1.67, 1.85 and 1.94 in PbBi2S4, Pb3Bi2S6 and Pb6Bi2S9, respectively. Finally, the intrinsic low lattice thermal conductivities in PbmBi2S3+m (m = 1–10) contribute to promising thermoelectric performance, and the maximum ZT values of 0.47, 0.38 and 0.45 can be achieved in undoped PbBi2S4, Pb3Bi2S6 and Pb6Bi2S9, respectively.