Dispersion-corrected Density Functional Theory Research Articles

Enhanced water molecule sensitivity on defective WS2 monolayers through (ZnO)12 spherical nanocages decoration: A theoretical study

The adsorption of water molecules on sulfur vacancies (VS and V2S2) and gold atoms embedded in the sulfur vacancies (AuS) of tungsten disulfide (WS2) monolayers (ML) decorated with zinc-oxide (ZnO)12 nanocages were studied using dispersion-corrected density functional theory. Since the WS2 monolayer is predominantly inert, the introduction of defect states into the mid-bandgap region is significant due to its chemical and physical implications. The possibility of turning from an electron acceptor (p-type) to an electron donor (n-type) semiconductor character, when the sulfur vacancy density is varied or if the sulfur vacancies are filled with gold atoms, was demonstrated. The binding energy of the Au atom forming the AuS defect and the diffusion energy barrier from the VS defect to an adjacent site for Au were determined as 2.99 and 2.16 eV, respectively. Consequently, the substitutional defect AuS remains attached to the ML. The adsorption energy showed that the water molecule is chemisorbed on AuS defect on WS2 (n-type). Also, the density of states suggests a clear response as the chemiresistive sensor. Besides, how zinc-oxide spherical nanocages behave as sensors for different relative humidity levels was discussed. The response to water molecules was significantly enhanced by the chemisorption of the (ZnO)12 spherical nanocage on WS2-AuS. These composed systems formed WS2-ZnO heterojunctions with differences in the electronic structure. The study provides a comprehensive outlook on analyte interactions with WS2 (n-type) and WS2-ZnO surfaces, which have been utilized in the design of semiconductor gas sensors.

Two-Dimensional TiS2 Nanosheet- and Conjugated Polymer Nanoparticle-Based Composites for Sensing Applications.

The assessment of phenolic compounds in food samples, environmental samples, and medical applications has gained importance recently. Here, we present research on novel conjugated polymer nanoparticles (P-PimBzBt NPs) and their composites with two-dimensional titanium disulfide nanosheets (2D-TiS2) for electrochemical tyrosinase (TYR)-based catechol detection. P-PimBzBt NPs are decorated with 2D-TiS2 to enhance the electrochemical performance for biosensing. In addition, the interaction of P-PimBzBt NPs with TiS2 was investigated at the molecular level by employing van der Waals (vdW) dispersion-corrected density functional theory (DFT) calculations and classical all-atom molecular dynamics simulations. According to the theoretical studies, the presence of the TiS2 layer increases the interfacial interaction with the conjugated polymer via electrostatic interactions. Using cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS), field emission scanning electron microscopy (FE-SEM), and energy-dispersive X-ray spectroscopy (EDS) analyses, the production of SPE/TiS2@P-PimBzBt NPs/TYR nanobiosensors was examined. With a detection range of 3.0-27.5 μM, 0.33 μM LOD, and 3.89 μA/μM·cm2 sensitivity values, the sensing layer based on the TiS2@P-PimBzBt NP composites has a targeting ability toward catechol. Its selectivity was investigated using commonly used interfering ions and compounds such as citric acid, urea, glucose, uric acid, KCl, and NaCl. Application of nanobiosensors to actual samples (tap water and black tea) was carried out with high accuracy. The fabricated biosensing platform demonstrates that P-PimBzBt NPs with 2D-TiS2 nanomaterial functionalization are appropriate as electrode materials and could be used to create an inexpensive, fast-response, and highly selective electrochemical biosensor for the detection of catechol in actual samples.

Low-temperature oxidation of methane mediated by Al-doped ZnO cluster and nanowire: a first-principles investigation.

First-principles calculations are performed to investigate the catalytic oxidation of methane by using N2O as an oxidizing agent over aluminum (Al)-doped Zn12O12 cluster and (Zn12O12)2 nanowire. The impact of Al impurity on the geometry, electronic structure, and surface reactivity of Zn12O12 and (Zn12O12)2 is thoroughly studied. Our study demonstrates that Al-doped ZnO systems have a better adsorption ability than the corresponding pristine counterparts. It is found that N2O molecule is initially decomposed on the Al site to provide the N2 molecule, and an Al-O intermediate which is an active species for the CH4 oxidation. The conversion of CH4 into CH3OH over AlZn11O12 and (AlZn11O12)2 requires an activation energy of 0.45 and 0.29eV, respectively, indicating it can be easily performed at normal temperatures. Besides, the overoxidation of methanol into formaldehyde cannot take place over the AlZn11O12 and (AlZn11O12)2, due to the high energy barrier needed to dissociate C-H bond of the CH3O intermediate. Dispersion-corrected density functional theory calculations were performed through GGA-PBE exchange-correlation functional combined with a numerical double-ζ plus polarization (DNP) basis set as implemented in DMol3. To include the relativistic effects of core electrons of Zn atoms, DFT-semicore pseudopotentials were adopted. The DFT + D scheme proposed by Grimme was used to involve weak dispersion interactions within the DFT calculations. The reaction energy paths were generated by the minimum energy path calculations using the NEB method.

Development of new sustainable pyridinium ionic liquids: From reactivity studies to mechanism-based activity predictions.

This study addresses the development of sustainable pyridinium ionic liquids (ILs) because of their potential applications in agriculture and pharmaceuticals. Pyridinium-based ILs are known for their low melting points, high thermal stability, and moderate solvation properties. We synthesized three novel pyridinium-based ILs: 1-(2-(isopentyloxy)-2-oxoethyl)pyridin-1-ium chloride, 1-(2-(hexyloxy)-2-oxoethyl)pyridin-1-ium chloride, and 1-(2-(benzyloxy)-2-oxoethyl)pyridin-1-ium chloride. The biological activities of these compounds were evaluated through plant growth promotion, herbicidal, and insecticidal assays. Our results show that the benzyloxy derivative significantly enhances wheat and cucumber growth, whereas the isopentyloxy compound has potent herbicidal effects. Computational methods, including DFT calculations and molecular docking, were applied to understand the structure‒activity relationships (SARs) and mechanisms of action. The computational techniques involved dispersion-corrected density functional theory (DFT) with the B3LYP functional and the 6-311G** basis set. Grimme's D3 corrections were included to account for dispersion interactions. The calculations were performed via GAMESS-US software. Quantum descriptors of reactivity, such as ionization potential, electron affinity, chemical potential, and electrophilicity index, were derived from the HOMO and LUMO energies. Molecular docking studies were conducted via the CB-Dock server via AutoDock Vina software to predict binding affinities to cancer-related proteins. Petra/Osiris/Molinspiration (POM) analysis was used to predict the drug likeness and other pharmaceutical properties of the synthesized ILs.

A polyhedron-based metal-organic framework with electronegative donor sites for efficient C2H6/C2H4 separation

Ethylene is an important chemical raw material which is widely used in the production of chemical fibers, plastics, rubber, coatings, as well as medicines, and its separation from the gas mixtures of C2H6/C2H4 is of great importance but a challenging task due to their similar physical properties and molecular dimensions. Herein, we report the C2H6 and C2H4 sorption studies on a robust anionic metal-organic framework (MOF) {(NH2Me2)[Co3(μ3OH)(TPT)(TZB)3](H2O)6(DMA)6}n (Co-MOF) formed by connection of Co3(OH) clusters by two N-rich organic ligands 2,4,6-tri(4-pyridyl)-1,3,5-triazine (TPT) and 4-(1H-Tetrazol-5-yl)benzoic acid (H2TZB). The prepared Co-MOF features a polyhedron stacking network structure composed of trigonal bipyramidal cages and octahedral cage which both contribute to a high C2H6 uptake capacity of 6.48 mmol/g and a decent C2H6/C2H4 selectivity of 1.54 at 298 K and 1 bar. Grand Canonical Monte Carlo (GCMC) simulation results agree well with the experimental tendency, both in the adsorption isotherms and sorption heats, which demonstrated that the suitable pore surfaces with electronegative donor sites generated multiple CH ⋅⋅⋅O/N and CH ⋅⋅⋅π interactions between the framework and C2H6, resulting in a stronger interaction between the MOF skeleton and C2H6 molecule than C2H4 as reflected by the dispersion-corrected density functional theory (DFT) calculation.

High-throughput screening of efficient graphdiyne supported transition metal single atom toward water electrolysis and oxygen reduction

Efficient single-atom electrocatalysts show great potential for application in the field of renewable energy. In this work, dispersion-corrected density functional theory (DFT) calculations based on high-throughput screening were used to identify effective graphdiyne (GDY) supported single-atom electrocatalysts (SAECs) for water electrolysis and the oxygen reduction reaction (ORR). The solvation effect on the electrocatalytic performance of the catalysts was carefully discussed. A general design principle was established to evaluate the activities of TM@GDY SAECs for ORR and oxygen evolution reaction (OER). ΔGOH* could serve as the sole descriptor for the onset potential of OER and ORR. Additionally, a universal structural descriptor φ, which is strongly related to ΔGOH*, was identified. This descriptor only includes intrinsic features such as the number of electrons in d orbitals and elemental electronegativity. Consequently, a structure-activity volcano was plotted. Combined with the electronic properties calculations, the mechanism behind the relationship between ΔGOH* and descriptor φ was deeply analyzed. Among the investigated candidates, TM@GDY (TM = Ni, Pt, Pd, Cu, Co, Rh, and Ag) are potential bifunctional electrocatalysts for OER and ORR. Three non-noble metal-based SAECs (Ni@GDY, Co@GDY, and Cu@GDY) and two noble metal-based SAECs (Rh@GDY and Ag@GDY) are potential trifunctional electrocatalysts for OER, ORR, and the hydrogen evolution reaction.

Highly-selective Electrocatalytic Reduction of NO to NH3 using Cu Embedded WS2 Monolayer as Single-atom Catalyst: A DFT Study.

Electrocatalytic nitric oxide reduction reaction (NORR) is a promising method for generating NH3. However, developing a NORR catalyst for NH3 synthesis with low cost and high efficiency is still challenging. We here report a series of single-atom catalysts (SACs), designed by embedding nine different transition metals from Sc to Cu in S-vacant WS2 monolayer (TM@WS2), and investigate the electrocatalytic performance for NORR process using the dispersion-corrected density functional theory (DFT) calculations. Among them, Cu-based SACshows a strong binding to the WS2 surface and high selectivity towards NORR process, and also it greatly inhibits the competing hydrogen evolution reaction (HER). Through ab initio molecular dynamics (AIMD) simulations, the thermal stability of SAC is assessed and found no structure deformation even at 500 K temperature. All possible reactive pathways including distal and alternating mode at both N- and O-end configurations for NH3 production were explored. We predicted that the Cu@WS2 SAC exhibits remarkable catalytic activity and selectivity with lowest limiting potential of -0.41 V via the N-alternating pathway. Our study emphasize that the transition metal dichalcogenide (TMDC) based SACs are potential candidates for converting NO to NH3, and this opens a new avenue in designing NORR catalysts with high catalytic performance.

Enabling Visible Light Sensitization of YbIII, NdIII and ErIII in Dimeric LnIII/GaIII Metallacrowns through Functionalization with RuII Complexes for NIR-II Multiplex Imaging.

Multiplex imaging in the second near-infrared window (NIR-II, 1000-1700 nm) provides exciting opportunities for more precise understanding of biological processes and more accurate diagnosis of diseases by enabling real-time acquisition of images with improved contrast and spatial resolution in deeper tissues. Today, the number of imaging agents suitable for this modality remains very scarce. In this work, we have synthesized and fully characterized, including theoretical calculations, a series of dimeric LnIII/GaIII metallacrowns bearing RuII polypyridyl complexes, LnRu-3 (Ln = YIII, YbIII, NdIII, ErIII). Relaxed structures of YRu-3 in the ground and the excited electronic states have been calculated using dispersion-corrected density functional theory methods. Detailed photophysical studies of LnRu-3 have demonstrated that characteristic emission signals of YbIII, NdIII and ErIII in the NIR-II range can be sensitized upon excitation in the visible range through RuII-centered metal-to-ligand charge transfer (MLCT) states. We have also showed that these NIR-II signals are unambiguously detected in an imaging experiment using capillaries and biological tissue-mimicking phantoms. This work opens unprecedented perspectives for NIR-II multiplex imaging using LnIII-based molecular compounds.

Computational analysis of bare and alkali metal-encapsulated Al12N12 nanocages for enhanced removal of fluoroquinolone antibiotics from wastewater

Antibiotics, particularly fluoroquinolones, and their residues pose significant risks to both aquatic and human life, underscoring the need for effective removal strategies. While nanomaterials show promise in addressing this issue, the theoretical understanding of their interactions with antibiotics has been limited. In this context, we conducted DFT calculations to explore the interactions between fluoroquinolone antibiotics and the Al12N12 nanocage, aiming to provide valuable data for future experimental investigations. In the present research, the adsorption behavior of fluoroquinolone (FQ) antibiotics including ciprofloxacin (C17H18FN3O3), gemifloxacin (C18H20FN5O4), levofloxacin (C18H20FN3O4), moxifloxacin (C21H24FN3O4), delafloxacin (C18H12ClF3N4O4) and ofloxacin (C18H20FN3O4) onto the surface of the bare and metal-encapsulated Al12N12 (Li-Al12N12 and Na-Al12N12) nanocages are studied using dispersion corrected density functional theory (DFT-D) calculations. The primary purpose is to explore the potential application of these nanomaterials for efficient fluoroquinolone removal. The results indicate that the encapsulation of Li or Na inside Al12N12 nanocage enhances the adsorption of the FQs. The desorption process is also investigated in acidic medium, revealing that Li-Al12N12 and Na-Al12N12 cages emerge as superior candidate than the bare Al12N12 nanocage for controlled FQs removal applications. The Li-Al12N12 and Na-Al12N12 are introduced as promising candidates for fluoroquinolone removal in aqueous medium. This study might provide an innovative perspective for future investigations in the field of the drug pollution removal using aluminum nitride-based nanomaterials.

Hydroxyl radical-induced C1'-H abstraction reaction of different artificial nucleotides.

Recently, a few antiviral drugs viz Molnupiravir (EIDD-1931), Favipiravir, Ribavirin, Sofosbuvir, Galidesivir, and Remdesivir are shown to be beneficial against COVID-19 disease. These drugs bind to the viral RNA single strand to inhibit the virus genome replication. Similarly, recently, some artificial nucleotides, such as P, J, B, X, Z, V, S, and K were proposed to behave as potent antiviral candidates. However, their activity in the presence of the most reactive hydroxyl (OH) radical is not yet known. Here, the possibility of RNA strand break due to the OH radical-induced C1'-hydrogen (H) abstraction reaction of the above molecules (except Remdesivir) is studied in detail by considering their nucleotide conformation. The results are compared with those of the natural RNA nucleotides (G, C, A, and U). Due to low Gibbs barrier-free energy and high exothermicity,all these nucleotides (except Remdesivir) are prone to OH radical-inducedC1'-H abstraction reaction.As Remdesivir contains a C1'-CN bond,the OH radical substitution reactions at theCN and C1' siteswould likely liberate the catalytically important CN group, thereby downgrading its activity. Initially, the B3LYP-D3 dispersion-corrected density functional theory method and 6-31 + G* basis set were used to optimize all reactant, transition state, and product complexes in the implicit aqueous medium. Subsequently, the structures of these complexes were further optimized by using the ωB97X-D dispersion-corrected density functional theory method and cc-PVTZ basis set in the aqueous medium. The IEFPCM method was used to model the aqueous medium.

Mechanism of ammonium adsorption onto the surface of heteroatom doped graphene quantum dots

The adsorption mechanism of ammonium (NH4+) ion onto graphene quantum dots (GQDs) surface, modified with vacancy and heteroatom (nitrogen (N) and oxygen (O)), has been studied using a combination of dispersion-corrected density functional theory (DFT) and quantum theory of atoms in molecules (QTAIM) approaches in aqueous media. The potential of GQD-NX and GQD-OX surfaces as highly effective adsorbents for NH4+ ions has been explored by detailed analysis of adsorption energies, molecular electrostatic potential, charge transfer, density-of-states, non-covalent interaction, and desorption time. It has been observed that the adsorption of NH4+ ions on the GQD-NX surfaces is primarily chemisorption, governed by electrostatic interactions and hydrogen bonds. However, adsorption of NH4+ over the surface of GQD-OX predominantly ranges from strong physisorption to weak chemisorption arising from van der Waals interactions and hydrogen bonds. These findings present compelling new approach utilizing modified GQDs as highly efficient adsorbents for removing NH4+ ions from water.

Density functional theory study of physisorption of ionic liquid pairs on hydroxylated and oxygen terminated α-SiO2 (001) surfaces

In this work, we investigate the ion pair tetramethylphosphonium cation, [P1,1,1,1]+, and bis(oxalato)borate anion, [BOB]−, as a model system for the study of ionic liquids interacting with both hydroxylated and oxygen terminated α-SiO2 (001) surfaces, using first-principles electronic structure theory. We use a single ionic pair and clusters of ion pairs, in order to have exclusively neutral supercell slab models. We use dispersion-corrected density functional theory (DFT) to ascertain that both the strong physical binding between the ions, dominated by ionic binding, and the weaker physical binding of ions to the different surfaces are correctly described. We have found that the binding of ion pairs is stronger to the hydroxylated α-SiO2 (001) surface compared to the oxygen terminated surface, which is attributed to the formation of H-binding with the oxygen atom(s) of the [BOB]− anion. Through rotation of ionic pair(s), we estimate the surface-ions energy barrier for translational movement and, thus, the strength of H-binding of the ions. At the surface of hydroxylated α-SiO2 (001), we have studied how water molecules form a network of H-binding with the OH groups of the surface and the [BOB]− anion, which offers an explanation for the reduction in the friction of ionic liquids on the inclusion of water. We suggest modeling protocols for simulation of ion pairs on surfaces, which can open up the possibility to use DFT to aid in designing and understanding the physicochemical mechanism of interactions of ionic materials (including ionic liquids) in various technological applications.

First principles insights into triboelectrification during solid-solid contact: The curious case of 2D MXenes and aluminum

Recently, triboelectric nanogenerators (TENGs) have been widely used for energy harvesting and self-powered sensing due to their significant and unique advantages. However, the intrinsic mechanisms that contribute to tribo-electricification (TE) between two materials remain as a subject of rigorous debate. In addition to predicting the qualitative charge transfer in solid-solid contacts based on the difference in the work functions of the two moieties constituting the interface, we argue that it is essential to obtain atomic-level, first principles, insights into the bonding properties, quantitative charge transfer, and the possible presence of a electrostatic potential barrier at the interface to fully understand the TE mechanism of a system. We have utilized dispersion-corrected density functional theory (DFT) calculations in this study to systematically investigate the TE potential of bare surface Ti3C2 and Ti3N2 2D MXene monolayers and their surface functionalized modifications Ti3C2R2 and Ti3N2R2 (where R = -O, -OH, or -F) in contact with Al(111). For these heterostructures, we have analyzed the adhesive energy of the interfaces, the nature of interaction through the electron localization function (ELF), and the charge distribution, which have revealed distinct characteristics of MXene/Al contacts for these monolayer/metal interfaces at their equilibrium distance and the changes in their properties under uniaxial pressure. Among all the metallic 2D MXene variants investigated in this study, we have determined that Ti3C2F2/Al and Ti3N2F2/Al interfaces show exceptional potential for TE.

Quantum chemical insights into the adsorption performance of pristine and M-encapsulated (M = Li, Na, K) B12N12 nanocages toward ciprofloxacin, levofloxacin, moxifloxacin, delafloxacin and ofloxacin antibiotics

The adsorption behavior of fluoroquinolone (FQ) antibiotics, including ciprofloxacin (C17H18FN3O3), levofloxacin (C18H20FN3O4), moxifloxacin (C21H24FN3O4), delafloxacin (C18H12ClF3N4O4) and ofloxacin (C18H20FN3O4) onto the surface of pristine and M-encapsulated B12N12 (M = Li, Na and K) nanocages are studied using dispersion corrected density functional theory (DFTD) calculations. The potential use of these nanomaterials for effective removal of FQ was systematically investigated in this study. Metal-encapsulated cages exhibit higher adsorption energies, making them favorable candidates for the removal of FQs from water. Results reveal that the desorption mechanism facilitated the efficient release of FQ from Li-B12N12 and Na-B12N12 nanocages in acidic medium. The outcomes provide a novel insight for future research on the adsorption mechanisms of pharmaceuticals on boron nitride-based nanomaterials.

Adsorption and diffusion behavior of lithium atom on boron-doped armchair graphene nanoribbon- A dispersion-corrected DFT study

In this paper, we study the relevance of considering dispersion interactions in DFT calculations to determine the adsorption behavior of lithium atom(s) on boron-doped armchair graphene nanoribbons. Our findings suggest that substitutional doping with boron atoms makes the AGNR electron-deficient which results in charge transfer from Li to the AGNR. Li atom binds more strongly to B-doped AGNR than pristine AGNR. A stronger Li-C interaction prevents the clustering of Li atoms, thus, inhibiting dendrite growth. The maximum storage capacity of B-doped AGNR reaches to 1261 mAh/g. B-doped AGNR offers a lower diffusion barrier of 0.19 eV to Li atom as compared to pristine AGNR. From the analysis of density of states, it is observed that the semiconducting nature of both pristine and B-doped AGNRs turns into metallic after the adsorption of lithium atom. Our results show that B-doped AGNR can be used as a potential anode material of lithium-ion batteries.

Probing Self-Assembly of Ammeline in Chloroform and Aqueous Media: Interplay Between Hydrogen Bonding Diversity and Dimerization.

Ammeline (AM) is a molecule with a very low reputation in the field of supramolecular community, but with a recently proven potential both experimentally and theoretically. In this work, dispersion-corrected density functional theory (DFT-D) computations and molecular dynamics (MD) simulations were employed to understand the aggregation mechanism of AM in chloroform and water media. Our DFT-D and MD analyzes show that the most important interactions are those formed by the amine groups (-NH2) with both the pyridine-type nitrogen atoms and the carbonyl groups (C=O). In the more polar solvent, the interactions between water molecules and the C=O group prevent the AM from forming more interactions with itself. Nevertheless, four types of dimers involving N-H∙∙∙O interactions were found to exist in water solutions. The overlooked tetrel bond between endocyclic N and C atoms can also stabilize dimers in solution. Moreover, while most AM dimers are enthalpy-driven, our results indicate that the unique DD-AA dimer (D=donor, A=acceptor) that originates cyclic rosettes is entropy-driven.

Constructing local nanomolecular trap in a scalable, low-cost, and ultramicroporous metal–organic framework for efficient capture of greenhouse gases SF6 and CO2

The capture of sulfur hexafluoride (SF6) and carbon dioxide (CO2) is an important but challenging task for reducing greenhouse gas emission and thereby diminishing negative impacts of global climate change. Herein, we integrated local nanomolecular traps into an inexpensive cobalt-based metal–organic framework (MOF, namely GNU-3) with suitable pore sizes and functional pore surfaces for capturing greenhouse gases. Activated GNU-3a showed good adsorption and separation properties for SF6 and CO2. Especially for SF6, GNU-3a displayed the high SF6/N2 (10:90, v/v) selectivity of 317.6 and SF6 uptake capacity of 2.63mmol/g at 298 K and 1.0 bar. Grand canonical Monte Carlo simulations and first-principles dispersion-corrected density functional theory calculations identified that gas molecules were favorably trapped in polyaromatic ring functionalized channel centers and nanomolecular traps of pore walls by the strong hydrogen bond interactions. Excellent breakthrough results recommend practical separating properties of GNU-3a for binary SF6/N2 and CO2/N2 mixtures, and ternary SF6/CO2/N2 mixtures. Moreover, benefitting from superior features of cheap raw materials and large-scale synthesis, GNU-3 is expected to be applied to practical industrial scenarios. This work may provide insights into constructing prospectively industrial porous MOF adsorbents with optimal pore structures for greenhouse gas capture.

Density Functional Theory Calculations for Interpretation of Infra-Red Spectra of Liquid Crystalline Chiral Compound

The experimental IR spectra of (S)-4′-(1-methylheptyloxycarbonyl) biphenyl-4-yl 4-[2-(2,2,3,3,4,4,4-heptafluorobutoxy) ethyl-1-oxy]-2-fluorobenzoate in the crystal phase are analyzed with the help of dispersion-corrected density functional theory (DFT+D3) calculations for isolated molecular monomer and dimer models, and a periodic model computed at the extended density functional tight-binding (xTB) level of theory. It is found that the frequency scaling coefficients obtained with the results of the molecular calculations are good matches for the crystal phase, being close to 1. The molecular and periodic models both confirm that varied intra- and intermolecular interactions are crucial in order to reproduce the broadened shape of the experimental band related to C=O stretching; the key factors are the conjugation of the ester groups with the aromatic rings and the varied intermolecular chemical environments, wherein the C=O group that bridges the biphenyl and F-substituted phenyl groups seems particularly sensitive. The C=O stretching vibrations are investigated as a function of temperature, covering the range of the crystal, smectic CA*, smectic C* and isotropic liquid phases. The structure changes are followed based on the X-ray diffraction patterns collected in the same temperatures as the IR spectra. The experimental and computational results taken together indicate that the amount of weak C=O…H-C hydrogen bonds between the molecules in the smectic layers decreases with increasing temperature.

Photocascade chemoselective controlling of ambident thio(seleno)cyanates with alkenes via catalyst modulation

Controlling the ambident reactivity of thiocyanates in reaction manifolds has been a long-standing and formidable challenge. We report herein a photoredox strategy for installing thiocyanates and isothiocyanates in a controlled chemoselective fashion by manipulating the ambident-SCN through catalyst modulation. The methodology allows redox-, and pot-economical ‘on-demand’ direct access to both hydrothiophene and pyrrolidine heterocycles from the same feedstock alkenes and bifunctional thiocyanomalonates in a photocascade sequence. Its excellent chemoselectivity profile was further expanded to access Se- and N-heterocycles by harnessing selenonitriles. Redox capability of the catalysts, which dictates the substrates to participate in a single or cascade catalytic cycle, was proposed as the key to the present chemodivergency of this process. In addition, detailed mechanistic insights are provided by a conjugation of extensive control experiments and dispersion-corrected density functional theory (DFT) calculations.

Revisiting the structure of [PdAu9(PPh3)8(CN)]2+ produced by atmospheric pressure plasma irradiation of [PdAu8(PPh3)8]2+ in methanol.

Some of the authors of the present research group have previously reported mass spectrometric detection of [PdAu9(PPh3)8(CN)]2+ (PdAu9CN) by atmospheric pressure plasma (APP) irradiation of [MAu8(PPh3)8]2+ (PdAu8) in methanol and proposed based on density functional theory (DFT) calculations that PdAu9CN is constructed by inserting a CNAu or NCAu unit into the Au-PPh3 bond of PdAu8 [Emori et al., J. Chem. Phys. 155, 124312 (2021)]. In this follow-up study, we revisited the structure of PdAu9CN by high-resolution ion mobility spectrometry on an isolated sample of PdAu9CN with the help of dispersion-corrected DFT calculation. In contradiction to the previous proposal, we conclude that isomers in which an AuCN unit is directly bonded to the central Pd atom of PdAu8 are better candidates. This assignment was supported by Fourier transform infrared and ultraviolet-visible spectroscopies of isolated PdAu9CN. The simultaneous formation of [Au(PPh3)2]+ and PdAu9CN suggests that the AuCN species are formed by APP irradiation at the expense of a portion of PdAu8. These results indicate that APP may offer a unique method for transforming metal clusters into novel ones by generating in situ active species that were not originally added to the solution.