Basis Set Research Articles

ExoMol line lists – LIX. High-temperature line list for N2O

Abstract New hot line lists for five isotopologues of N2O are presented, for the parent 14N216O and 4 singly substituted species 14N217O, 14N218O, 14N15N16O and 15N14N16O. The line lists have been computed with the variational program TROVE using a new empirical potential energy surface (PES) and an accurate ab initio dipole moment surface of N2O Ames-1. The PES was obtained by fitting to experimentally derived energies of N2O compiled using the well established MARVEL procedure. Here we also introduce an ‘artificial symmetry group’ Cns(AEM) for an efficient construction of rotation-vibrational basis set of a linear non-symmetric triatomic molecule of the XYZ type. The line lists cover the rotational excitations up to J = 160 and the wavenumber range up to 20000 cm−1. MARVEL energies are also used to improve predicted line positions resulting in excellent agreement with the available experimental spectra, as demonstrated. An extensive comparison with existing line lists for N2O HITRAN, HITEMP, NOSL-296, NOSD-1000 and Ames-296K is provided. The line lists are freely accessible from www.exomol.com.

Synthesis, spectral characterization, anti-cancer activity evaluation, and molecular docking of substituted 1,2-bis(3-butyl-2,6-diphenylpiperidin-4-ylidiene)hydrazone derivatives

A series of 1,2-bis(3‑butyl‑2,6-diphenylpiperidin-4-ylidiene)hydrazone derivatives of the substituted compounds 1–7, were confirmed by the characterization of IR & 1H-, NMR spectrum, together with X-ray crystallography and Mass spectroscopy also incredibly revealed. Docking analysis of the synthesized compounds employed under the protein from PDB code as 5cqh1, 4i40, 5fan, 7nud, 6Ya1 offers more inhibition values from 2D and 3D structures of the compounds, followed by Anti-cancer activity of the carcinoma cell line displayed that, highly potent to be active in nature. The in-vitro performance of -Cl substituted compound 6 (high anticancer activity) was in good correlation with its protein binding behaviour (strong binding). The increasing order of anticancer effect was 5>7>1>2>4>3>6 and the increasing order of binding ability on proteins were 7>3>4>1>2>5>6. The computational investigations were aligned with experimental techniques using Density Functional Theory (DFT) with a 6–31 G (d, p) basis set. Calculated Highest Occupied Molecular Orbital (HOMO) and Lowest Unoccupied Molecular Orbital (LUMO) energies revealed Mulliken charges and charge transfer phenomena occurring within the molecule. Analysis of the Molecular Electrostatic Potential (MEP) unveiled reactive sites, with high electron density regions depicted in red and low electron density regions in blue.

Hyperhardness and hypersoftness of atoms and their ions

ContextThe theory of reactivity based on cDFT has been supplemented with the new method of calculating the atomic and local indices. With the use of previously derived relationship of the electron density gradient to the softness kernel and to the linear response function, we deliver theoretical analysis to obtain significant reactivity indices—the electron density derivatives: local softness and local hypersoftness together with the global hyperhardness index and the derivative of the global softness with respect to the number of electrons. The local derivatives have been applied in the calculation of responses of atoms to perturbation by an external potential by the alchemical approach. The vital role of the local softness has been confirmed; the potential role of the hypersoftness has been indicated.MethodOur original theoretical scheme has been numerically illustrated with the results obtained with electron density calculations with B3LYP method implemented in Gaussian 16 package. The aug-cc-pvqz basis set has been routinely applied, except for the Ca atom (cc-pvqz). Using the pVTZ basis set recommended by Sadlej was necessary for the potassium atom.Graphical

Anticancer activity, DFT calculation, ADMET study and molecular docking of synthetic Chalcone (2E)-1-(4-Aminophenyl)-3-(3,4,5-trimethoxyphenyl)-2- propen-1-one in breast cancer cell line (MCF-7)

The (2E)-1-(4-Aminophenyl)-3-(3,4,5-trimethoxyphenyl)-2-propen-1-one was prepared by the reaction between 4-aminoacetophenone and 3,4,5, trimethoxy benzaldehyde in ethanolic NaOH. Then in vitro anticancer activity was evaluated against the MCF-7 breast cell line. The molecular properties like bond length, bond angle, molecular electrostatic potential surface (MEPs), Mullikan charge, HOMO-LUMO, and NBO analysis data obtained by DFT/B3LYP method using 6- 31+G(d,p) basis set to get electronic states and molecular parameters of the title molecule. Because of their advantageous pharmacokinetic properties, the synthesized compound was shown to have moderate anticancer activity and could advance to a higher level of the drug development process. Molecular docking studies were utilized to foresee the binding interactions of the title compound with the EGFR tyrosine kinase domain (PDB ID: 1M17). In silico ADME study is also performed to predict the pharmacokinetic profile which expressed good oral drug-like behavior.

Millettia aboensis leaves extract as eco-friendly corrosion inhibitor for mild steel in acidizing solution: From experimental to molecular level prediction

The development of environmentally friendly corrosion inhibitors is becoming more popular since conventional inhibitors are poisonous and non-biodegradable. The anti-corrosive effectiveness of Millettia aboensis leaves extract (MALE) has been assessed in this study using several methods, such as electrochemical measurements, X-ray Photoelectron spectroscopy and scanning electron microscopy on mild steel in acidic solution. Gas chromatography-mass spectrometry (GC-MS) analysis was combined with qualitative and quantitative phytochemical analysis to identify the phytochemicals linked to the activity of the Millettia aboensis extracts and identified key phytoconstituents such as Hexanedioic acid, Phenol derivatives, Octadecanoic acid, and Linolenic acid, which play significant roles in the extract's inhibitory performance. The results showed that the inhibition efficiency (IE%) improved to 88.6 % with the addition of inhibitor concentration from 0.1 g/L to 3.0 g/L and that the corrosion rate drastically reduced from 56.91 mpy to 16.09 mpy. Furthermore, at a greater concentration (3.0 g/L), the Rct values rose from 61.42 Ω cm2 to 176.3 Ω cm2 thus, indicating that the inhibitor molecules were forming a protective film over the metallic surface. Scanning Electron Microscopy (SEM) provided visual evidence of surface morphology, revealing a smoother surface in the presence of the inhibitor, indicative of the protective film formed by the adsorption of organic molecules onto the steel surface. Theoretical calculations using the ωB97XD functional and def2svp basis set further supported the experimental findings, showing that the protonated form of C21H36O4 exhibited the highest interaction energy, correlating with its superior inhibition efficiency on the metal surface.

A theoretical and kinetic study of key reactions between ammonia and fuel molecules, part III: H-atom abstraction from esters by ṄH2 radicals

Hydrogen atom abstraction reactions by ṄH2 radicals play a crucial role in determining the reactivity of ammonia/fuel binary blends. Esters are a typical component of environmentally friendly and economically promising biofuels. The feasibility of the ammonia/biofuel dual-fuel approach has been proven in practical engines. [Energy and Fuels 22 (2008) 2963] and [Int. J. Energy Res. 2023 (2023) 9920670]. ṄH2 radicals play a critical role in the combustion and pyrolysis chemistry of ammonia and N-containing-rich fuels. In ammonia/biofuels hybrid combustion, ṄH2 radicals can react with biofuel molecules in a reaction class that is particularly important especially when sufficient ammonia is blended in order to eliminate NOx emissions. To help unravel the chemistry of ammonia/biofuel blends, a systematic theoretical kinetic study of H-atom abstraction from eleven alky esters of CnH2n+1COOCH3 (n = 1–4), CH3COOCmH2m+1 (m = 1–4), and C2H5COOC2H5, by ṄH2 radicals is performed in this work. The geometry optimization, frequency, and zero-point energy calculations for all related species, as well as the hindrance potential energy surface for low frequency torsional modes in the reactants and transition states, were performed at the M06–2X/6–311++G(d,p) level of theory. Intrinsic reaction coordinate calculations were performed to validate the connections between the transition states and expected minima energy species. The energies of all of the species involved were calculated at the QCISD(T)/cc-pVXZ (X = D, T, Q) and MP2/cc-pVYZ (Y = T, Q) levels of theory and then extrapolated to the complete basis set. Rate constants of 39 reactions were calculated using the Master Equation System Solver (MESS) program in the temperature range of 500 – 2000 K. These rate constants for different H-atom abstraction sites are provided and can be extrapolated to larger esters. The kinetic effects from the functional group are also illustrated by performing detailed comparisons with the previous studies of ṄH2 radical reactions with alkanes, alcohols and ethers.

Experimental and computational insight in molecular interactions of imidazolium based deep eutectic solvent with selected alcohols (C1 and C2)

The experimental thermophysical properties (densities (ρ), speed of sound (u) and refractive (nD) indices) of binary mixtures containing 1:3 mol ratio of [1-butyl-3-dimethylimidazolium chloride to ethylene glycol] [BMIM]Cl: EG], deep eutectic solvent (DES), with selected alcohols (methanol and ethanol) were measured. The measurements of the binary mixtures and the pure solvents were conducted at temperatures ranging from (293.15 to 313.15) K in the interval of 5 K and at ambient pressure using an Anton Paar densitometer. Thermodynamic properties such as excess molar volumes (VmE), intermolecular free length (Lf), isentropic compressibilities (ks), deviation in isentropic compressibilities (Δks) and deviation in refractive indices (ΔnD) were computed from the measured data of physical properties. These excess thermodynamic properties are utilized to investigate the intermolecular interactions occurring between imidazolium DES and methanol or ethanol. Geometry optimization calculations were undertaken using Density Functional Theory (DFT) to model the structure of DES with a 1:1 mol ratio employing the B3LYP-D3 functional and a basis set of 6–31G++**. The DFT results revealed that the interaction energies within the DES in the presence of solvent favoured the formation of the complex. Furthermore, interrogation of the optimized structures at molecular level showed that the interactions were mediated by the electrostatic ionic bonding with the co-solvent playing a significant role in solubility. The excess molar volumes of binary mixtures were correlated using the Lorentz-Lorenz equation, and the densities and refractive indices were predicted using the Lorentz-Lorenz equation. The interaction energies and electrostatic interactions between the different solvents were predicted using quantum mechanics. The experimental data was found to be in good agreement with the theoretical data for the measured properties as well as the computational predictions of the stability of the systems.

Exploiting Non-Abelian Point-Group Symmetry to Estimate the Exact Ground-State Correlation Energy of Benzene in a Polarized Split-Valence Triple-Zeta Basis Set.

Local electronic-structure methods in quantum chemistry operate on the ability to compress electron correlations more efficiently in a basis of spatially localized molecular orbitals than in a parent set of canonical orbitals. However, many typical choices of localized orbitals tend to be related by selected, near-exact symmetry operations whenever a molecule belongs to a point group, a feature which remains largely unexploited in most local correlation methods. The present Letter demonstrates how to leverage a recent unitary protocol for enforcing symmetry properties among localized orbitals to yield a high-accuracy estimate of the exact ground-state correlation energy of benzene (D6h) in correlation-consistent polarized basis sets of both double- and triple-ζ quality. Through an initial application to many-body expanded full configuration interaction (MBE-FCI) theory, we show how molecular point-group symmetry can lead to computational savings that are inversely proportional to the order of the point group in a manner generally applicable to the acceleration of modern local correlation methods.

Exploring the interaction of Cu-modified B12N12 nanocages for Favipiravir drug delivery using density functional theory study

Drug delivery has become a pivotal strategy in medical research, aiming for precise delivery near cells while minimizing unwanted effects. In this study, we have used density functional theory (DFT) calculations at the B3LYP/6-311G(d,p) basis set to explore the potential of Cu-modified boron nitride (B12N12) nanocages as smart nanocarriers for delivering the Favipiravir (FAV) drug. This study examined the adsorption energy, electronic features, and thermodynamic properties (ΔG and ΔH) of FAV with B12N12 and Cu-modified B12N12 nanocages, revealing enhanced drug-delivery capacity with notable physisorption and negative adsorption energies. A comprehensive analysis confirmed FAV’s interaction with Cu-modified B12N12 nanocages, involving frontier molecular orbitals, adsorption energy, fractional charge transfer, molecular electrostatic potential (MEP), non-covalent interaction (NCI), and natural bond orbital (NBO) assessments. The analyses of frontier molecular orbitals (FMO), partial density of states (PDOS), and natural bond orbital (NBO) indicate that nanocages act as charge acceptors, while the drug acts as a charge donor during the adsorption process. Among the various Cu-modified B12N12 nanocages studied, Cu-doped CuB11N12 emerged as the most promising candidate for transporting FAV, showcasing notably moderate recovery time (ranging from 29.01 ms to 7.25 s at 298.15 K). Remarkably, the CuB11N12 system exhibited exceptional electronic sensitivity (ΔEgap = 65.38 %) to the FAV drug, surpassing other modified systems. Among the modified cases, the Cu-decorated Cu@b64 and Cu@b66 nanocages showed the most significant decrease in energy levels before and after FAV absorption, reducing from 3.28 eV and 3.33 eV to 1.54 eV and 1.59 eV, respectively. This elucidation may lay the foundation for developing effective drug-delivery systems using nanocages for targeted therapies. In conclusion, this study offers a comprehensive insight into the interaction mechanism between the FAV drug and B12N12, unveiling the potential of Cu-modified B12N12 nanocages as promising candidates for delivering the FAV drug.

Quantitative evaluation of noncovalent interactions with negative fragmentation approach including basis set superposition error correction

Abstract We propose a negative fragmentation approach (NFA), including counterpoise (CP) correction to basis set superposition error (BSSE) for quantitatively evaluating intra- and intermolecular noncovalent interactions. Noncovalent interactions are widely found in chemistry and biology and are regarded as essential interactions. However, there are few general methods for evaluating these individual intra- and intermolecular interaction energies because of two issues: (i) difficulty in the evaluation of intramolecular interactions due to the interacting sites connected with covalent bonds and (ii) BSSE affecting the quantitative accuracy of interaction analysis. In our scheme, we overcome the issue (i) using the NFA scheme, which can evaluate intra- and intermolecular interactions as a fragment–fragment interaction of interacting sites, and address the issue (ii) using the CP method. Here, NFA including the CP correction was applied to various molecular systems, providing comparable results for intermolecular interactions to supermolecule calculations with the CP correction and also succeeding in the evaluation of intramolecular interactions and its BSSEs. It is notable that our NFA scheme does not require any particular program or a modification of the program codes. These indicate that many researchers can apply our NFA scheme to various molecular systems.

Molecular Aspects of the Interactions between Selected Benzodiazepines and Common Adulterants/Diluents: Forensic Application of Theoretical Chemistry Methods.

Benzodiazepines are frequently encountered in crime scenes, often mixed with adulterants and diluents, complicating their analysis. This study investigates the interactions between two benzodiazepines, lorazepam (LOR) and alprazolam (ALP), with common adulterants/diluents (paracetamol, caffeine, glucose, and lactose) using infrared (IR) spectroscopy and quantum chemical methods. The crystallographic structures of LOR and ALP were optimized using several functionals (B3LYP, B3LYP-D3BJ, B3PW91, CAM-B3LYP, M05-2X, and M06-2X) combined with the 6-311++G(d,p) basis set. M05-2X was the most accurate when comparing experimental and theoretical bond lengths and angles. Vibrational and 13C NMR spectra were calculated to validate the functional's applicability. The differences between LOR's experimental and theoretical IR spectra were attributed to intramolecular interactions between LOR monomers, examined through density functional theory (DFT) optimization and quantum theory of atoms in molecules (QTAIM) analysis. Molecular dynamics simulations modeled benzodiazepine-adulterant/diluent systems, predicting the most stable structures, which were further analyzed using QTAIM. The strongest interactions and their effects on IR spectra were identified. Comparisons between experimental and theoretical spectra confirmed spectral changes due to interactions. This study demonstrates the potential of quantum chemical methods in analyzing complex mixtures, elucidating spectral changes, and assessing the structural stability of benzodiazepines in forensic samples.

Experimental, quantum chemical spectroscopic investigation, topological, molecular docking/dynamics and biological assessment studies of 2,6-Dihydroxy-4-methyl quinoline

The present work is a comprehensive investigation of the spectral, electronic structure, bonding, and reactivity of the 2,6-dihydroxy-4-methylquinoline (26DH4MQ) molecule through a wide range of experimental and quantum chemical spectroscopic calculations techniques, along with its applications as nonlinear optical materials and biological assessments. The study utilized density functional theory (DFT) and time-dependent density functional theory (TD-DFT) with the B3LYP method and the 6-311G++(d,p) basis set to analyze the structural and molecular properties of 26DH4MQ. The findings from UV–Vis, FT-IR, and FT-NMR spectroscopy show a strong agreement between the experimentally obtained vibrational frequencies and chemical shifts and those predicted by computational methods. Local reactivity descriptors, such as the dual descriptor, Fukui functions, and the molecular electrostatic potential (MEP) map, were used to identify the reactive regions of the molecule. Additionally, natural bond orbital (NBO) analysis provided insights into the charge transfer characteristics of 26DH4MQ, which helps to stabilize the molecular system. The study also revealed notable nonlinear optical (NLO) properties, with polarizability (18.52 × 10–24e.s.u.) and first-order hyperpolarizability (2.26 × 10–30e.s.u.) values that surpass those of standard organic compounds, suggesting significant potential for optoelectronic applications. The biological evaluation of 26DH4MQ assessed its drug-likeness, toxicity, enzyme inhibition, and ADME (Absorption, Distribution, Metabolism, and Excretion) parameters, highlighting its pharmaceutical potential. Furthermore, molecular docking and dynamics studies illustrated the compound's interaction with proteins, indicating its potential role as an insulin inhibitor.

Optimization of damping function parameters for -D3 and -D4 dispersion models for Hartree-Fock based symmetry-adapted perturbation theory.

Symmetry-adapted perturbation theory (SAPT) directly computes intermolecular interaction energy in terms of electrostatics, exchange-repulsion, induction/polarization, and London dispersion components. In SAPT based on Hartree-Fock ("SAPT0") or based on density functional theory, the most time-consuming step is the computation of the dispersion terms. Previous work has explored the replacement of these expensive dispersion terms with simple damped asymptotic models. We recently examined [Schriber et al. J. Chem. Phys. 154, 234107 (2021)] the accuracy of SAPT0 when replacing its dispersion term with Grimme's popular -D3 correction, reducing the computational cost scaling from O(N5) to O(N3). That work optimized damping function parameters for SAPT0-D3/jun-cc-pVDZ using estimates of the coupled-cluster complete basis set limit [CCSD(T)/CBS] on a 8299 dimer dataset. Here, we explore the accuracy of SAPT0-D3 with additional basis sets, along with an analogous model using -D4. Damping parameters are rather insensitive to basis sets, and the resulting SAPT0-D models are more accurate on average for total interaction energies than SAPT0. Our results are surprising in several respects: (1) improvement of -D4 over -D3 is negligible for these systems, even charged systems where -D4 should, in principle, be more accurate; (2) addition of Axilrod-Teller-Muto terms for three-body dispersion does not improve error statistics for this test set; and (3) SAPT0-D is even more accurate on average for total interaction energies than the much more computationally costly density functional theory based SAPT [SAPT(DFT)] in an aug-cc-pVDZ basis. However, SAPT0 and SAPT0-D3/D4 interaction energies benefit from significant error cancellation between exchange and dispersion terms.

Clusters of solvated ferrous ion in water–ammonia mixture: Structures and noncovalent interactions

The behavior of metal ions is commonly studied in pure solvent although, in our daily life, these metals are involved in mixtures of solvents. In the present study, we investigated structures, relative stabilities and temperature dependance of solvated ferrous ion in water–ammonia mixture solvent at 0K and at various temperatures ranging from 25K to 400K. All the calculations are performed at the MN15 level of theory associated with the aug-cc-pVDZ basis set. For deep understanding of binding patterns in solvated ferrous ion in water–ammonia mixture solvent, noncovalent interactions are presented based on the QTAIM analysis using AIMAll. Our results prove that the ferrous ion is more stable when it is solvated by ammonia instead of water. In addition, hydrogen bonds are weakened by the presence of ammonia molecules. The temperature dependence of the different obtained geometries indicates that from s=6 (s is the sum of water and ammonia molecules around the ferrous ion), when the number of water molecules is almost equal to that of ammonia, the structures with coordination number 5 are dominant. However, the coordination number is six when there are a maximum water molecules (rich water solution) or maximum ammonia molecules (rich ammonia solution) around the ferrous ion (for s≥6). The QTAIM analysis shows that there are two coordination bondings and four hydrogen bondings. Furthermore, it is found that the Fe2+⋯N coordination bondings are stronger than the Fe2+⋯O confirming that the ferrous ion prefers to be solvated by ammonia instead of water.

Asymmetric tridentate Schiff base ligand based mononuclear Zn(II) and Hg(II) complexes: Synthesis, structure, spectroscopic studies, thermal studies, and DFT calculation

Two novel mononuclear metal(II) complexes with an asymmetric tridentate Schiff base ligand, and azide/chloride anions, namely [ZnL(N3)2] (1) and [HgL(Cl)2] (2) (L = (pyridin-2yl)methylimino)-2-ethylpyridine), have been synthesized and structurally characterized by elemental analysis, single crystal X-ray crystallography, FT-IR, NMR, UV–vis electronic absorption spectroscopic analysis. The metal in both the complexes displays a pentacoordination environment realized by the tridentate Schiff base and counter anions. The coordination geometry of Zn in complex 1 is in between a trigonal bipyramidal and square pyramidal, whereas Hg in complex 2 shows a distorted square pyramidal. Theoretical DFT/TD-DFT calculation data performed using B3LYP functional with LanL2MB basis set, compared with values of experimental measurements, have shown a reasonable accord. The thermal stability of both complexes has been studied.

Cu(β-diketonato)2 bathochromic shifts from the ultraviolet towards the visible region

ContextThe DFT-calculated ultraviolet/visible properties of 11 different Cu(β-diketonato)2 complexes are presented. The selected β-diketonato ligands on the Cu complex contain none, one or two aromatic rings. The experimentally measured absorbance maxima range of the ultraviolet/visible is observed at 295–390 nm, and the calculated range is 302–425 nm, for the 11 complexes in this study. More aromatic rings on the ligand lead to bathochromic shifts of the experimentally measured absorbance maxima from the ultraviolet towards the visible region. Absorbance maxima of the Cu(β-diketonato)2 complexes with no aromatic rings on the ligand are found to be predominantly ligand-to-metal charge transfer excitations, whereas introducing one or two aromatic rings shifts the excitations to predominantly ligand-to-ligand charge transfer.MethodsDFT calculations were conducted on the neutral molecules with multiplicity 2, using the PBEh1PBE functional and the aug-cc-pVDZ basis set as implemented in the Gaussian 16 package. The selected solvent was acetonitrile, the solvent in which most of the experimental UV/Vis are reported. The molecules were all optimized in the solvent phase, using the IEFPCM. The initial coordinates for the compounds were generated using Chemcraft.HighlightsTDDFT of 11 different Cu(β-diketonato)2 complexes follow the experimental trend.Aromatic rings on the ligand lead to Bathochromic shifts of UV/Visible spectra.No aromatic rings on the ligand lead to ligand-to-metal charge transfer excitations.Aromatic rings on the ligand lead to ligand-to-ligand charge transfer excitations.Graphical abstractBathochromic shifts in eco-friendly Cu(β-diketonato)2.

Constricting Gaps: Protocol development, implementation challenges and lessons learned for the reality map of unmet needs for Palliative Care Interventions in advanced cancer patients study in Romania and Switzerland

BackgroundPatients with advanced cancer experience many symptoms and needs requiring a Palliative Care Intervention (PCI). Identifying gaps between needs for PCIs and experienced delivery may improve health care, furthermore the association of gaps with quality indicators (QI). The multicentre Romanian (RO)-Swiss (CH) reality map study implemented a novel protocol based on needs concepts and culturally adapted quality indicators (QI). MethodsAn interactive mapping guide measuring unmet needs for PCIs monthly over six months, patient characteristics (cognition, EAPC basic data set, Cofactors) and QI (Inappropriate Anticancer Treatment, High Symptom Burden [IPOS, EQ5D], Repeated ER Admissions, Aggressive End-of-Life Care, and Quality of Death-and-Dying) were developed, applying swiss standards for quality assurance. A composite endpoint (QI, cofactors) was planned. Finally, local solutions responding to gaps were piloted. ResultsFrom 308 patients (RO: 262, CH: 46, age 62j [mean], 74 % ECOG PS 1&2, 81 % current anticancer treatment) baseline and first follow-up data revealed main gaps (symptom management, spiritual needs, family support), country differences (e.g. illness understanding, spiritual needs) and a significant association of the number of gaps with depression. Later data become less, and data quality on QI variable, revealing gaps in research conduct competences, resources, and applicability of over-sophisticated quality assurance tools. Nevertheless, the unmet needs data promoted local initiatives, 81 patients participated in feasibility studies. Finally, the joint experience stimulated academic developments and national integration of palliative care into oncology. ConclusionsPairing motivation and enthusiasm with more modest aims, feasibility testing of all outcomes and investment in research competences may disperse gaps.

Reconciling Accuracy and Feasibility for Barrierless Reaction Steps by the PCS/DDCI/MC-PDFT Protocol: Methane and Ethylene Dissociations as Case Studies.

Several enhancements have been introduced into state-of-the-art computational protocols for the treatment of barrierless reaction steps in the framework of variable reaction coordinate variational transition state theory. The first step is the synergistic integration of the Iterative Difference Dedicated Configuration Interaction (I-DDCI) and Pisa Composite Scheme, which defines a reduced cost, yet very accurate, computational workflow. This approach provides a near black box tool for obtaining 1D reference potentials. Then, a general strategy has been devised for tuning the level of theory used in Monte Carlo (MC) sampling, employing Multiconfiguration Pair Density Functional Theory (MC-PDFT) with dynamically adjusted Hartree-Fock exchange. Concurrently, partial geometry optimizations during the MC simulations account for the coupling between the reaction coordinates and conserved modes. The protocol closely approaches full size consistency and yields highly accurate results, with several test computations suggesting rapid convergence of the I-DDCI correction with the basis set dimensions. The capabilities of the new platform are illustrated by two case studies (the hydrogen dissociation from CH4 and C2H4), which highlight its flexibility in handling different carbon hybridizations (sp3 and sp2). The remarkable accuracy of the computed rate constants confirms the robustness of the proposed method. Together with their intrinsic interest, these results pave the way for systematic investigations of complex gas-phase reactions through a reliable, user-friendly tool accessible to specialists and nonspecialists alike.

Unraveling Strong Supramolecular Assembly of a Novel Pyrene Based Hg(II)‐complex: Insights from Hirshfeld Surface, FMO and Molecular Electrostatic Potential (MEP) Analyses

AbstractA rare pyrene‐based coordination compound of Hg(II) [Hg(L)2] (1) (where, HL=2‐((Pyren‐1‐ylmethylene)amino)benzenethiol) was synthesized and characterized by single crystal X‐ray diffraction (SC‐XRD) analysis. Crystallographic analysis revealed that complex 1 has seesaw geometry with HL coordinated as a bidentate ligand to a metal ion. The role of weak forces like π⋅⋅⋅π and CH⋅⋅⋅π interactions in influencing the self‐assembly process appears to be of importance. The electronic structure of the complex was predicted using DFT calculations with mixed basis set. DFT calculated structural parameters are in good agreement with the experimentally obtained parameters from XRD. Molecular reactivity and stability of the complex has been assessed through frontier molecular orbital analysis. Evaluation of molecular electrostatic potential (MEP) displays the electrophilic and nucleophilic reactivity sites. The Hirshfeld surface analysis clearly indicates C−H⋅⋅⋅π interactions and π⋅⋅⋅π stacking interactions are responsible to extend the supramolecular network of the complex. Analyses of the Finger print plots suggest that H⋅⋅⋅H and H⋅⋅⋅C contacts are major interactions for stabilizing the molecular crystal.

Enzyme Machinery for Bacterial Glucoside Metabolism through a Conserved Non-hydrolytic Pathway.

The flexible acquisition of substrates from nutrient pools is critical for microbes to prevail in competitive environments. To acquire glucose from diverse glycoside and disaccharide substrates, many free-living and symbiotic bacteria have developed, alongside hydrolysis, a non-hydrolytic pathway comprised of four biochemical steps and conferred from a single glycoside utilization gene locus (GUL). Mechanistically, this pathway integrates within the framework of oxidation and reduction at the glucosyl/glucose C3, the eliminative cleavage of the glycosidic bond and the addition of water in two consecutive lyase-catalyzed reactions. Here, based on study of enzymes from the phytopathogen Agrobacterium tumefaciens, we reveal a conserved Mn2+ metallocenter active site in both lyases and identify the structural requirements for specific catalysis to elimination of 3-keto-glucosides and water addition to the resulting 2-hydroxy-3-keto-glycal product, yielding 3-keto-glucose. Extending our search of GUL-encoded putative lyases to the human gut commensal Bacteroides thetaiotaomicron, we discover a Ca2+ metallocenter active site in a putative glycoside hydrolase-like protein and demonstrate its catalytic function in the eliminative cleavage of 3-keto-glucosides of opposite (α) anomeric configuration as preferred by the A. tumefaciens enzyme (β). Structural and biochemical comparisons reveal the molecular-mechanistic origin of 3-keto-glucoside lyase stereo-complementarity. Our findings identify a basic set of GUL-encoded lyases for glucoside metabolism and assign physiological significance to GUL genetic diversity in the bacterial domain of life.