Quantum Chemistry Based Computational Study on the Conformational Population of a Neodymium Neodecanoate Complex

The title complex is widely used as an efficient key component of Ziegler-Natta catalyst for stereospecific polymerization of dienes to produce synthetic rubbers. However, the quantitative structure-activity relationship（QSAR） of this kind of complexes is still not clear mainly due to the difficulties to obtain their geometric molecular structures through laboratory experiments. An alternative solution is the quantum chemistry calculation in which the comformational population shall be determined. In this study, ten conformers of the title complex were obtained with the function of molecular dynamics conformational search in Gabedit 2.4.8, and their geometry optimization and thermodynamics calculation were made with a Sparkle/PM7 approach in MOPAC 2012. Their Gibbs free energies at 1 atm. and 298.15 K were calculated. Population of the conformers was further calculated out according to the theory of Boltzmann distribution, indicating that one of the ten conformers has a dominant population of 77.13%.

Effect of solvent on the initiation mechanism of living anionic polymerization of styrene:A computational study

For living anionic polymerization(LAP),solvent has a great influence on both reaction mechanism and kinetics.In this work,by using the classical butyl lithium-styrene polymerization as a model system,the effect of solvent on the mechanism and kinetics of LAP was revealed through a strategy combining density functional theory(DFT)calculations and kinetic modeling.In terms of mechanism,it is found that the stronger the solvent polarity,the more electrons transfer from initiator to solvent through detailed energy decomposition analysis of electrostatic interactions between initiator and solvent molecules.Furthermore,we also found that the stronger the solvent polarity,the higher the monomer initiation energy barrier and the smaller the initiation rate coefficient.Counterintuitively,initiation is more favorable at lower temperatures based on the calculated results ofΔG_(TS).Finally,the kinetic characteristics in different solvents were further examined by kinetic modeling.It is found that in benzene and n-pentane,the polymerization rate exhibits first-order kinetics.While,slow initiation and fast propagation were observed in tetrahydrofuran(THF)due to the slow free ion formation rate,leading to a deviation from first-order kinetics.

Mechanism of dibenzofuran hydrodeoxygenation on the Ni(1 1 1)surface

The low-temperature coal tar contains a considerable number of oxygen-containing compounds,which results in poor quality.The catalytic hydrodeoxygenation of oxygen-containing compound to an added-value chemical compound is one of the most efficient methods to upgrade coal tar.In this study,density functional theory calculations are employed to assess and analyze in detail the hydrodeoxygenation of dibenzofuran,as a model compound of coal tar,on the Ni(111)surface.The obtained results indicate that dibenzofuran can be firstly hydrogenated to tetra hy d rod i be nzofura n and hexahydfodibenzofufan.The five-membered-ring opening reaction of tetrahydrodibenzofuran is more straightforward than that of hexahydrodibenzofuran(Ea=0.71 eV vs.1.66 eV).Then,both pathways generate an intermediate 2-cyclohexylphenoxy compound.One part of 2-cyclohexylphenoxy is hydrogenated to 2-cyclohexylphenol and consecutively hydrogenated to cyclohexylcyclohexanol,and another part is directly hydrogenated to cyclohexylcyclohexanone.The hydrogenated intermediates of2-cyclohexylphenol have higher deoxygenation barriers than 2-cyclohexylphenol and cyclohexylcy clohexanol.During the hydrogenation process of cyclohexylcyclohexanone to cyclohexylcyclohexanol,the intermediate 26,formed by adding H to O atom of cyclohexylcyclohexanone,exhibits the lowest deoxygenation barrier of 1.08 eV.High hydrogen coverage may promote the hydrogenation of tetrahydrodibenzofuran,hexahydrodibenzofuran,and intermediate 26 to generate dodecahydrodibenzofuran and cyclohexylcyclohexanol.This dibenzofuran hydrodeoxygenation reaction mechanism corroborates well with previous experimental results and provides a theoretical basis for further optimization of the design of nickel-based catalysts.

High-efficiency separation and extraction of naphthenic acid from high acid oils using imidazolium carbonate ionic liquids

N-alkyl imidazolium carbonate ionic liquids were employed to separate and recover naphthenic acid from model oils.The effects of the cationic and anionic structures of ionic liquids and operating conditions on the deacidification performance were investigated.The deacidification performance of traditional organic solvents was also investigated for comparison.The results indicated that the naphthenic acid could be completely removed from the model oil with a small mass ratio of ionic liquid to oil.The extracted naphthenic acid was regenerated with a recovery of up to 92%.In addition,imidazolium carbonate ionic liquids could be successfully regenerated and recycled.The mechanism of interaction between imidazole ionic liquids and the naphthenic acid molecules were explained by Gauss calculation.

Theoretical Investigations of La_2C_2 Cluster

Possible structures of La 2C 2 were studied and proposed by use of density functional theory. All proposed isomers are planar. The results indicate that the structure with the lowest symmetry ( C 1) is the most stable. Linear isomers are not favored .

Theoretical Studies on Two Possible Conformers of TNDAIW at Hartree-Fock Level

Tetranitrodiazidoacetylhexaazaisowurtzitane (TNDAIW) is a novel polyazapolycyclic caged polyazidonitramine explosive first synthesized in our laboratory. Two possible conformers of TNDAIW with C_s symmetry were fully optimized using the HF/6-31G(d) level of theory. TNDAIW with the optimized geometries probably exists, and is predicted to be more stable than epsilon-hexanitrohexaazoisowurtzitane (epsilon-CL-20) based on the lengths of N-N, C-C and C-N bonds. The impact and shock sensitivities are lower for the possible conformers of TNDAIW than those for epsilon-CL-20. TNDAIW with the optimized possible conformers is estimated to be a promising novel high energy density explosive.

Chiral Recognition of Dansyl Derivatives with an Amino Acid-Based Molecular Micelle: A Molecular Dynamics Investigation

In this study, the chiral separation mechanisms of Dansyl amino acids, including Dansyl-Leucine (Dans-Leu), Dansyl-Norleucine (Dans-Nor), Dansyl-Tryptophan (Dans-Trp) and Dansyl-Phenylalanine (Dans-Phe) binding to poly-sodium N-undecanoyl-(L)-Leucylvalinate, poly (SULV), were investigated using molecular dynamics simulations. Micellar electrokinetic chromatography (MEKC) has previously shown that when separating the enantiomers of these aforementioned Dansyl amino acids, the L-enantiomers bind stronger to poly (SULV) than the D-enantiomers. This study aims to investigate the molecular interactions that govern chiral recognition in these systems using computational methods. This study reveals that the computationally-calculated binding free energy values for Dansyl enantiomers binding to poly (SULV) are in agreement with the enantiomeric order produced in experimental MEKC studies. The L-enantiomers of Dans-Leu, Dans-Nor, Dans-Trp, and Dans-Phe binding to their preferred binding pockets in poly (SULV) yielded binding free energy values of -21.8938, -22.1763, -21.3329 and -13.3349 kJ·mol-1, respectively. The D-enantiomers of Dans-Leu, Dans-Nor, Dans-Trp, and Dans-Phe binding to their preferred binding pockets in poly (SULV) yielded binding free energy values of -14.5811, -15.9457, -13.6408, and -12.0959 kJ·mol-1, respectively. Furthermore, hydrogen bonding analyses were used to investigate and elucidate the molecular interactions that govern chiral recognition in these molecular systems.

DFT Studies on Molecular Structure, Thermodynamics Parameters, HOMO-LUMO and Spectral Analysis of Pharmaceuticals Compound Quinoline (Benzo[b]Pyridine)

Advances in computational chemistry have greatly increased its effectiveness and attractiveness as an emerging adjunct to experimental chemistry but also as an independent research field. This work studied some basic bonding Parameters, geometry, Uv-Visible spectra, HOMO-LUMO and harmonic vibrational frequencies of Quinoline were investigated by using density functional theory (DFT/6-31+ (d, p)) methods. The calculated wave numbers (B3LYP) agree properly with the determined wave numbers. The results obtained are then as compared with experimental statistics in which available. The structural parameters;thermochemistry, rotational constants, IR spectra and frequencies, bond distances, angles and dipole moment were obtained from the optimized stable geometries of the compound. The computed optimized geometric bond lengths and bond angles show good agreement with experimental data of the title compound. The calculated HOMO and LUMO energies indicate that charge transfer occurs within the molecule.

Toward the Uniform of Chemical Theory,Simulation,and Experiments in Metaverse Technology

In recent years,with the continuous development of artificial intelligence(AI)technology,the digital process in chemistry has also changed with each passing day.However,the current digitalization of chemistry mainly uses AI technology to assist some scientific research related to computational chemistry,such as molecular design,catalyst design,reaction route design,etc.There is still no clear digital route to connect with experimental chemistry;digitization in experimental and theoretical chemistry is still in its infancy.This work sorts out some of the main references and logic of the digitalization of experimental chemistry.It puts forward a central point:in a truly digital world,there is no boundary between chemical experiments,theory,and calculation.The Mateverse platform based on Metaverse technology makes all of this possible,primarily through a digital process assisted by human researchers,which will significantly change the research paradigm of chemistry.Metaverse is a technology that should not be ignored for the future development of chemistry,which is impelled by the merged data from experiments,simulations,and theory.

Machine learning of organic solvents reveals an extraordinary axis in Hansen space as indicator of spherical precipitation of polymers

Machine learning is an emerging tool in the field of materials chemistry for uncovering a principle from large datasets.Here,we focus on the spherical precipitation behavior of polymers and computationally extract a hidden trend that is orthogonal to the availability bias in the chemical space.For constructing a dataset,four polymers were precipitated from 416 solvent/nonsolvent combinations,and the morphology of the resulting precipitates were collected.The dataset was subjected to computational investigations consisting of principal component analysis and machine learning based on random forest model and support vector machine.Thereby,we eliminated the effect of the availability bias and found a linear combination of Hansen parameters to be the most suitable variable for predicting precipitation behavior.The predicted appropriate solvents are those with low hydrogen bonding capability,low polarity,and small molecular volume.Furthermore,we found that the capability for spherical precipitation is orthogonal to the availability bias and forms an extraordinary axis in Hansen space,which is the origin of the conventional difficulty in identifying the trend.The extraordinary axis points toward a void region,indicating the potential value of synthesizing novel solvents located therein.

Intra-Ring Bridging:A Strategy for Molecular Design of Highly Energetic Nitramines

Main observation and conclusion Important progress has been made in the development of energetic molecules with high performance by computer-aided molecular design in recent years,but structural novelty of organic scaffolds is insufficient.In this work,we propose an intra-ring bridging strategy inspired by the known energetic nitramines to design novel polycyclic and cage energetic molecules.More than 100 energetic structures were designed by introducing the C—C bridges and increasing the ring size.The synthesis difficulty is considered besides the two most concerned properties of EMs,energy and safety.After a comprehensive estimation,a symmetric cage molecule labeled as 8U-30 was finally selected because of its relatively high detonation performance,and comparable impact sensitivity as well as synthetic accessibility with CL-20.Hopefully,the proposed strategy could be utilized in further molecular design to gain various scaffolds,especially cage structures,for different demands.

Emerging approaches to probing ion channel structure and function

Ion channels,as membrane proteins,are the sensors of the cell.They act as the first line of communication with the world beyond the plasma membrane and transduce changes in the external and internal environments into unique electrical signals to shape the responses of excitable cells.Because of their importance in cellular communication,ion channels have been intensively studied at the structural and functional levels.Here,we summarize the diverse approaches,including molecular and cellular,chemical,optical,biophysical,and computational,used to probe the structural and functional rearrangements that occur during channel activation（or sensitization）,inactivation（or desensitization）,and various forms of modulation.The emerging insights into the structure and function of ion channels by multidisciplinary approaches allow the development of new pharmacotherapies as well as new tools useful in controlling cellular activity.

Facile Access to Uranium and Thorium Phosphaethynolate Complexes Supported by Tren: Experimental and Theoretical Study

The issue of covale nee of acti nide complexes remai ns con troversial to date.The in troducti on of 2-phosphaethy nolate anion into acti・nide complexes is expected to in vestigate the reaction mode and the bon ding property.Herei n,we describe the function alizatio n of An(Tren^(TIPS))CI(1:An=U;2:An=Th)precursors with NaOCP(dioxane)_(2.5) through salt-elimination method leading to the formation of the corresponding uranium and thorium phosphaethynolate species:[U(Tren^(TIPS))(OCP)]⑶and[Th(Tren^(TIPS))(OCP)](4).

SPONGE:A GPU-Accelerated Molecular Dynamics Package with Enhanced Sampling and AI-Driven Algorithms

SPONGE(Simulation Package tOward Next GEneration molecular modeling)is a software package for molecular dynamics(MD)simulation of solution and surface molecular systems.In this version of SPONGE,the all-atom potential energy functions used in AMBER MD packages are used by default and other all-atom/coarse-grained potential energy functions are also supported.SPONGE is designed to extend the timescale being approached in MD simulations by utilizing the latest CUDA-enabled graphical processing units(GPU)and adopting highly efficient enhanced sampling algorithms,such as integrated tempering,selective integrated tempering and enhanced sampling of reactive trajectories.It is highly modular and new algorithms and functions can be incorporated con veniently.Particularly,a specialized Python plugin can be easily used to perform the machine learning MD simulation with MindSpore,TensorFlow,PyTorch or other popular machine learning frameworks.Furthermore,a plugin of Finite-Element Method(FEM)is also available to handle metallic surface systems.All these advanced features increase the power of SPONGE for modeling and simulation of complex chemical and biological systems.

Estimation of Stability Constants of Copper（Ⅱ） Complexes with a-Amino Acids Using Connectivity Index 3xV, Common Model for the Binary and Ternary Complexes

Models for estimation of the first （K1）, second （K2）, and overall stability constant （β2） of copper（II） chelates with naturally occurring amino acids, based on the valence connectivity index of the 3rd order （3Xr）, were improved by introduction of a square term and a new graph representation for mono-complexes （MLCor）. The models gave SE = 0.07, 0.05--0.07 and 0.05--0.08 for lg Ki, lg K2 and lg ,62 constants, respectively; models that encompass both bi- nary and ternary bis-complexes included indicator variable. We also validated our models on the test set which in- cluded two mono-, two binary and two ternary Cu（II） chelates with a-aminobutanoic acid and a-aminopentanoic acid, not included into the calibration. The absolute differences between experimental and predicted stability con- stants were in the range of 0.01--0.16.

Near Infrared Spectral Similarity Combined with Variable Se- lection Method in the Quality Control of Flos Lonicerae： A Preliminary Study

This paper indicates the possibility to use near infrared （NIR） spectral similarity as a rapid method to estimate the quality of Flos Lonicerae. Variable selection together with modelling techniques is utilized to select representative variables that are used to calculate the similarity. NIR is used to build calibration models to predict the bacte-riostatic activity of Flos Lonicerae. For the determination of the bacteriostatic activity, the in vitro experiment is used. Models are built for the Gram-positive bacteria and also for the Gram-negative bacteria. A genetic algorithm combined with partial least squares regression （GA-PLS） is used to perform the calibration. The results of GA-PLS models are compared to interval partial least squares （iPLS） models, full-spectrum PLS and full-spectrum principal component regression （PCR） models. Then, the variables in the two GA-PLS models are combined and then used to calculate the NIR spectral similarity of samples. The similarity based on the characteristic variables and full spec- trum is used for evaluating the fingerprints of Flos Lonicerae, respectively. The results show that the combination of variable selection method, modelling techniques and similarity analysis might be a powerful tool for quality control of traditional Chinese medicine （TCM）.

Neural Network Representations for Studying Gas-Surface Reaction Dynamics:Beyond the Born-Oppenheimer Static Surface Approximation

In the past a few years,there has been significant progress in theoretical characterizations of gas-surface reaction dynamics at the atomic level.One of the major breakthroughs is the machine learning representations of the potential energy surfaces and related properties for molecules on metal surfaces from first-principles,particularly neural networks based methods.In this review,we focus on recent advances of the development and applications of high-dimensional symmetry-preserving neural network representations in gas-surface systems,which have enabled efficient Born-Oppenheimer molecular dynamics simulations with inclusion of all molecular and surface degrees of freedom,as well as some nonadiabatic molecular dynamics simulations with effective treatment of hot electrons,at the density function theory level.Despite these advances,further challenges remain.More accurate electronic structure theories and more efficient machine learning(and active learning)algorithms are needed towards a more quantitative description of more complex gas-surface reactions involving multiple surfaces and adsorbates or multiple electronic states.

DFT/TDDFT Studies on the Electronic Structures and Spectral Properties of Carbazole-based Blue Light-emitting Dendrimers

The purpose of this paper is to provide an in-depth investigation of the electronic and optical properties of two series of carbazole-based blue light-emitting dendrimers, including 1--6 six oligomers. These materials show great potential for application in organic light-emitting diodes as efficient blue-light and red-light emitting materials due to the tuning of the optical and electronic properties by the use of different electron donors （D） and electron acceptors （A）. The geometric and electronic structures of these compounds in the ground state are calculated using density functional theory （DFT） and the ab initio HF, whereas the lowest singlet excited states were optimized by ab initio single excitation configuration interaction （CIS）. All DFF calculations are performed using the B3LYP functional on 6-31G＊ basis set. The outcomes show that the highest occupied molecular orbitals （HOMOs）, lowest occupied molecular orbitals （LUMOs）, energies gaps, ionization potentials, electron affinities and reorganization energies of each molecular are affected by different D and A moieties and different substitute positions.

Combined Transient Spectra and Semiempirical Calculation of [60]Fullerenes Attached with Piperidinodithiocarboxylate and 7-Chloro-phenazine

[60]Fullerenes attached with piperidinodithiocarboxylate dyad （1） and 7-chloro-1,2,3,4-tetrahydrophenazine （2） were efficiently synthesized through Diels-Atder cycloaddition with dienes. The physical properties of the triplet states of these compounds, in which strong electron acceptor moieties were covalently attached to C60 cores, were investigated by nanosecond laser flash photolysis. The excited triplet states in benzonitrite have been evaluated by observing the transient absorption bands in the near-IR region. The HOMO and LUMO were calculated by semiempirical methods AM1, which could predict the intramolecular photoinduced electron transfer in 1 and 2, and the nanosecond transient absorption spectra observed experimentally in solution were in excellent agreement with the calculated ones.

State-crossing from a Locally Excited to an Electron Transfer State(SLEET)Model Rationalizing the Aggregation-induced Emission Mechanism of(Bi)piperidylanthracenes

Luminogens with aggregation-induced emission(AIE)characteristics(or AIEgens)have been widely used in various applications due to their excellent luminescent properties in molecular aggregates and the solid state.A deep understanding of the AIE mechanism is critical for the rational development of AIEgens.In this work,the“state-crossing from a locally excited to an electron transfer state”(SLEET)model is employed to rationalize the AIE phenomenon of two(bi)piperidylanthracenes.According to the SLEET model,an electron transfer(ET)state is formed along with the rotation of the piperidyl group in the excited state of(bi)piperidylan-thracene monomers,leading to fluorescence quenching.In contrast,a bright state exists in the crystal and molecular aggregates of these compounds,as the intermolecular interactions restrict the formation of the dark ET state.This mechanistic understanding could inspire the deployment of the SLEET model in the rational designs of various functional AIEgens.