Natural Charges Research Articles

Spectroscopic characterization, DFT study, topological, molecular docking and pharmacological analysis of Iminodiacetic acid Hydrochloride

Iminodiacetic Acid Hydrochloride (IAH) optimum geometries and vibration spectra have been determined by density functional theory computations at B3LYP with 6-311++G(d, p) level basis functions. Finding the most stable structure of IAH is done through conformational analysis. In order to interpret IR and Raman spectra both quantitatively and qualitatively, vibrational spectra have been examined based on the potential energy distribution (PED) within each vibrational mode. By means of calculations both theoretical and experimental, UV–Visible and NMR spectral studies of IAH have been performed. Utilising NBO analysis, stabilisation resulting from inter- and intramolecular interaction has been studied. For predicting the reactivity and stability of the molecule, chemical reactivity descriptors are computed. Molecule size, shape, electrical potential distribution, and point of chemical reactivity will all be revealed by mapping the charge density isosurface well with electrostatic potential surface (ESP). ELF and LOL maps intended topological aspects of IAH have also been depicted. Additionally, the Natural atomic charge and the hyperconjugative interactions that cause its NLO activity have been predicted. The hyper polarizability values indicate that these compounds could be used in electro-optical applications. IAH is screened for its pharmacological activity. The binding location of the molecule to its target protein has been predicted via a molecular docking study.

Fabrication, structural elucidation of some new metal chelates based on N-(1H-Benzoimidazol-2-yl)-guanidine ligand: DNA interaction, pharmaceutical studies and molecular docking approach

New medicinally active chelates were prepared from Cu(II), VO(II), Ag(I) and Pd(II) ions with N-(1H-Benzoimidazol-2-yl)-guanidine, BIG ligand. The ligand performed as bi-dentate or Tri-dentate with various transition metals via (HN– &HN = and N = ) groups. FT-IR &NMR spectra, CHN-analysis, magnetic moment, electronic spectra, TGA, molar conductance and were applied to characterize the studied compounds. Too stability coefficient for BIG chelates had been systematic in solution, besides pH-profile strength shows the more stability of studied chelates. Theoretical study was applied to abstract important features for BIG and its tested complexes. As well as, 3D-plans of MEP, HOMO-LUMO energies, natural nuclear charges, geometrical parameters were calculated over expressed chk-file through (LANL2DZ & 6-311G basis sets) of DFT, In-silico tests were performed using (2vf5& 3cku& 5IJT& 3gcw) proteins to estimate their physiological performance such as grade of connections, docking patterns and associated factors with biological systems. Special attention was demonstrated through the BIGPd chelate in its interaction with amino acid components and drug-like property. Also, the inhibitory performance was assessed through a scoring function. The bioactivity of the tested compounds was detected over contact with DNA that examined through several methods. In-vitro evaluation has been again agreed out through tested compounds beside various microorganisms, BIGPd and BIGAg exhibited high antimicrobial performance. Moreover, their cytotoxic performance has been studied vs. (HCT‐116, HepG-2, as wellMCF‐7) carcinoma strains, elevated inhibitory effect was noticeably verified through BIGPd as well BIGAg chelates. Additionally, antioxidant performance was scanned by DPPH estimation and the tested chelates displayed high acuteness with abduction free radicals. Lastly, such studied chelates may be reflected as favorable bioactive agents.

Investigation on novel natural gas fueled homogeneous charge compression ignition engine based combined power and cooling system

A significant part of energy of fuel supplied is lost in internal combustion engines in the form of atmospheric discharge of engine exhaust gases which are considered as a big source of engine inefficiency and formation of pollutant emissions. To address this issue, a bottoming cycle combining the transcritical CO2 (T-CO2) refrigeration cycle and the supercritical CO2 (sCO2) power cycle is employed, aiming to produce cooling for food preservation by utilizing the exhaust heat of homogeneous charge compression ignition (HCCI) engine powering the refrigerated truck. The operative variables and their effect on thermal and exergetic efficiency of HCCI engine and the combined system are investigated. At the base case operative conditions, the thermal and exergy efficiencies of natural gas fueled HCCI engine are improved significantly from 48.69% to 61.28% and from 41.14% to 42.79%, respectively, after employing the sCO2 powered T-CO2 refrigeration cycle. Promotion of equivalence ratio from 0.3 to 0.9 enhances the thermal and exergy efficiencies of HCCI engine from 47.44% to 49.54% and from 40.14% to 42.12%, respectively. Increasing of engine speed from 1400 r.p.m to 2200 r.p.m provides marginal improvement in HCCI engine efficiencies but the efficiencies of combined cycle are significantly improved from 57.67% to 65.18% and from 40.64% to 45.06%, respectively. Finally, exergy analysis applied to determine the sources of non-idealities within the system revealed that out 361 kW (100%) fuel exergy supplied to the system, HCCI engine destroys 93.31 kW (25.85%), catalytic convertor destroys15.49 kW (4.29%), and the in-cylinder heat transfer losses and system exhaust losses are found as 35.72 kW (9.91%) and 16.61 kW (4.61%), respectively.

Probing the Chemical Bond between Lanthanides and Carbon: CeC, PrC, NdC, LuC, and TmC2.

Resonant two-photon ionization experiments have been conducted to probe the bond dissociation energy (BDE) of the lanthanide-carbon bond, allowing the BDEs of CeC, PrC, NdC, LuC, and Tm-C2 to be measured to high precision. Values of D0(CeC) = 4.893(3) eV, D0(PrC) = 4.052(3) eV, D0(NdC) = 3.596(3) eV, D0(LuC) = 3.685(4) eV, and D0(Tm-C2) = 4.797(6) eV are obtained. Additionally, the adiabatic ionization energy of LuC was measured, giving IE(LuC) = 7.05(3) eV. The electronic structure of these species, along with the previously measured LaC, has been further investigated using quantum chemical calculations. Despite LaC, CeC, PrC, and NdC having ground electronic configurations that differ only in the number of 4f electrons present and have virtually identical bond orders, bond lengths, fundamental stretching frequencies, and metallic oxidation states, a peculiar 1.30 eV range in bond dissociation energies exists for these molecules. A natural bond orbital analysis shows that the metal atoms in these molecules have a natural charge of +1 with a 5d2 4fn 6s0 configuration while the carbon atom has a natural charge of -1 and a 2p3 configuration. The diabatic bond dissociation energies, calculated with respect to the lowest energy level of this separated ion configuration, show a greatly reduced energy range of 0.32 eV, with the diabatic BDE decreasing as the amount of 4f character in the σ-bond increases. Thus, the wide range of measured BDEs for these molecules is a consequence of the variation in atomic promotion energies at the separated ion limit. TmC2 has a smaller BDE than the other LnC2 molecules, due to the tiny amount of 5d participation in the valence molecular orbitals.

Direct observation on argon tagging nitrobenzene radical anion in gas phase: Infrared photodissociation spectroscopy and theoretical calculation.

The infrared photodissociation spectroscopy was applied to characterize nitrobenzene radical anion (NB-). NB- tagged by argon [NB(Ar)-] was prepared by a mixture of nitrobenzene/Ar through a supersonic ion source and then selected by a time-of-flight mass spectrometer. Eight strong peaks observed at 977.9, 999.6, 1059.8, 1275.7, 1309.7, 1339.7, 1367.6 and 1581.7cm-1 in the fingerprint region were assigned to NB(Ar)-, corresponding to CC bending, CC stretching, CC bending+symmetric O-N stretching vibration, antisymmetric O-N and CC stretching vibration, antisymmetric O-N stretching and CH rocking vibration, CC stretching+antisymmetric O-N stretching vibration, C-N stretching vibration, and symmetric CC stretching vibration. Most interestingly, the distinguishable CH stretching vibrations were observed at 3006.5, 3048.6 and 3084.5cm-1 absorptions. Combined with density functional theoretical (DFT) calculation, five tagging argon NB- isomers were optimized and analyzed with no imaginary frequency. The results indicated that most bond lengths in NB- become longer than those of neutral NB, except for the C1-C2/C4-C5 bonds, which are only slightly shorter than those of neutral NB, and the C-N bond, which is 0.085 A shorter in the anion. The NB- tagged by argon located on the nitro group had no change on bond parameters with Ar-tagging or not theoretically. Natural population analysis (NPA) show that the negative natural charges are mainly distributed on both oxygen atoms. And the one electron resonates between the nitro group and benzene ring. N-O bonds in NB- become much more polar than those of the neutral NB. This paper proved the usefulness to characterize NB(Ar)- and further explore the structures of NBn- (n>1) clusters by infrared photodissociation spectroscopy combining with the time-of-flight mass spectrometer.

Ionic, charge transfer interactions, reactivity of the NLO molecule morpholinium perchlorate comparison with morpholinium derivatives using DFT method

In the present study, the compound morpholinium perchlorate (MP) was explored using spectroscopic methods and quantum chemical computations. A TD-DFT method was employed to study the charge transfer ionic interaction strategy to identify the electronic transition exhibited in the UV–visible spectrum, and vibrational analysis of FT-IR and FT-Raman was also measured experimentally. Natural population analysis and molecular electrostatic potential (MEP) surface analysis of the molecule were performed to predict the molecule's reactive site. Natural bond orbital analysis (NBO) and natural charge analysis were used to study the charge transfer interaction. The nature of inter and intramolecular hydrogen bonds are analyzed by using reduced density gradient (RDG), density overlap region indicator (DORI) analysis, and Hirshfeld surface analysis. Electron localization function (ELF) and analysis provide new insight into the chemical bonding of MP. The NLO activity of the studied compound was highlighted by computing the first and second order hyperpolarizability. In the current investigation, the effects of MP and a few morpholinium derivatives were contrasted in terms of molecular geometry, vibrational assessment, HOMO-LUMO energy gap, and NLO effects. According to the results, the MP can be effectively used as an optical limiter in optoelectronics.

Substituent effect on the oxidation and reduction of electronically altered iron(II)-terpyridine derivatives – DFT study

Structure, reactivity, and redox properties play an important role in many biological processes. The structures of two types of series of related iron(II) compounds, namely iron(II)-terpyridine and iron(II)-tris-azinyl derivatives, were optimized in the gaseous as well as solvated states by means of density functional theory (DFT). From the optimized geometries of the molecules, their frontier orbital energies (ELUMO/EHOMO), electronic chemical potential (μ), electrophilicity index, (ω), Merz-Kollman electric potential, Gibbs Free energy, Mulliken and Natural Bond Orbital charges were determined. The DFT calculated reactivity parameters were related to the experimentally reported iron-based oxidation and ligand-based reduction potential of the series of iron(II)-terpyridine and tris-azinyl derivatives. Results obtained show that the relationship between the experimental and DFT calculated Fe(II/III) redox potential gave the most accurate relationship (R2 = 0.97), though a systematic error, depending on the choice of the reference system, was obtained. Relationships between the experimental iron-based oxidation (EFe(II/III)) or ligand-based reduction (ELigand) of the iron(II) complexes, and solvent phase calculated HOMO and LUMO energies respectively (R2 = 0.96 and 0.95 respectively), lead to more accurate relationships with higher R2 values than the relationships involving the gas phase calculations (R2 = 0.87 and 0.88 respectively). More relationships, that can be used to predict the oxidation and reduction of related iron(II) derivatives containing two substituted terpyridine or tris-azinyl analogues of the terpyridine ligand, were obtained to a high accuracy.

Theoretical calculation of the adiabatic electron affinities of the monosubstituted benzaldehyde derivatives

In the current study, several computational models were examined to calculate accurate adiabatic electron affinity (AEA) of twelve m- and p-monosubstituted benzaldehyde derivatives. The examined models are as follows: (i) composite high-level ab initio (G3B3, G4, CBS-Q, and CBS-QB3), (ii) Three hybrid DFT approaches (B3LYP, CAM-B3LYP, and wB97XD) with two basis sets (6–31 + G(d,p) and 6–311++G(2df,2p)) and (iii) single point calculation using fifteen DFT approaches with 6–311++G(2df,2p) at the B3LYP/6–31 + G(d,p) geometry. Several statistical descriptors were computed to validate the calculated AEAs based on the available experimental results. Results revealed that G3B3 and CBS-QB3 are the most accurate result, while G4 and CBS-Q methods yield less accurate ones. Also, the wB97XD and CAM-B3LYP in combination with 6–311++G(2df,2p) able to calculate accurate AEAs. Low CPU time single point calculation strategy by using wb97 and wb97X approaches can compute AEAs value as accurately as G3B3 and CBS-QB3 methods. The AEAs of other several monosubstituted benzaldehydes were also predicted by using the wb97, wb97X, and wb97XD. The effect of the nature and position of substituents on the natural spin density and natural charge is also studied and discussed.

Features of adsorption phenomena in strontium salt solutions in the presence of some cavitands of cucurbituril family

The influence of the electrolyte nature and cation charge on the adsorption properties of cucurbit[6]uril supramolecular complexes are established and discussed. The results show the narrowing of the adsorption potential region of these complexes with increasing cation charge, and the possibility to form an adsorbate layer of supramolecular cations associated with surface-active electrolyte anions at the positive boundary of the adsorption potential region.

Crystal growth and vibrational spectroscopic studies on the novel nlo active piperazine-1,4-diium 3-phenyl-2-propenoate single crystal by experimental and computational technique

An organic nonlinear optical (NLO) single crystal of piperazine-1,4-diium 3-phenyl-2-propenoate (PAPP) is synthesized and delineated by spectroscopic techniques in association with quantum chemical computation. The quantum chemical calculation is performed utilizing density functional theory (DFT) with B3LYP/6-311 G(d,p) basis set. The FT-IR and FT-Raman techniques are adopted to point out the presence of various functional groups in PAPP molecule. The natural bond orbital (NBO), natural charge, molecular electrostatic potential (MEP) and HOMO-LUMO analyses are performed to spot hydrogen bonds and charge transfer interaction present in the molecule. Hole-electron analysis is performed to identify the types of interaction present in the molecule. Interaction region indicator analysis is performed to identify the steric effect, van der Waals force and hydrogen bonds. The optical quality of PAPP single crystal and the band gap energy is found out using UV–visible analysis. The nonlinear optical behaviour of the PAPP molecule is established by evaluating dipole moment, polarizability and hyperpolarizability. The third-order NLO parameters of PAPP crystal are estimated by employing the Z-scan technique.

Semiconductor-hydrophobic material interfaces as a new active site paradigm for photocatalytic degradation of perfluorocarboxylic acids

Photocatalytic degradation of long-chain perfluorocarboxylic acid (PFCA) water contaminants has been reported for numerous of semiconductors, including composite TiO2 particles decorated with graphitic carbon co-catalysts. While pristine TiO2 degrades PFCAs inefficiently, the carbon components purportedly enhance activity due to their conductive nature and resultant charge separation enhancement. Yet herein, we present evidence that the catalytic activity of a graphene oxide (GO)-TiO2 composite from the literature arose not due to from charge separation, but to a unique mode of PFCA adsorption occurring at the interface of TiO2 and hydrophobic GO. Photocatalytic degradation rates by GO-TiO2 were compared to those of composites containing nonconductive polymer microparticles (polyethylene, polytetrafluoroethylene). Results showed that polymer-TiO2 composites performed as well as GO-TiO2 in degrading both perfluorooctanoic acid and oxalate, a common hole scavenger. Thus, the enhanced activity may occur for any TiO2-hydrophobic interface, regardless of co-catalyst conductivity. Furthermore, compared to an unmodified reference catalyst, chain length dependence of PFCA degradation by a polymer-TiO2 composite was found to be less severe, with greater activity toward short-chain species indicating enhanced adsorption behavior. Potential adsorption mechanisms are presented, along with broader implications toward improving the applicability of heterogeneous processes toward a wider range of perfluoroalkyl contaminants.

Iridium/Zinc-Co-Catalyzed Ring-Opening Reactions of Oxabicyclic Alkenes with Indole Nucleophiles: A Combined Experimental and Theoretical Study

An experimental and theoretical investigation on the iridium/zinc-co-catalyzed ring-opening reactions of oxabicyclic alkenes with indole nucleophiles is reported. The reaction affords trans-3-indolyl-1,2-dihydronaphthalen-1-ol products in good yield with no N-alkylated products observed. The C–C bond-forming reaction does not require prior functionalization and is entirely atom-economic. The mechanism and origins of selectivity in the iridium-catalyzed ring-opening reaction have been examined at the M06-D3/Def2TZVPP level of theory. Orbital analysis and natural population analysis charges demonstrate that the Cα site of the π-allyliridium intermediate is the most electrophilic site of attack. Distortion/interaction analysis reveals that the chemoselectivity likely originates from an earlier-stage transition state between Cα and C3, which requires less distortion energy compared to Cα–N1 during the rate-determining intermolecular nucleophilic attack. Moreover, conceptual density functional theory was used to conceptualize the preferential reactive sites of the nucleophiles probed. The C–C bond-forming step is speculated to proceed through a Friedel–Crafts-type reaction.

Adsorption of Diethylstilbestrol Drug into BNNT: DFT/TD-DFT and Spectroscopic (Excited States, UV/Vis and NMR) Studies

Abstract: Cancer has become a significant universal health problem. Anticancer drugs control the chemicals that sacrifice cancer cells by inhibiting their growth in their cell cycle. Interestingly, as much as boron nitride nanosheets and boron nitride nanotubes are degradable and non-toxic, they can act as suitable drug carriers for antitumor drugs and deliver them into target cells. In the present study, the encapsulation of diethylstilbestrol as an anticancer drug into the boron nitride (8,8) nanotube was investigated for the first time using the density functional theory: M06-2X and the natural bond orbital methods in the gas phase. Using natural bond orbital analysis, the charge transfer between diethylstilbestrol drug and boron nitride nanotubes (8,8)/ diethylstilbestrol complex was explored. Based on the results obtained from the calculation of encapsulation energy, it was found that the adsorption process was favorable. The interaction effects of diethylstilbestrol drug and boron nitride (8,8) nanotube on the natural bond orbital charge, the chemical shift parameters, and electronic properties were also evaluated. This study revealed that boron nitride (8,8) nanotubes can be a suitable carrier for diethylstilbestrol drug delivery. The ultra violet-visible spectra of diethylstilbestrol drug and the boron nitride (8,8) nanotubes/diethylstilbestrol complex were computed using time-dependent density functional theory (: M06-2X calculations.

Kajian Morfologi Tanah Sambaran Petir Intensitas Tinggi

Lightning is a dangerous natural phenomenon spreading electric charge from clouds in achieving success. The released charge takes the form of a lightning strike that causes an explosion at ground level. This study aims to describe the physical properties of the soil roughly in terms of (color, bulk density, porosity, texture, structure, pH, and soil moisture) and to describe the physical properties of the soil subtly using SEM (Scanning Electron Microscope) analysis to see the soil diameter and size. soil pores on soil exposed to high-intensity lighting in Sambuli and Purirano villages, Kendari City. This study uses a survey method. At each location, two points were taken, namely soil samples that were struck by high-intensity lightning and soil samples that were not struck by lightning to see changes caused by lightning. The method of measuring physical properties of the soil is measured by a method based on each sample of the physical properties of the soil to see the rough morphology and the Scanning Electron Microscope (SEM) test to see the fine morphology. The results of this study indicate that. Physical properties of high-intensity lightning strike soil in the form of a texture dominated by dusty clay texture has a granular and sub-angular blocky structure, has a bulk density value of 1.41 gr/cm3 – 1.89 gr/cm3 and 1.41 gr/cm3 – 1.74 gr/cm3, has wet soil moisture. Soil color at both locations seen vertically shows a dark color on the surface layer. Has a porosity of 0.470 % - 0.288 % and 0.47% - 0.343 %. The SEM test results showed that the soil particle size was dominated by macropore size with a very fine category. It has an average diameter of 270 μm and 1075 μm.

Metformin-Embedded Biocompatible Chitosan/Poly(vinyl alcohol) Beads with Superior Adsorption Properties toward Lead(II) and Levofloxacin

In this contemporary era, chitosan has gained exceptional attention as a sustainable biopolymer in the adsorption process due to its nontoxic nature, biocompatibility, accessibility, and pH-responsive active surface charge. This study developed a high-performance chitosan/poly(vinyl alcohol) adsorbent through metformin functionalization. The incorporation of poly(vinyl alcohol) (PVA), along with the metformin-activated surface, remarkably ameliorated its physiochemical properties. The abundance of inter- and intrahydrogen and chemical bonds in the porous structure enhances the specific surface area up to 83.8 m2/g. Series characterization methods are utilized to investigate the adsorbents’ characteristics in all aspects and the removal performance. Furthermore, the key factors for the adsorption process, including the influence of pH, adsorbent quantity, time intervals, and preliminary concentration, were studied and optimized. The optimal pH was observed in the neutral moiety, which is crucial from an industrial perspective. Due to the presence of countless nitrogen and oxygen atom-containing backbones, the CS/PVA-Pr-Met biocomposite has demonstrated considerable adsorption capacity toward Pb(II) ions and levofloxacin with the highest adsorption capacities of 313.162 mg/g for Pb(II) and 2872.927 mg/g for levofloxacin concerning their molecular and ionic nature and various adsorption mechanisms. In accordance with the correlation coefficient and estimated parameters, the adsorption of Pb(II) and levofloxacin onto the beads mostly follows the pseudo-second-order kinetics (R2 ≥ 0.997) and the Langmuir adsorption isotherm model (R2 ≥ 0.995). The exceptional adsorption capacity coupled with the porous structure of the modified hydrogel beads has promising applications for efficient wastewater treatment

Microhydration of the Pyrrole Cation (Py+) Revealed by IR Spectroscopy: Ionization-Induced Rearrangement of the Hydrogen-Bonded Network of Py+(H2O)2

Microhydration of heterocyclic aromatic molecules can be an appropriate fundamental model to shed light on intermolecular interactions and functions of macromolecules and biomolecules. We characterize herein the microhydration process of the pyrrole cation (Py+) by infrared photodissociation (IRPD) spectroscopy and dispersion-corrected density functional theory calculations (B3LYP-D3/aug-cc-pVTZ). Analysis of IRPD spectra of mass-selected Py+(H2O)2 and its cold Ar-tagged cluster in the NH and OH stretch range combined with geometric parameters of intermolecular structures, binding energies, and natural atomic charge distribution provides a clear picture of the growth of the hydration shell and cooperativity effects. Py+(H2O)2 is formed by stepwise hydration of the acidic NH group of Py+ by a hydrogen-bonded (H2O)2 chain with NH···OH···OH configuration. In this linear H-bonded hydration chain, strong cooperativity, mainly arising from the positive charge, strengthens both the NH···O and OH···O H-bonds with respect to those of Py+H2O and (H2O)2, respectively. The linear chain structure of the Py+(H2O)2 cation is discussed in terms of the ionization-induced rearrangement of the hydration shell of the neutral Py(H2O)2 global minimum characterized by the so-called "σ-π bridge structure" featuring a cyclic NH···OH···OH···π H-bonded network. Emission of the π electron from Py by ionization generates a repulsive interaction between the positive π site of Py+ and the π-bonded OH hydrogen of (H2O)2, thereby breaking this OH···π hydrogen bond and driving the hydration structure toward the linear chain motif of the global minimum on the cation potential.

Photovoltaic characteristics of organic heterocyclic 2,9-dimethyl quinacridone in different solvents using DFT approach

In this work, efforts had been made to develop the photovoltaic utility of 2,9-dimethyl quinacridone (2,9-DMQA) using density functional theory (DFT). Initially, the structural analysis was done using the molecule's ground state geometry to study the molecule's structural characteristics. In particular, the global reactivity descriptors, density of states (DOS) analysis, molecular electrostatic potential (MEP), contour plot, and, ionization potential surface, dipole moment, Mulliken, and natural charge distribution, were computed and analyzed to identify the nucleophilic and electrophilic sites of the molecule. Considering N – H the donor and C = O the acceptor group, the intramolecular charge transfer (ICT) was established. Hirshfeld surfaces and fingerprint plots were also determined to explore intermolecular interactions. The electronic transitions were analyzed using the simulated absorption and emission spectra. To better understand the role of solvents in inducing the photovoltaic property, the light-harvesting efficiency of the molecules was computed in the considered solvents. The title molecule provided light harvesting efficiency in order of chloroform > ethanol > cyclohexane. Other photovoltaic properties were also computed to predict the power conversion efficiency of the molecule. Consequently, the title molecule offers a strong charge conduction ability and effective electron transport from the donor to the acceptor. The obtained results were favorable enough to test experimentally 2,9-DMQA which could be used as a photosensitizer in dye-synthesized solar cells and could enhance the performance of organic photovoltaic cells.

Metal Atoms (Li, Na, and K) Tuning the Configuration of Pyrrole for the Selective Recognition of C60

Host-guest structure assembly is significant in the recognition of molecules, and the fullerene-based host-guest structure is a convenient method to determine the structures of fullerenes of which recognition is with many difficulties in experiments. Here, with density functional theory calculations, we designed several crown-shaped pyrrole-based hosts tuned by doping metal atoms (Li, Na, and K) for the effective recognition of C60 with modest interaction between the host and guest. Binding energy calculations showed an enhanced interaction of the concave-convex host-guest system with the doped metal atoms, enabling the selective recognition of C60. The electrostatic interaction between the host and guest was studied by the natural bond order charge analysis, reduced density gradient, and electrostatic potential. Furthermore, the UV-vis-NIR spectra of host-guest structures were simulated to give guidance on the release of the fullerene guest. With much expectation, this work would give a new strategy to design new hosts for effectively recognizing much more fullerene molecules with modest interaction and would be useful for the assembly involving fullerenes.

Seed-mediated strategy for synthesis of enzyme-encapsulated metal-organic frameworks with enhanced enzyme activity

Encapsulation of enzymes into metal-organic frameworks (enzyme@MOF) can improve the stability of enzymes. Most present synthesis methods of enzyme@MOF rely on the complex modification of enzymes or the natural negative surface charge of enzymes to promote the synthesis of enzyme@MOF. Despite extensive efforts, it remains challenging to develop a surface charge-independent and convenient strategy to encapsulate various enzymes into MOF efficiently. In this study, we proposed a convenient seed-mediated strategy for efficient synthesis of enzyme@MOF from the perspective of MOF formation. The seed, acting as nuclei, makes the slow nucleation stage skipped, leading to the efficient synthesis of enzyme@MOF. The successful encapsulation of several proteins demonstrated the feasibility and advantages of the seed-mediated strategy. Moreover, the resulting composite, cytochrome (Cyt c) encapsulated in ZIF-8, exhibited a 5.6-fold increase in bioactivity compared to free Cyt c. The seed-mediated strategy provides an efficient, enzyme surface charge-independent, and non-modified method for the synthesis of enzyme@MOF biomaterials, which warrants further exploration and application in diverse fields.

Synthesis, X-ray crystal structure, Hirshfeld surface analysis and computational investigation into the potential inhibitory action of novel 6-(p-tolyl)-2-((p-tolyl)thio)methyl-7H-[1.2.4]triazolo[5,1-b][1,3,4]thiadiazine inhibits the main protease of COVID-19

In recent times, the novel coronavirus disease (COVID-19) caused by the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has now become a worldwide pandemic. With over 71 million confirmed cases, even though the effectiveness and side effects of the specific drugs and vaccines approved for this disease are still limited. Scientists and researchers from all across the world are working to find a vaccine and a cure for COVID-19 by using large-scale drug discovery and analysis. Heterocyclic compounds are regarded to be valuable sources for the discovery of new antiviral medications against SARS-CoV-2 because virus occurrences are still on the rise, and infectivity and mortality may also rise shortly. In this regard, we have synthesized a new triazolothiadiazine derivative. The structure was characterized by NMR spectra and confirmed by X-ray diffraction analysis. The structural geometry coordinates of the title compound are well reproduced by DFT calculations. NBO and NPA analyses have been performed to determine the interaction energies between bonding and antibonding orbital, and natural atomic charges of heavy atoms. Molecular docking suggests that the compounds may have good affinity for SAR-CoV-2 main protease, RNA-dependent RNA polymerase and nucleocapsid enzymes, particularly the main protease enzyme (binding energy of −11.9 kcal mol−1). The predicted docked pose of the compound is dynamically stable and reports a major van der Waals contribution (−62.00 kcal mol−1) to overall net energy.Communicated by Ramaswamy H. Sarma