Isotropic Shifts Research Articles

Machine Learning Full NMR Chemical Shift Tensors of Silicon Oxides with Equivariant Graph Neural Networks.

The nuclear magnetic resonance (NMR) chemical shift tensor is a highly sensitive probe of the electronic structure of an atom and furthermore its local structure. Recently, machine learning has been applied to NMR in the prediction of isotropic chemical shifts from a structure. Current machine learning models, however, often ignore the full chemical shift tensor for the easier-to-predict isotropic chemical shift, effectively ignoring a multitude of structural information available in the NMR chemical shift tensor. Here we use an equivariant graph neural network (GNN) to predict full 29Si chemical shift tensors in silicate materials. The equivariant GNN model predicts full tensors to a mean absolute error of 1.05 ppm and is able to accurately determine the magnitude, anisotropy, and tensor orientation in a diverse set of silicon oxide local structures. When compared with other models, the equivariant GNN model outperforms the state-of-the-art machine learning models by 53%. The equivariant GNN model also outperforms historic analytical models by 57% for isotropic chemical shift and 91% for anisotropy. The software is available as a simple-to-use open-source repository, allowing similar models to be created and trained with ease.

Ligand-Capped Cobalt(II) Multiplies the Value of the Double-Histidine Motif for PCS NMR Studies.

In structural studies by NMR, pseudocontact shifts (PCSs) provide both angular and distance information. For proteins, incorporation of a di-histidine (diHis) motif, coordinated to Co2+, has emerged as an important tool to measure PCS. Here, we show that using different Co(II)-chelating ligands, such as nitrilotriacetic acid (NTA) and iminodiacetic acid (IDA), resolves the isosurface ambiguity of Co2+-diHis and yields orthogonal PCS data sets with different Δχ-tensors for the same diHis-bearing protein. Importantly, such capping ligands effectively eliminate undesired intermolecular interactions, which can be detrimental to PCS studies. Devising and employing ligand-capping strategies afford versatile and powerful means to obtain multiple orthogonal PCS data sets, significantly extending the use of the diHis motif for structural studies by NMR.

Nature of NMR Shifts in Paramagnetic Octahedral Ru(III) Complexes with Axial Pyridine-Based Ligands.

In recent decades, transition-metal coordination compounds have been extensively studied for their antitumor and antimetastatic activities. In this work, we synthesized a set of symmetric and asymmetric Ru(III) and Rh(III) coordination compounds of the general structure (Na+/K+/PPh4+/LH+) [trans-MIIIL(eq)nL(ax)2]- (M = RuIII or RhIII; L(eq) = Cl, n = 4; L(eq) = ox, n = 2; L(ax) = 4-R-pyridine, R = CH3, H, C6H5, COOH, CF3, CN; L(ax) = DMSO-S) and systematically investigated their structure, stability, and NMR properties. 1H and 13C NMR spectra measured at various temperatures were used to break down the total NMR shifts into the orbital (temperature-independent) and hyperfine (temperature-dependent) contributions. The hyperfine NMR shifts for paramagnetic Ru(III) compounds were analyzed in detail using relativistic density functional theory (DFT). The effects of (i) the 4-R substituent of pyridine, (ii) the axial trans ligand L(ax), and (iii) the equatorial ligands L(eq) on the distribution of spin density reflected in the "through-bond" (contact) and the "through-space" (pseudocontact) contributions to the hyperfine NMR shifts of the individual atoms of the pyridine ligands are rationalized. Further, we demonstrate the large effects of the solvent on the hyperfine NMR shifts and discuss our observations in the general context of the paramagnetic NMR spectroscopy of transition-metal complexes.

Creating Solid Solutions of Metallocenes: Migration of Nickelocene into the Ferrocene Crystal Lattice in the Absence of a Solvent

Ferrocene and nickelocene do not react with each other in solution; however, the large impact of the paramagnetic component on the ferrocene 1H NMR signal linewidth and relaxation times has been quantified. Co-crystallization of ferrocene and nickelocene at any ratio from a solvent can be explained with both pure substances crystallizing in the same space group P21/n. As a new phenomenon, when a ferrocene single crystal is exposed to polycrystalline nickelocene in the absence of a solvent, the nickelocene migrates into the ferrocene crystal lattice and a mixed crystal is formed that retains its macroscopic shape. This process has been proven visually by cutting the single crystal. Mixing polycrystalline ferrocene with polycrystalline nickelocene at different molar ratios with a mortar and pestle leads to crystalline solid solutions with the corresponding molar ratios of both components. This migration of one organometallic component into an existing crystal lattice of another at ambient temperature in the absence of a solvent has not been described previously. Paramagnetic 1H solid-state NMR spectroscopy of static and rotating samples of dry ferrocene/nickelocene mixtures at varying ratios is used to prove and quantify the mixing of both metallocenes at the molecular level. A single-crystal X-ray structure of a 50/50 mixed crystal corroborates the NMR results that nickelocene and ferrocene are randomly distributed in the lattice and that the space group P21/n is retained. All ferrocene molecules in the mixed crystal lattice show a broadening of their 1H wideline signals and residual magic-angle spinning (MAS) lines at ambient temperature. The broadening of the ferrocene signals correlates with the nickelocene content. 1H T1 relaxation time measurements for the signals of ferrocene in samples with different amounts of nickelocene corroborate the assumption that the signal broadening is due to paramagnetic dipole–dipole relaxation of ferrocene molecules in the vicinity of nickelocene. Spatially separated ferrocene and nickelocene powders in one rotor show the solid-state NMR characteristics of the individual polycrystalline metallocenes. The described formation of solid solutions of metallocenes in the absence of a solvent will open new pathways to homogeneously mixed nanoparticles with desired metal ratios and dual-atom catalysts.

Design of Redox-Active Cs⊂{Fe4Ni4} Cyanide-Bridged Cage Complexes Bearing Monodentate Ligands: Synthesis, Structure, and Electronic Properties

In recent years, strong efforts have been devoted to the design and crystallization of molecular models of the cyanido-bridged inorganic polymers known as “Prussian Blue Analogues” (PBA). In this work, we more specifically focus on soluble octametallic complexes that represent an elemental unit of the PBA cubic network. The self-assembly of tris-cyanido, the fac-[FeIII(Tp)(CN)3]− (Tp = hydro-tris(pyrazol-1-yl-borate) complex, and Ni(II) salts is shown to lead to {[Fe(Tp)(CN)3]4[Ni(S)3]4} procubes, where the Ni(II) ions are coordinated to labile solvent molecules (S: DMF or CH3CN). 1H and 133Cs paramagnetic NMR studies show that (i) the cubic complex is relatively stable during several days in solution, in particular in acetonitrile and (ii) a Cs+ ion can be inserted inside the cubic cavity as revealed by the presence of a strongly shifted 133Cs paramagnetic signal near −800 ppm at 300 K. The resulting Cs⊂{[Fe(Tp)(CN)3]4[Ni(S)3]4}5+ procube shows an enhanced stability as shown by time dependent 1H and 133Cs paramagnetic NMR spectra collected during several weeks. FT-IR spectra confirm the expected Fe(III) and Ni(II) redox states, with the occurrence of a single characteristic cyanide stretching vibration near 2170 cm–1. The Fe(III) redox state is also confirmed by cyclic voltammetry experiments in acetonitrile, with the occurrence of four pseudoreversible reduction events that can be assigned to the successive reduction of the FeIII ions in the Cs procube. Although these procubes could not be isolated as single crystals, the substitution of the labile coordinated solvent of the Cs-containing procube by N-donor imidazole monodentate ligands allows the crystallization of the novel Cs⊂{[Fe(Tp)(CN)3]4-[NiII(Im)3]4}Cl3 (Im = 1H imidazole) cubic complex by slow diffusion of ether into a DMF mother solution. The analyses of this cube demonstrate that in solution in ambient condition, Fe(III) centers are gradually reduced to Fe(II). The presence of three chlorides as counterions suggests that the cube can be isolated in the FeII2FeIII2NiII4 redox state. The presence of at least two Fe(II) ions is actually confirmed by cyclic voltammetry experiment in DMF and FT-IR spectroscopy. An intermediate state FeIIFeIII3NiII4 can be isolated by isolating fresh crystals (ca. 72 h) as demonstrated by FT-IR, cyclic voltammetry, and the magnetic measurements, that also reveal the presence of paramagnetic ferromagnetic interactions between the low-spin FeIII and NiII ions.

Comparison of through-space homonuclear correlations between quadrupolar nuclei in solids

Various two-dimensional (2D) homonuclear correlation experiments have been proposed to observe proximities between identical half-integer spin quadrupolar nuclei in solids. These experiments select either the single- or double-quantum coherences during the indirect evolution period, t1. We compare here the efficiency and the robustness of the 2D double-quantum to single-quantum (DQ-SQ) and SQ-SQ homonuclear correlations for two half-integer spin quadrupolar isotopes subject to small chemical shift anisotropy (CSA): 11B with a nuclear spin I = 3/2 and 27Al with I = 5/2. Such a comparison is performed using experiments on two model samples: Li2B4O7 for 11B and AlPO4-14 for 27Al. For both isotopes, the DQ-SQ homonuclear correlations are recommended since they allow probing the proximities between nuclei with close or identical frequencies. In the case of small or moderate isotropic chemical shift differences (e.g. 11B) the [SR221] or [BR221] bracketed DQ-SQ recoupling schemes are recommended; whereas it is the BR221 un-bracketed one otherwise (e.g. 27Al).

Optimization of experimental conditions for structural studies of the membrane surface complex between the small GTPase Arf1 and the ArfGAP ASAP1 by paramagnetic relaxation enhancement NMR.

Stimulated GTP hydrolysis of the small, membrane bound GTPase, Arf1, by the Arf GTPase activating protein (ArfGAP), ASAP1, participates in the regulation of actin-dependent membrane traffic and organelle structure. We previously showed that a functional complex between Arf1 (∼ 22 kDa) and the core catalytic domain of ASAP1—referred to as ASAP1-PZA (∼ 44 kDa) can be built at the membrane surface of a nanodisc (∼ 90 KDa). For a complex of that size, slow tumbling in solution and spectral crowding can hinder the collection of clear, high-quality NMR spectra. This study aims at optimizing sample preparation and experimental conditions to measure distances between MTSL- tagged Arf1 and isotopically labelled ASAP1-PZA at the membrane surface by paramagnetic relaxation enhancement (PRE) NMR. To minimize the size of the membrane bound complex, we developed conditions to obtain a stable, single Arf1:ASAP1 PZA complex per nanodisc and monitored results by analysis of protein band intensities on SDS-PAGE and SEC chromatography. Influence of temperature on protein stability and spectrum quality was monitored by recording Methyl-TROSY HMQC spectra of U-2H, 15N, ILV 13C methyl labeled Arf1. We show that optimized sample preparation and the use of ILV 13C segmentally methyl labeled PZA allow the collection of distance restraints between Arf1 and the individually labelled PH or ZA domain of ASAP1-PZA at the membrane surface.

The Q163C/Q309C mutant of αMI-domain is an active variant suitable for NMR characterization.

Integrin αMβ2 (Mac-1, CD11b/CD18, CR3) is an important adhesion receptor expressed on monocytes. Mac-1 is responsible for mediating cell migration, phagocytosis, degranulation as well as cell-cell fusion. It is also the most promiscuous integrin in terms of ligand specificity with over 100 ligands, most of which use the αMI-domain as their binding site. Despite the importance of αMI-domain in defining ligand interactions of Mac-1, structural studies of αMI-domain's interactions with ligands are lacking. In particular, solution NMR studies of αMI-domain's interaction with ligands have not been possible because the most commonly used active αMI-domain mutants (I316G and ΔK315) are not sufficiently stable and soluble to be used in solution NMR. The goal of this study is to identify an αMI-domain active mutant that's amenable to NMR characterization. By screening known activating mutations of αMI-domain, we determined that the Q163C/Q309C mutant, which converts the αMI-domain into its active form through the formation of an intramolecular disulfide bond, can be produced with a high yield and is more stable than other active mutants. In addition, the Q163C/Q309C mutant has better NMR spectral quality than other active mutants and its affinity for ligands is comparable to other active mutants. Analysis of the Co2+-induced pseudocontact shifts in the Q163C/Q309C mutant showed the structure of the mutant is consistent with the active conformation. Finally, we show that the minor fraction of the Q163C/Q309C mutant without the disulfide bond can be removed through the use of carboxymethyl sepharose chromatography. We think the availability of this mutant for NMR study will significantly enhance structural characterizations of αMI-domain-ligand interactions.

HECT domain interaction with ubiquitin binding sites on Tsg101-UEV controls HIV-1 egress, maturation, and infectivity

The HECT domain of HECT E3 ligases consists of flexibly linked N- and C-terminal lobes, with a ubiquitin (Ub) donor site on the C-lobe that is directly involved in substrate modification. HECT ligases also possess a secondary Ub binding site in the N-lobe, which is thought to play a role in processivity, specificity, or regulation. Here, we report the use of paramagnetic solution NMR to characterize a complex formed between the isolated HECT domain of neural precursor cell-expressed developmentally downregulated 4-1 and the ubiquitin E2 variant (UEV) domain of tumor susceptibility gene 101 (Tsg101). Both proteins are involved in endosomal trafficking, a process driven by Ub signaling, and are hijacked by viral pathogens for particle assembly; however, a direct interaction between them has not been described, and the mechanism by which the HECT E3 ligase contributes to pathogen formation has not been elucidated. We provide evidence for their association, consisting of multiple sites on the neural precursor cell-expressed developmentally downregulated 4-1 HECT domain and elements of the Tsg101 UEV domain involved in noncovalent ubiquitin binding. Furthermore, we show using an established reporter assay that HECT residues perturbed by UEV proximity define determinants of viral maturation and infectivity. These results suggest the UEV interaction is a determinant of HECT activity in Ub signaling. As the endosomal trafficking pathway is hijacked by several human pathogens for egress, the HECT-UEV interaction could represent a potential novel target for therapeutic intervention.

Effective assessment of lanthanide ion delivery into live cells by paramagnetic NMR spectroscopy.

We report an effective assessment of lanthanide ion (Ln3+) delivery into live cells by paramagnetic NMR spectroscopy. Free Ln3+ ions are toxic to live cells resulting in a gradual leakage of target proteins to the extracellular media. The citrate-Ln3+ complex is an efficient and mild reagent over the free Ln3+ form for live cell delivery.

A study across scales to unveil microstructural regimes in the multivalent metal driven self-assembly of cellulose nanocrystals.

Understanding the behaviour of self-assembled systems, from nanoscale building blocks to bulk materials, is a central theme for the rational design of high-performance materials. Herein, we revealed, at different length scales, how the self-assembly of TEMPO-oxidised cellulose nanocrystals (TOCNCs) into rod fractal gels is directed by the complexation of Fe3+ ions on the surface of colloidal particles. Different specificities in Fe3+ binding on the TOCNC surface and conformational changes of the nanocellulose chain were unveiled by paramagnetic NMR spectroscopy. The macroscopic properties of systems presenting different concentrations of TOCNCs and Fe3+ ions were investigated by rheology and microscopy, demonstrating the tunability of the self-assembly of cellulose nanorods driven by Fe3+ complexation. Near-atomistic coarse-grained molecular dynamics simulations were developed to gain microscopic insight into the behaviour of this colloidal system. We found that the formation of different self-assembled architectures is driven by metal-nanocellulose complexation combined with the attenuation of electrostatic repulsion and water structuration around cellulose, leading to different microstructural regimes, from isolated nanorods to disconnected rod fractal clusters and rod fractal gels. These findings lay the foundation to unlock the full potential of cellulose nanocrystals as sustainable building blocks to develop self-assembled materials with defined structural control for a range of advanced applications.

Numeric simulation of steel twin disc system under rolling-sliding contact

Various mechanical parts come into high-load rolling and sliding contact at the contact surface. Even with technological advancements, mechanical failures still occur. Rolling-sliding mechanical contact issues are the primary cause of over 90 % of surface and subsurface metallic failures and they are only becoming worse. Using discretised continuum 2D finite element methods (FEM), this research investigates the parametric contact effect of a steel twin disc system subjected to rolling-sliding contact at varied surface friction and comprehensive load condition. The equivalent von Mises stress distribution, contact pressure distribution and shift position of maximum subsurface stress on the contour region are all influenced by changes in compressive load and coefficient of friction, according to a numerical surface-to-surface contact simulation performed with Abaqus at mean Hertzian pressure. The maximal equivalent stress, for a given load, reaches a peak in the subsurface and moves farther away from the surface when the coefficient of friction decreases and comes close to the contact surface when the coefficient of friction increases. Consistency is shown by the analytical and numerical results.

NMR exchange dynamics studies of metal-capped cyclodextrins reveal multiple populations of host-guest complexes in solution.

Metal-capped molecular hosts are unique in supramolecular chemistry, benefitting from the inner cavity's hydrophobic nature and the metal center's electrochemical properties. It is shown here that the paramagnetic properties of the metals in lanthanide-capped cyclodextrins (Ln-α-CDs and Ln-β-CDs) are a convenient NMR indicator for different populations of host-guest complexes in a given solution. The paramagnetic guest exchange saturation transfer (paraGEST) method was used to study the exchange dynamics in systems composed of Ln-α-CDs or Ln-β-CDs with fluorinated guests, revealing multiple co-existing populations of host-guest complexes exclusively in solutions containing Ln-β-CDs. The enhanced spectral resolution of paraGEST, achieved by a strong pseudo contact shift induction, revealed that different molecular guests can adopt multiple orientations within Ln-β-CDs' cavities and, in contrast, only a single orientation inside Ln-α-CDs. Thus, paraGEST, which can significantly improve NMR detectability and spectral resolution of host-guest systems that experience fast exchange dynamics, is a convenient tool for studying supramolecular systems of metal-capped molecular hosts.

Theoretical (B3lyp) and Spectroscopic (Ft-Ir, 1h-Nmr and 13c-Nmr) Investigation of 2- Methoxy-6-[(3-(P-Methylbenzyl)-4,5-Dihydro-1h-1,2,4-Triazol-5-One-4-Yl)-Azomethin]-Phenyl Benzoate

Density functional theory (DFT) is an inexpensive approach used to study the molecular structure, many theoretical properties, biological activities and electronic properties of simple and complex compounds. In this study, the all quantum chemical studies of 2-Methoxy-6-[(3-(p-methylbenzyl)-4,5-dihydro-1H-1,2,4-triazol-5-one-4-yl)-azomethin]-phenyl Benzoate molecule were calculated using the DFT(B3LYP) method with 6-311++G(d,p) basis set. For use in all these computational processes, initially the molecule was optimized. Thus, the most stable state of atoms was reached. Then, the calculations of carbon-13 and proton-NMR isotropic shift values were performed in the solvent (DMSO) and gaseous with "the gauge-independent atomic orbital" (GIAO). Infrared (FT-IR) vibration frequency values were calculated from the Veda4f program. The theoretical vibration frequency values were compared with the experimental IR values. Experimental data obtained from the literature. In addition, the electronic properties (chemical hardness and softness, ionization potential (I), electronegativity (χ), electron affinity (A), electrophilic and nucleophilic index), ΔEg energy gap, HOMO-LUMO energies, the geometric properties (bond angle and length), the thermodynamic properties (thermal capacity (CV), entropy (S), thermal energy (E), dipole moment, mulliken atomic charge values, molecular electron potential (MEP), total density and contour surface maps and the total energy of the molecule were determined.

Experimentical and Gaussian Calculations of 3-Ethyl-4-(2-Benzenesulfonyloxy)-Benzylideneamino-4,5-Dihydro-1H-1,2,4-Triazol-5-One

3-Ethyl-4-(2-benzenesulfonyloxy)-benzylideneamino-4,5-dihydro-1H-1,2,4-triazol-5-one has been optimized using the DFT/B3LYP and B3PW91 methods with the 6-311G(d,p) basis set in the ground state. The vibrational (IR) frequencies, 1H and 13C NMR chemical shift values (in gas phase and in DMSO solvent), nonlinear optical properties (NLO), HOMO−LUMO analysis and molecular electrostatic potential surfaces of 3-Ethyl-4-(2-benzenesulfonyloxy)-benzylideneamino-4,5-dihydro-1H-1,2,4-triazol-5-one have been calculated using the DFT/B3LYP and DFT/B3PW91 methods with the 6-311G(d,p) basis set. IR absorption frequencies of titled molecule were calculated by same methods. Theoretically calculated IR data are multiplied with appropriate adjustment factors. The data obtained according to DFT/B3LYP and DFT/B3PW91 are formed using theoretical infrared spectrums. The veda4f program was used in defining IR data which were calculated data. 1H-NMR and 13C-NMR isotropic shift values were calculated by the method of GIAO using the program package Gaussian G09W. Experimental and theoretical values were inserted into the grafic according to equatation of δ exp=a+b. δ calc. The spectroscopic and structural data of titled molecule has been calculated by using 6-311G(d,p) basis set with DFT/B3LYP and DFT/B3PW9. The values obtained were compared with experimental values.

Formation of extramembrane β-strands controls dimerization of transmembrane helices in amyloid precursor protein C99

The 99-residue C-terminal domain of amyloid precursor protein (APP-C99), precursor to amyloid beta (Aβ), is a transmembrane (TM) protein containing intrinsically disordered N- and C-terminal extramembrane domains. Using molecular dynamics (MD) simulations, we show that the structural ensemble of the C99 monomer is best described in terms of thousands of states. The C99 monomer has a propensity to form β-strand in the C-terminal extramembrane domain, which explains the slow spin relaxation times observed in paramagnetic probe NMR experiments. Surprisingly, homodimerization of C99 not only narrows the conformational ensemble from thousands to a few states through the formation of metastable β-strands in extramembrane domains but also stabilizes extramembrane α-helices. The extramembrane domain structure is observed to dramatically impact the homodimerization motif, resulting in the modification of TM domain conformations. Our study provides an atomic-level structural basis for communication between the extramembrane domains of the C99 protein and TM homodimer formation. This finding could serve as a general model for understanding the influence of disordered extramembrane domains on TM protein structure.

Synthesis, crystal structure and 19F NMR parameters modelling of CaTiF6(H2O)2 yielding to a revision of the bond-valence parameters for the Ti4+/F− ion pair

CaTiF6(H2O)2 was synthetized by a solvothermal method and was found to be isostructural to SrTiF6⋅2H2O. The structure, refined from Powder X-Ray Diffraction (PXRD) data, is built from the connectivity of dimers [Ca2F10(H2O)4] of square antiprisms (SAP) [CaF5(H2O)3] and TiF6 octahedra. To assign the six 19F NMR resonances to the six fluorine crystallographic sites of same multiplicity, 19F magnetic shielding tensors have been calculated using the GIPAW method. Unusually, the plot of the experimental 19F isotropic chemical shift (δiso) values, as a function of the calculated 19F isotropic shielding (σiso) values, shows a much better alignment for the experimental structure than for the DFT-optimized one. Whereas, the dynamics of the structural water molecules under experimental conditions are not captured by the optimized structure, the experimental averaged structure provides a good account of the experimental data and a reliable assignment of the 19F resonances to the F sites. Finally, the previously established bond-valence (BV) parameter Rij for the Ti4+/F− ion pair (1.76 ​Å) leads to overestimated BV sum values for Ti. This trend has been observed for almost all other fluorotitanates. We then undertook to refine its value, using the Ti–F bond lengths from 70 carefully selected structures containing 134 Ti sites forming TiF6 octahedra, and leading to Rij ​= ​1.706 ​Å.

Mononuclear/Binuclear [VIVO]/[VVO2] Complexes Derived from 1,3-Diaminoguanidine and Their Catalytic Application for the Oxidation of Benzoin via Oxygen Atom Transfer.

Ligands H4sal-dag (I) and H4Brsal-dag (II) derived from 1,3-diaminoguanidine and salicylaldehyde or 5-bromosalicylaldehyde react with one or 2 mol equivalent of vanadium precursor to give two different series of vanadium complexes. Thus, complexes [VIVO(H2sal-dag) (H2O)] (1) and [VIVO(H2Brsal-dag) (H2O)] (2) were isolated by the reaction of an equimolar ratio of these ligands with [VIVO(acac)2] in MeOH. In the presence of K+/Cs+ ion and using aerially oxidized [VIVO(acac)2], the above reaction gave complexes [K(H2O){VVO2(H2sal-dag)}]2 (3), [Cs(H2O){VVO2(H2sal-dag)}]2 (4), [K(H2O){VO2(H2Brsal-dag)}]2 (5), and [Cs(H2O){VVO2(H2Brsal-dag)}]2 (6), which could also be isolated by direct aerial oxidation of complexes 1 and 2 in MeOH in the presence of K+/Cs+ ion. Complexes [(H2O)VIVO(Hsal-dag)VVO2] (7) and [(H2O)VIVO(HBrsal-dag)VVO2] (8) were isolated upon increasing the ligand-to-vanadium precursor molar ratio to 1:2 under an air atmosphere. When I and II were reacted with aerially oxidized [VIVO(acac)2] in a 1:2 molar ratio in MeOH in the presence of K+/Cs+ ion, they formed [K(H2O)5{(VVO2)2(Hsal-dag)}]2 (9), [Cs(H2O)2{(VVO2)2(Hsal-dag)}]2 (10), [K2(H2O)4{(VVO2)2(Brsal-dag)}]2 (11), and [Cs2(H2O)4{(VVO2)2(Brsal-dag)}]2 (12). The structures of complexes 3, 4, 5, and 9 determined by single-crystal X-ray diffraction study confirm the mono-, bi-, tri-, and tetra-anionic behaviors of the ligands. All complexes were found to be an effective catalyst for the oxidation of benzoin to benzil via oxygen atom transfer (OAT) between DMSO and benzoin. Under aerobic condition, this oxidation also proceeds effectively in the absence of DMSO. Electron paramagnetic resonance and 51V NMR studies demonstrated the active role of a stable V(IV) intermediate during OAT between DMSO and benzoin.

Quantum chemical study of effect on adsorption properties of antituberculosis drug N-Cyclopentylidenepyridine-4-carbohydrazide interaction with CNT(C56H16)

Tuberculosis is the most common disease that affects the lungs in humans. The electronic structural and chemical properties of the antituberculosis drug N-Cyclopentylidenepyridine-4-carbohydrazide have already been investigated. The adsorption properties of the antituberculosis drug N-Cyclopentylidenepyridine-4-carbohydrazide (CPPC) with single-wall carbon nanotube CNT(C56H16) are investigated using a combination of DFT/B3LYP method and 6-31G(d,p) basis set in both gaseous and water solvent, and calculated results are compared. By comparing CNT's corresponding optimized bond lengths with CNT@CPPC, the effect of CPPC adsorption on optimized drug delivery system parameters has been discussed. Based on topological parameters, the nonbonding interaction between CNT and CPPC drug is discussed using QTAIM analysis at BCP in both gas and water solvent. The thermodynamical stability of the CPPC@CNT adsorption process is also calculated, showing the adsorption of CPPC with CNT favors in both media. Natural bond analysis (NBO) was used to investigate the IR spectra, and the effect of charge transfer from CPPC to CNT in CNT@CPPC in both media provides information about how polarity changes from gas to water solvent. Because drug delivery action is done in blood plasma, the UV–Vis spectra of CNT are compared to CNT@CPPC in water solvent, providing insight into the adsorption of CPPC drug by CNT. We have compared the chemical shift isotropic (CS1) and chemical shift anisotropic (CSA) of CNT, CPPC, and CNT@CPPC to determine the change in electron density.

Theoretical and Experimental Study on Molecular Docking, Spectral and Electronic Properties of N,N-Bis (Salysylaldehyde-2,3-Diamino-1-Propanol) Nanostructure

In this study, theoretical and experimental properties (Structural, Spectral and Electronic Properties) and molecular docking of N,N- bis (salysylaldehyde-2,3- Diamino-1-propanol) molecule were studied. Timedependent density functional theory (TDDFT) and density functional theory (DFT) are employed for the theoritcal calculation. The composite's spectroscopic surveys were conducted using Proton nuclear magnetic resonance, FT-IR and UV/Vis spectroscopy techniques. The 1H NMR spectra for proton nuclear magnetic resonance have been examined with DMSO4 solvent. The FT-IR spectrum in rigid situation has been calculated to be between 4000-400 cm-1. The absorption spectra intensity of the composite with ethanol has been calculated to be between 200 and 800 nm. Scanning electron microscope (SEM) image has been study. Results demonstrated that the compound scanning electron microscopy image resembled a sphericals with particle size of 50 nm. The data structure, vibrational central modes, UV/V spectrum with 1H NMR isotropic chemical shifts of this molecule in the ground state were assessed utilizing the theory of functional density (thus DFT) and the B3LYP/6- 311G(d,p) basis group. The energies of reorganization for the hole and the electron have also been calculated. Finally, the assessment between the data of experiment and the results that have been calculated showed a good agreement. The inhibitory potential of the investigated compound was assessed against the protein PBP1 bacteria in a molecular docking. The chemical's carbonyl group was demonstrated to show a substantial role in antibacterial application; out of seven contacts, the carbonyl group made five bonds with the bacteria's main protein (Van der Waals bond and four good hydrogen bonds). This high bind energy was computed (-6.9 kcal/mol) indicating considerable antibacterial action.