Chemical Shift Values Research Articles

Crystal structure, vibrational spectroscopy, 1H NMR, and DFT analyses with antibacterial activity studies on silver nitrate complex of 5-iodoindole

A novel complex silver nitrate of 5-iodindole molecule has been synthesized and characterized by single-crystal X-ray diffraction, infrared and Raman spectroscopy, and 1H NMR analysis. DFT calculations were performed using the B3LYP with 6–311++G(d,p) basis set for light atoms (C,H, N, and O) and the DGDZVP basis set for heavy atoms (Ag and I). Theoretical and experimental bond lengths and bond angles have been compared and determined to be in good agreement with each other. By using 1H NMR analysis, the chemical shift values of H atoms in this new structure were determined and compared with the theoretically calculated values. Also, experimental FT-IR and FT-Raman modes of the complex structure assigned that depending on total energy distribution (TED) values have been compared with theoretical wavenumbers. The HOMO-LUMO energy gap, the frontier molecular orbital, the molecular electrostatic potential map, and atomic charge analysis have been carried out to reveal the electronic properties of the structure. The non-linear optical properties of the title molecule and its thermodynamic properties such as entropy, heat capacity, enthalpy change, and Gibbs free energy at different temperatures were investigated. Finally, the antibacterial activity of this new structure obtained from the synthesis of 5-iodoindole with silver nitrate has been evaluated.

1H, 15N and 13C resonance assignments of a minimal CPSF73-CPSF100 C-terminal heterodimer.

The initial pre-mRNA transcript in eukaryotes is processed by a large multi-protein complex in order to correctly cleave the 3' end, and to subsequently add the polyadenosine tail. This cleavage and polyadenylation specificity factor (CPSF) is composed of separate subunits, with structural information available for both isolated subunits and also larger assembled complexes. Nevertheless, certain key components of CPSF still lack high-resolution atomic data. One such region is the heterodimer formed between the first and second C-terminal domains of the endonuclease CPSF73, with those from the catalytically inactive CPSF100. Here we report the backbone and sidechain resonance assignments of a minimal C-terminal heterodimer of CPSF73-CPSF100 derived from the parasite Encephalitozoon cuniculi. The assignment process used several amino-acid specific labeling strategies, and the chemical shift values allow for secondary structure prediction.

The Effect of Hydrogenation on the Contest between Aromaticity and Antiaromaticity in Norcorrole.

Magnetic shielding studies demonstrate that successive hydrogenation of NiII norcorrole (NiNc), a stable molecule combining aromatic and antiaromatic features, first weakens and then eliminates the central antiaromatic region, even though the NiNc antiaromatic "core", a 14-membered conjugated cycle with 16 π electrons, is formally preserved throughout the H2 NiNc-H8 NiNc series. The differences between aromatic and non-aromatic isotropic shielding distributions and nucleus-independent chemical shift (NICS) values in these hydrogenated porphyrin analogues are highlighted by comparing the results for the members of the H2 NiNc-H8 NiNc series to those for the aromatic NiII porphyrin complex. The results strongly support the unexpected and counterintuitive conclusion that H8 NiNc will be nonaromatic, without even a trace of antiaromaticity. Based on these findings, H8 NiNc is predicted to be the most stable member of the H2 NiNc-H8 NiNc series.

Diazoxide and its Tautomers - A DFT Treatment

Diazoxide have several potential effectors that may potentially contribute to cardio protection. It is used to manage symptoms of hypoglycemia that is caused by pancreas cancer, surgery, or other conditions. It also acts as a non-diuretic antihypertensive agent. Diazoxide possessing various tautomeric forms should display variable biological properties depending on its tautomer content. It may exhibit 1,3- and 1,5-type proton tautomerism. Presently, all those possible tautomeric forms are considered. All the calculations have been performed within the realm of density functional theory with the constraints of B3LYP/6-311++G(d,p) level. All the tautomers are electronically stable and thermo chemically favorable formation values at the standard conditions. Some quantum chemical and spectral properties of those tautomeric systems as well as nucleus-independent chemical shift (NICS) values have been obtained and discussed.

Interaction of Isonicotinic Acid Hydrazide with Carboxylic Acid Anhydrides

There has been presented data on the synthesis of monoamides and cyclic imides which are derivatives of isonicotinic acid hydrazide. Cyclic anhydrides of carboxylic acids (succinic, maleic and phthalic) easily react with the hydrazide of isonicotinic acid with cycle opening, forming isonicotinoylhydrazide of dicarboxylic acids, and under more severe conditions the latter are transformed into cyclic acid imides. The structures of the synthesized compounds were studied using 1H- and 13C-NMR spectroscopy, as well as data from twodimensional COSY (1H-1H) and HMQC (1H-13C) spectra. The values of chemical shifts, multiplicity and integral intensity of 1H and 13C signals in one-dimensional NMR spectra were determined. Homo- and heteronuclear interactions confirming the structure of the studied compounds were established using spectra in the COSY (1H-1H) and HMQC (1H-13C) formats. In the approximation of the density functional B3LYP with a base set of 6-31G(d), the enthalpy of the reactions ΔHr in the absence and in the presence of a solvent — isopropanol (self-consistent reaction field method) were calculated quantum-chemically

THERMAL STABILITY AND THERMODYNAMICS OF PYROLYSIS OF MONO-, BI-, AND TRINUCLEAR CARBINOL DERIVATIVES OF FERROCENE

Mono-, bi- and trinuclear carbinol derivatives of ferrocene C5H5FeC5H4-C(CH3)2OH (I), [C5H5FeC5H4]2C(CH3)OH (II), [C5H5FeC5H4]3C-OH (III) were synthesized. the thermal stability and thermodynamics of the pyrolysis of these compounds have been studied. The composition and structure of the synthesized compounds were established by elemental analysis (AAS, C, H analysis), 1H NMR, IR, and UV/visible spectroscopy. In the IR spectra of these compounds there are absorption bands with ν(OH) =2910-3040 cm-1 and ν(OH) = 3080-3190 cm-1 , and in the 1H NMR spectra there are absorption bands with chemical shift values δ(OH) = 4.29-4.18 ppm for OH groups that differ in position and are due to the formation of intra- and intermolecular associates with the participation of OH groups. The electronic absorption spectra indicate the presence of characteristic absorption bands in compounds I-III at λmax = 270 (I), 278 (II), and 285 nm (III). It is shown that when samples are heated from room temperature to 700 °C in an inert gas flow, the residual mass of compounds I-III is 2.05, 20.24, and 66.96% of the initial mass, respectively, and these compounds decompose to form nanosized iron particles. /iron oxide and carbon. The values of the melting temperature and saturation magnetization of nanosized iron particles formed during the pyrolysis of ferrocene and its derivatives I-III are calculated.

Rapid prediction of full spin systems using uncertainty-aware machine learning.

Accurate simulation of solution NMR spectra requires knowledge of all chemical shift and scalar coupling parameters, traditionally accomplished by heuristic-based techniques or ab initio computational chemistry methods. Here we present a novel machine learning technique which combines uncertainty-aware deep learning with rapid estimates of conformational geometries to generate Full Spin System Predictions with UnCertainty (FullSSPrUCe). We improve on previous state of the art in accuracy on chemical shift values, predicting protons to within 0.209 ppm and carbons to within 1.213 ppm. Further, we are able to predict all scalar coupling values, unlike previous GNN models, achieving 3JHH accuracies between 0.838 Hz and 1.392 Hz on small experimental datasets. Our uncertainty quantification shows a strong, useful correlation with accuracy, with the most confident predictions having significantly reduced error, including our top-80% most confident proton shift predictions having an average error of only 0.140 ppm. We also properly handle stereoisomerism and intelligently augment experimental data with ab initio data through disagreement regularization to account for deficiencies in training data.

TD-DFT calculations, dipole moments, and solvatochromic properties of 2-aminochromone-3-carboxaldehyde and its hydrazone derivatives.

2-Aminochromone-3-carboxaldehyde (ACC) and its hydrazones (ACMHCA and ACMNPHTCA) with semicarbazide hydrochloride and N-phenylthiosemicarbazide were synthesized and characterized by elemental analysis and spectral studies. The solvatochromic behavior of the title compounds in various solvents showed distinct bathochromic shifts on going from nonpolar to polar solvents, suggesting intramolecular-charge-transfer (ICT) solute-solvent interactions. The ground and excited state dipole moments of ACC, ACMHCA, and ACMNPHTCA were determined experimentally by the solvatochromic shift method using the Bilot-Kawski, Lippert-Mataga, Bakhshiev, Kawski-Chamma-Viallet functions, and a microscopic Reichardt's solvent polarity parameter (ENT). All the investigated molecules showed a substantial increase in the dipole moment upon excitation to the emitting state. The experimental results were generally consistent with the values obtained by the TD-DFT, B3LYP/6-311G++(d,p) method. Molecular electrostatic potential (MEP) mapping and natural charge and natural bonding orbital (NBO) analysis were performed and the results were discussed. The 1H NMR chemical shifts of the prepared compounds were simulated by the gage independent atomic orbital (GIAO) method and compared with their experimental chemical shift values. The biological activity data were correlated with the frontier molecular orbitals. The photovoltaic behavior of the title compounds showed there was sufficient electron injection.

Development of non-toxic and water-soluble nanofibers from oseltamivir in the presence of cyclodextrins for drug release

β-Cyclodextrin (BCD) and its derivative, Hydroxypropyl-β-Cyclodextrin (HCD) are cyclic oligosaccharides that present the ability to form inclusion complexes (ICs) with hydrophobic molecules and can bring new functionalities to a wide range of materials. As part of this study, water-soluble electrospun nanofibers (NFs) of oseltamivir (OTV) are tested using a variety of protocols in combination with native and its derivatives. There are some limitations to the use of oseltamivir (OTV), an antiviral drug with medium solubility in water. To improve the physical and chemical properties of OTV, β-cyclodextrin:oseltamivir inclusion complexes (OTV:BCD-ICs) and hydroxypropyl-β-cyclodextrin:oseltamivir inclusion complexes (OTV:HCD-ICs) with polyvinyl alcohol mediated nanofibers (OTV:BCD-ICs/PVA NFs, and OTV:HCD-ICs/PVA NFs) are fabricated via electrospinning. ICs are confirmed using several analytical techniques. There are a changes in the chemical shift values after the OTV molecule is introduced into the cavity of both the CDs on the surface of NFs. As shown by scanning electron microscopic images, NFs are homogeneous and particle-free. An analysis of thermogravimetric data indicated that OTV is thermostable after IC formation. Additionally, XPS analysis confirmed the presence of ICs on the surface of NFs. NFs containing OTV:BCD-ICs/PVA had a sustained release of OTV in comparison with NFs containing free material. Based on the dissolution study, the material obtained has no toxic properties and is easily water-soluble. As a result of the fabrication of NFs, OTV is released more rapidly, thus leading to the development of NFs that are non-toxic and water-soluble for creating drug delivery systems.

A Cleavable Self-Inclusion Conjugate with Enhanced Biocompatibility and Antitumor Bioactivity

A Cleavable Self-Inclusion Conjugate with Enhanced Biocompatibility and Antitumor Bioactivity

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.

Experimental (Ft-Ir, 13c/ 1h-Nmr) and Dft Studies of 3-(P-Methylbenzyl)-4-(4-Methylthiobenzylidenamino-4,5-Dihydro-1h-1,2,4-Triazol-5-One

The 3-(p-Methylbenzyl)-4-(4-methylthiobenzylidenamino-4,5-dihydro-1H-1,2,4-triazol-5-one Schiff base was synthesized for investigated some theoretical properties. Firstly, the molecule was optimized with density functional theory (DFT) method and at the 6-311++G(d,p) basis set of Gaussian 09 program. From the optimized geometry of the molecule, the highest occupied molecular orbital (HOMO) and the lowest unoccupied molecular orbital (LUMO) energy and thermodynamics properties (heat capacity CV0, entropy S0 and enthalpy H0), electronic calculations (global hardness (η), electron affinity (A), electronegativity (χ), ionization potential (I), softness (σ)), dipole moments, bond lengths, bond angles, the mulliken charges, the molecular surface maps (molecular electrostatic potential (MEP), the electron density, MEP contour and the total density), the energy gap (ΔEgap = ELUMO-EHOMO), IR vibrational frequency, the electric dipole moment, the static polarizability (α) and the static first-order hyperpolarizability (β) values were calculated with B3LYP/ 6-311++G (d, p). Finally, the 1H NMR and 13C-NMR chemical shift values was calculated with gauge independent atomic orbital (GIAO) method. All theoretical spectral data were compared with experimental data obtained from the literature and regression analysis graphs were drawn.

Quantum Chemical Calculations of 3-Benzyl-4-(3-Ethoxy-2-(4-Toluenesulfonlyoxy)-Benzlyideneamino]-4,5-Dihydro-1H-1,2,4-Triazol-5-One

In this study, 3-Benzyl-4-(3-ethoxy-2-(4-toluenesulfonlyoxy)-benzlyideneamino]-4,5-dihydro-1H-1,2,4-triazol-5-one was theoretically investigated. Initialy, the molecule was optimized by using DFT(B3LYP)/6-31G(d, p) basis set. The molecule’s structural parameters (dihedral angles, bond lengths and bond angles), HOMO (the highest occupied molecular orbital) and LUMO (the lowest unoccupied molecular orbital) energies, vibrational frequencies, thermodynamic and electronic properties (thermal capacity , rotation constants, entropy , total energy, electronegativity, electron affinity, chemical softness and hardness), the energy gap (ΔEgap = ELUMO-EHOMO), mulliken atomic charges, the surface maps were calculated by using Gaussian09W program. 13C- NMR and 1H-NMR chemical shift values of molecule also were calculated by GIAO. In additon, theoretical infrared (IR) vibration frequencies values which were scaled with certain scala factor were obtained using the veda4f program. Infrared spectra of molecul were formed according to obtained these values. The all spectroscopic and structural data of compounds were calculated by using 6-31G(d, p) basis set with density functional method (DFT/B3LYP) and compared with experimental values.

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.

Crystal structure, IR and NMR spectra of (E)-2‑methoxy-4-(2-morpholinovinyl)phenol molecule and its DFT calculations

In this study; molecular structure, IR and NMR spectroscopic properties of (E)-2‑methoxy-4-(2-morpholinovinyl)phenol are investigated both experimentally and theoretically for the first time. The structural characterization of the compound was carried out by X-ray diffraction technique. The bond lengths, bond angles and dihedral angles of the compound were optimized using DFT with the B3LYP 6–311G(dp) base set. Using the optimized results, the infrared vibration frequencies and intensities of the compound as well as the 1H and 13C chemical shift values in the NMR spectrum were calculated with the B3LYP 6–311G(dp) basis set. In addition, the potential energy distributions (PED) of the structure were calculated to determine some characteristic vibrational frequencies of the compound. It is found that the theoretically calculated data support the experimental results. As a result, there is a good agreement between the experimentally determined structural parameters, vibrational frequencies, chemical shifts and theoretically calculated data of the compound.

Synthesis and Theoretical Calculations of Benzoic Acid-Based New Mono Azo Dye

This study describes the synthesis, characterization and theoretical calculation of 3,5-dihydroxy-2-(naphthalen-2-yldiazenyl) benzoic acid. The synthesized compound was obtained through efficient synthetic route using 2-Naphthylamine and 3,5-dihydroxybenzoic acid as starting materials and characterized by various spectroscopic techniques such as Fouirer Transform Infrared Spectroscopy (FTIR), Proton Nuclear Magnetic Resonance Spectroscopy (1H-NMR), Carbon Nuclear Magnetic Resonance Spectroscopy (13C-NMR), Ultraviolet–visible spectroscopy (UV-Vis). All theoretical calculation was performed with Density Functional Theory (DFT). Optimized molecular structure, vibrational spectra, NMR chemical shift values, frontier molecular orbitals, bond lengths (Å), bond angles (°) and Molecular Electrostatic Potential (MEP) diagram of molecule were calculated using the 6-311G(d,p) basis set. It has been observed that the results obtained from the experimental and theoretical calculations support each other and were in harmony.

Calculation of the Chemical Shift of N-15 by Quantum Mechanics

This study aims to develop a new set of added variables to calculate the chemical shift N-15 based on quantum mechanics methods for a number of periodic compounds using theoretical chemistry (Gaussian V.12, 2010). The relationship between the experimental N-15 was conducted with two mechanical variables, such as SPSS V 2019. The relationship between the theoretical chemical shift values ​​of the N-15 atom nucleus and practical values ​​in literature was examined. Two quantitative mechanical methods are used to extract information to calculate the N-15 chemical shift, the traditional method, the other AB Initio method, and the DFT job theory. The success of the method is determined in terms of the values ​​of the correlation coefficient (R) and the standard error (SE), as well as the material meaning of the specified variables. A good consensus is seen between practical and theoretical values. A comparison was made between the two methods to find out the best in the chemical transformation account. The DFT method gave better results.

Quantum chemical, spectroscopic and molecular docking investigations of potential pulmonary fibrosis drug methyl 2-chloro 4-iodonicotinate.

In this work, the methyl 2-chloro 4-iodonicotinate (MCIN) was investigated to study the structural, spectroscopic and electronic properties using density functional theory (DFT) quantum chemical calculations. The most stable structure of MCIN was optimized by DFT/B3LYP method with a LanLD2Z basis set. The optimized parameters and vibrational wavenumbers were determined. The vibrational task of the molecule was done by potential energy distribution calculations. The 13 C NMR spectrum of the MCIN molecule was simulated by the Gauge-Invariant-Atomic Orbital method using a dimethyl sulfoxide solution and the isotropic chemical shift values of the molecule were calculated and observed. Ultraviolet-visible spectra were simulated and observed. The pharmaceutical activity was predicted using frontier molecular orbital and natural bond orbital analysis. The reactive sites of the MCIN molecule were determined using Mulliken atomic charge distribution, molecular electrostatic potential surface and the local reactivity analysis. The molecular docking analysis confirms that the title molecule can be used in drug design for the treatment of pulmonary fibrosis.

Chemical Shifts of Artificial Monomers Used to Construct Heterogeneous-Backbone Protein Mimetics in Random Coil and Folded States.

The construction of protein-sized synthetic chains that blend natural amino acids with artificial monomers to create so-called heterogeneous-backbones is a powerful approach to generate complex folds and functions from bio-inspired agents. A variety of techniques from structural biology commonly used to study natural proteins have been adapted to investigate folding in these entities. In NMR characterization of proteins, proton chemical shift is a straightforward to acquire, information-rich metric that bears directly on a variety of properties related to folding. Leveraging chemical shift to gain insight into folding requires a set of reference chemical shift values corresponding to each building block type (i.e., the 20 canonical amino acids in the case of natural proteins) in a random coil state and knowledge of systematic changes in chemical shift associated with particular folded conformations. Although well documented for natural proteins, these issues remain unexplored in the context of protein mimetics. Here, we report random coil chemical shift values for a library of artificial amino acid monomers frequently used to construct heterogeneous-backbone protein analogues as well as a spectroscopic signature associated with one monomer class, β3-residues bearing proteinogenic side chains, adopting a helical folded conformation. Collectively, these results will facilitate the continued utilization of NMR for the study of structure and dynamics in protein-like artificial backbones.

Antifungal diterpene from Rhizome of wild bornean ginger, Hornstedtia havilandii (Zingiberaceae)

Hornstedtia havilandii (K. Schum.) belongs to the ginger (Zingiberaceae) family and is one of the nine reported species of Hornstedtia in Borneo. It is widely used as an important resource in traditional healing and cultural practices by the tribal communities. Rhizome of H. havilandii was extracted in ethanol and its biologically active antifungal metabolite was isolated via bioassay-guided separation technique. Isolated compound was subjected to spectroscopy measurements and the structure was elucidated as (E)-labda-8(17),12-diene-15,16-dial (1). Although 1 was identified as a previously published compound, we were able to differentiate and assign the chemical shift values for two overlapping carbons; C-4 and C-18 via Gaussian processing of the 13C-NMR data, and consequent 2D NMR assignments. The antifungal activities were seen against crustacean pathogenic fungal strains Lagenidium thermophilum, Haliphthoros sabahensis, and Haliphthoros milfordensis as MIC value of <82.78 μM (25 μg/mL) while Fusarium solani and Fusarium oxysporum required <165.56 μM (50 μg/mL). In addition, this is the first record of H. havilandii that produces labdane type diterpene. Data revealed here could be used as an important chemotaxonomic marker for this genus.