13C NMR Chemical Shift Values Research Articles

Solvent effects on spectroscopic, electronic, and topological analyses, Hirshfeld surface, ADME, and molecular docking studies on antiviral pyridine carboxamide derivatives

A theoretical study of three pyridine carboxamide derivatives in conjunction with the Density Functional Theory (DFT) approach at the 6-311+G(d,p) basis set is presented along with X-ray results. The pyridine carboxamide derivatives were analyzed with the help of FT-IR, UV–Vis, 1H and 13C NMR investigation. The spectral characterizations were made by vibrational energy distribution analysis (VEDA4), which helps to assign vibrational frequencies to specific molecular vibrations. A comparative analysis of computed 1H and 13C NMR chemical shift values with experimental chemical shifts for the pyridine carboxamide compounds by applying the gauge-including atomic orbitals method in chloroform and acetone solvents was carried out. UV–Vis spectroscopy and electronic transitions were conducted on both chloroform and acetone solvents through the assistance of the TD-DFT methodology. Hirshfeld Surface analysis was employed to analyze the intermolecular hydrogen bonds of the type N-H⋯N to the crystal packing. The chemical properties of frontier molecular orbital and global reactivity descriptors were analyzed for the different solvents such as chloroform and acetone. The Fukui functions were used to identify reactive sites in a molecule, including those susceptible to nucleophilic and electrophilic outbreaks. The weak interactions were analyzed using reduced density gradient (RDG) analysis, a computational method used to study noncovalent interactions, including hydrogen bonding. The Absorption, Distribution, Metabolism, and Excretion (ADME) attributes of the studied compounds have been evaluated for drug discovery initiatives. Molecular docking studies with antiviral SARS-CoV-2 Mpro and Omicron variant containing the Q493R mutation proteins of three pyridine carboxamide derivatives (L3–L5) have been performed, and L5 has maximum binding energy values of −7.13 kcal/mol for 6LU7.

Quantum Chemical and Biological Properties of Coumarin Derivative Compound

This work presents the characterization of 8-t-buthyl-4-methyl-2H- chromen 2-one by quantum chemical calculations and spectral techniques. The molecular geometry, vibrational frequencies and gauge including atomic orbital (GIAO) 1H and 13C NMR chemical shift values of title compound in the ground state have been calculated using the density functional method (B3LYP) with the 6-31G(d) basis set. The theoretical vibrational frequencies and chemical shift values show good agreement with experimental values. In addition, DFT calculations of molecular electrostatic potentials and frontier molecular orbitals of the title were carried out at the B3LYP/6-31G(d) level of theory. The title compound was screened for antibacterial, antifungal and antioxidant activities.

Linking quinoline ring to 5-nitrofuran moiety via sulfonyl hydrazone bridge: Synthesis, structural characterization, DFT studies, and evaluation of antibacterial and antifungal activity

In the present work, we report the synthesis, structural characterization, and computational studies of (E)-N'-((5-nitrofuran-2-yl)methylene)quinoline-8-sulfonohydrazide (QNF) as a potential antimicrobial drug candidate. To design the target molecule, we utilized a molecular hybridization technique that connects two antimicrobial pharmacophores (quinoline and 5-nitrofuran rings) with a sulfonyl hydrazone moiety. QNF was synthesized by the condensation of quinoline-8-sulfonohydrazide with 5-nitrofuran-2-carbaldehyde, and characterized by various spectral techniques including single-crystal X-ray crystallography. QNF was extensively evaluated for its antibacterial and antifungal activity. The inhibition capacity of QNF on Candida albicans filamentation and biofilm formation was further investigated. Biofilm inhibition of QNF against C. albicans was supported by molecular docking studies in the binding site of agglutinin-like sequence 3 (Als3). Drug-like profile of QNF was confirmed by in silico calculation of its significant physicochemical properties. Additionally, the optimized geometrical structure, natural bond orbital calculations, frontier molecular orbital and molecular electrostatic potential analysis of QNF were carried out using the density functional theory method at the B3LYP with 6–31+G(d,p) basis set. The predictions of 1H and 13C NMR chemical shift values were performed using the gauge-independent atomic orbital method. Structural parameters and NMR values obtained experimentally were compared with the calculated values.

Nucleophilic reactions with the novel 7-(chromon-3-yl)quinolino [3′,4′:5,6] pyrano[3,2-c]quinoline: Synthesis, biological and computational studies

Condensation reaction of 3-formylchromone (1) with 1-ethyl-4-hydroxyquinolin-2(1H)-one (2) in glacial acetic acid afforded the condensation product 4; in 1:2 molar ratio. Compound 4 was used as precursor for construction of some propenones linked pentacyclic quinolinopyranoquinoline. Ring opening of chromone moiety in compound 4 was achieved via reactions with a diversity of primary amines leading to propenone derivatives 5–7 and 11–13 in good yields (62–73%). All propanone derivatives exist in the E-configuration as deduced from their 1H NMR spectra. DFT/B3LYP functional was used with 6–311+G(d,p) basis sets for all theoretical calculations. Based on optimized geometry, the chemical potential (Pi), electronegativity (χ), hardness (η) and electrophilicity index (ω) are some of the global reactivity descriptors that were computed to predict the chemical reactivity of the studied compounds; where compound 13 has the highest softness and electrophilicity index (ω). Moreover, to determine the relative stability of compounds 1–4, the thermodynamic parameters such as enthalpy and free energies of the reactions were computed; where compound 4 has the lowest free energy of reaction (-439.61 kcal/mol), so its formation is spontaneous. By utilizing molecular electrostatic potential (MEP) and local-based descriptors in the form of condensed Fukui functions of the starting compound 4, the susceptible sites for electrophilic and nucleophilic attack were investigated. For compound 4, fk+ and Δfk values are more positive at C9 and C7 than other sites and these sites have more electrophilic characters. Therefore, nucleophilic attacks began at C9. On the other hand, the GIAO approximation was used to compute the 1H and 13C NMR chemical shift values in the ground state, of the present compounds, where a good agreement was observed between experimental and theoretical chemical shift results. Further, the calculated first hyperpolarizability of prepared compounds are found to be greater than that of urea. So, these compounds are ideal candidates for non-linear optical applications. The synthesized compounds were screened for their antimicrobial and anticancer activities showing variable inhibitory action. Compounds 5, 7 and 13 were more effective antimicrobial candidates against all tested microorganisms, while compound 13 was the most active against HepG-2 cell lines. Furthermore, a quantitative structure–activity relationship (QSAR) (relationship between DFT calculated descriptors and biological activities pIC50) model was built by applying multiple linear regression (MLR) on the synthesized compounds as anticancer agents. Moreover, Lipinski's rule of five indicates no problems with oral bioavailability of the prepared compounds.

Spectroscopic investigations, quantum chemical, drug likeness and molecular docking studies of methyl 1-methyl-4-nitro-pyrrole-2-carboxylate: A novel ovarian cancer drug

Density functional theory (DFT) calculation was used to analyse the structural and vibrational properties of Methyl 1-Methyl-4-nitro-pyrrole-2-carboxylate (MMNPC) using the cc-pVTZ basis set. The potential energy surface scan and the most stable molecular structure were optimized using Gaussian 09 program. A potential energy distribution calculation was used to calculate and assign vibrational frequencies using the VEDA 4.0 program package. The Frontier Molecular Orbitals (FMOs) were analysed to determine their related molecular properties. Ab initio density functional theory (B3LYP/cc-pVTZ) method with basis set was used to calculate 13C NMR chemical shift values of MMNPC in the ground state. Fukui function and molecular electrostatic potential (MEP) analysis confirmed the bioactivity of the MMNPC molecule. The charge delocalization and stability of the title compound were studied using natural bond orbital analysis. All experimental spectral values from FT-IR, FT-Raman, UV–VIS, and 13C NMR are in good agreement with the value calculated by the DFT. Molecular docking analysis was carried out to find the MMNPC compound that can be used as a potential drug development candidate for ovarian cancer.

Chemical reactivity of 3-substituted-6,8-dimethylchromones towards 1H-benzimidazol-2-ylacetonitrile and 5-amino-2,4-dihydro-3H-pyrazol-3-one: Spectroscopic, theoretical and in silico ADME studies

The reactivity of 1H-benzimidazol-2-ylacetonitrile and 5-amino-2,4-dihydro-3H-pyrazol-3-one, as nucleophilic reagents, was examined towards some 3-substituted-6,8-dimethylchromones 2a-d. A diversity of novel pyrido[1,2-a]benzimidazoles, chromeno[2,3-b]pyridines, pyrazolo[3,4-b]pyridines and chromenopyrazolopyridines was efficiently synthesized through different chemical transformations; depending on the functional group present at C-3 position of the chromone moiety. With B3LYP/6–311 G(d,p) basis set in the ground state, density functional theory (DFT) is used to determine the molecular geometry of synthesized compounds. The reactivity of the current compounds was studied by global reactivity descriptors at the same level of theory. In order to forecast the reactive locations on the starting substrates 2a-d for nucleophilic and electrophilic attacks, Fukui functions (local reactivity descriptors) were computed at the same level of theory. On the other hand, molecular electrostatic potential (MEP) surface maps were used to identify the nucleophilic and electrophilic sites. Moreover, 1H and 13C NMR chemical shift values in the ground state was calculated using the Gauge-Including Atomic Orbital (GIAO) technique, and the predicted values were compared with the experimental results. To interpret the nonlinear optical (NLO) property of the synthesized compounds, the dipole moment, polarizability, and first hyperpolarizability values have been measured (in the range β = 0.38 × 1030 - 3.28 × 10−30 esu). First hyperpolarizabilities of the investigated compounds indicate promising candidates for nonlinear optical applications. Also, using web-based platforms, in silico ADME calculations were performed.

Bioactivity and quantum chemical calculations оf a new coumarine derivative as a strong antioxidant, antimicrobial and anti-cancer substance

4-(((4-Ethyl-5-(thiophen-2-yl)-4H-1,2,4-triazol-3-yl)thio)methyl)-7-methyl-coumarin was synthesized, and its characterization was done with quantum chemical calculations and spectral techniques. The density functional method (B3LYP) with the 6-311G(d,p) basis set was used to calculate the molecular geometry, vibrational frequencies, and gauge, including atomic orbital (GIAO) 1H and 13C-NMR chemical shift values of the title compound in the ground state. The theoretical vibrational frequencies and chemical shift values agree well with the experimental results. DFT calculations of the density of states (DOS) and frontier molecular orbitals of the title compound were carried out at the B3LYP/6-311G(d,p) level of theory. In the present study, biological activities and molecular docking studies of this triazole ring containing coumarin derivative compound were carried out. Interactions with important residues in active sites were detected in molecular docking studies. In addition, in vitro analysis has shown that anti-microorganism activity is especially effective against bacterial organisms such as E. coli, S. aureus, B. cereus, and fungal organisms such as C. albicans, C. tropicalis. Also, the antioxidant capacity of the test compound was investigated by oxidative stress index (OSI) and radical scavenging power (DPPH.), and its antioxidant potential was found. In addition, it was determined by in vitro anticancer and SDS-PAGE analysis that the test compound does not cause a detrimental cytotoxic effect on healthy cell cultures such as HUVEC and has the potential for anticarcinogenic activity on MCF-7 and MKN-45 cancerous cell cultures.

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.

Structure Revision of Balsamisides A-D and Establishment of an Empirical Rule for Distinguishing Four Classes of Biflavonoids.

Balsamisides A-D (1-4) are anti-inflammatory and neurotrophic biflavonoidal glycosides originally proposed to possess an epoxide functionality at the C-2/C-3 position. However, there are inconsistencies in their 13C NMR chemical shift values with those of previously reported analogs, indicating that reanalysis of NMR data for structures of 1-4 is necessary. Computational methods aided by the DP4+ probability technique and ECD calculations enabled structural reassignment of 1-4 to have a 2,3-dihydro-3-hydroxyfuran (3-DHF) instead of an epoxide. Additionally, two new biflavonoidal glycosides, balsamisides E and F (14 and 18), possessing a 2,3-dihydro-2-hydroxyfuran (2-DHF) and a 1,4-dioxane ring, respectively, were characterized by conventional NMR and MS data analysis as well as DP4+ and ECD methods. Systematic 13C NMR analysis was performed on the four aforementioned classes of biflavonoids with a 2- or 3-DHF, epoxide, or 1,4-dioxane. As a result, diagnostic 13C NMR chemical shift values of C-2/C-3 for rapid determination of these four biflavonoid classes were formulated, and based on this first empirical rule for (bi)flavonoids eight previously reported ones were structurally revised.

Theoretical Investigation of 1H and 13C NMR Spectra of Diethanol Amine Dithiocarbamate RAFT Agent

In this study, quantum chemical studies of diethanolamine dithiocarbamate (DADC) RAFT compound were carried out. For this purpose, the composite was optimized by using the DFT / B3LYP method 6-311G and the B3PW91 method SDD basis set. By using the optimized structure obtained according to the GIAO method, 1H and 13C NMR chemical shift values in the gas phase were calculated. According to the results obtained, it was seen that the theoretical data were coherent with the experimental data. In addition, in the theoretical part of the study, the FT-IR frequency values of the compound synthesized by using the same methods and basic set were compared experimentally and theoretically. In addition, the structure details and analysis of molecules, electronic properties such as HOMO and LUMO energies, molecular electrostatic potential (MEP) and thermodynamic properties have been performed. The electric dipole moment (μ) and the initial hyperpolarizability (β) values of the studied molecule were calculated by using ab initio quantum mechanical calculations. In addition, the calculated results show that the (DADC) molecule can have nonlinear optical (NLO) behavior with nonzero values. Neutral Band Orbital (NBO) analysis has been calculated with DFT / B3PW91/SDD basis set.

Synthesis and computational studies on a coumarin derivative: 4-chloromethyl coumarin-7-yl-methacrylate

In this article, we report the synthesis, X-ray structure determination, geometric parameters, vibrational frequencies, NMR, and UV spectra of a coumarin derivative titled 4-chloromethyl coumarin-7-yl-methacrylate (CCMA). In the study, the theoretical vibrational frequencies, NMR and UV spectra, and optimized geometric parameters were computed by using density functional theory with the hybrid methods B3LYP/6-31+G(d,p) basis set. The optimized geometric parameters, vibrational frequencies, and 1H and 13C NMR chemical shifts values were contrasted with experimental values of the title molecule. The theoretical vibrational frequencies were found in concordance with the matching experimental data. The electronic properties of the molecule were studied using the molecular frontier orbital energies, ESP surfaces, the natural bond orbital (NBO), and nonlinear optical (NLO) properties. The study findings show that the molecule has nucleophilic regions around O atoms and the transition from the ground state to the first excited state with the electronic absorption peaks at 318.19 nm in gas. In this study, the remarkable electron delocalization occurred between the donor (C4-C5) anti bond and acceptor (C6-C9) anti bond with 249.60 kcal/mol stabilization energy in the title molecule. Calculated NLO parameters show that CCMA can be used as the NLO material.

Spectroscopic analysis, DFT studies and molecular docking of 2,3‐dichloro‐benzylidine‐(2‐trifluoromethyl‐phenol)‐amine

Abstract2,3‐dichloro‐benzylidine‐(2‐trifluoromethyl‐phenol)‐amine (2DBTP) has been synthesized and characterized by various spectroscopic techniques including FT‐IR, FT‐Raman, UV‐Vis and 1H, 13C NMR spectroscopy. The equilibrium geometry and harmonic vibrational frequencies were investigated by density functional theory (DFT) at B3LYP/6‐311++G(d,p) basis set. The vibrational wavenumber assignments were made on the basis of total energy distribution (TED) calculations using Veda 4 program. The harmonic wavenumbers calculated at DFT were in line with the experimental values. The non‐linear optical properties (NLO) were calculated. Stability of the molecule arises from hyperconjugative interactions and charge delocalization was analyzed by natural bond orbital (NBO) analysis. Molecular electrostatic potential (MEP), mulliken atomic charges were also calculated. The energy gap of the molecule was found by HOMO and LUMO calculation. TD‐DFT calculations have been carried out on the optimized geometry to further understand the electronic transitions in the UV‐Vis spectrum of the compound. In addition, the 1H and 13C NMR chemical shift values of 2DBTP in the ground state were also calculated using Gauge invariant atomic orbital (GIAO) method. The molecular docking solved the binding mode of 2XCT complex with the ligand. The investigated molecule revealed the inhibition activity of the ligand against anti‐bacterial protein topoisomerase DNA gyrase enzyme (PDB ID: 2XCT).

DFT-GIAO 1H and 13C-NMR Chemical Shifts Calculation of Uncaria longiflora Alkaloids

Recently, the structure elucidation of three new chiral alkaloids, namely isoformosaninol (1), formosaninol (2), and longiflorine (3), isolated from the leaves of U. longiflora var. pteropoda (Miq.) Ridsdale has been reported. Their molecular structures were initially determined by using experimental NMR data, following a systematic method for establishing the absolute configuration of pentacyclic oxindole alkaloids (POAs), and the chemical correlation method based on the known chirality of their precursor, secologanin. Indeed, the integration of the information from experimental and theoretical data can be of fundamental importance for the successful elucidation of the configurational and stereostructural assignments of organic compounds, including natural products. Thus, the present work was conducted to further support the success of this integration by focusing on the NMR data, which is the most critical spectroscopic analysis in the structural elucidation of natural products. The 1H and 13C-NMR chemical shift values for the three alkaloids were calculated using density functional theory-gauge including atomic orbitals (DFT-GIAO) approximation at the B3LYP/6-311+G(d,p) level of theory in integral equation formalism polarizable continuum model (IEF-PCM) concerning to tetramethylsilane (TMS). Statistical error analysis between the experimental and calculated supported an excellent correlation with linearity of higher than 93% and 99% for 1H and 13C-NMR chemical shifts, respectively, for the three alkaloids. The correct correspondences between experimental and calculated data sets were further supported by the mean absolute error (MAE) parameter. The present findings provide insights on the usefulness of integrating experimental and calculated NMR data to ascertain structural elucidation in easing ambiguity. 

Spectroscopic characterization, DFT calculations, and microbiological activity of 5-iodoindole

The structural, vibrational, thermodynamic, electronic, and nonlinear optical properties of 5-iodoindole were obtained using spectral methods and density functional theory calculations. Theoretical calculations were performed by the Becke-3-Lee-Yang-Parr (B3LYP) functional using DGDZVP, LANL2DZ, and 6–311++G(d,p) with DGDZVP (mixed type) basis sets. The FT-IR and FT-Raman spectra were recorded in the regions of 4000– 400 cm−1 and 4000–100 cm−1, respectively. The scaled theoretical frequency values are compared with experimental values. 1H NMR and 13C NMR chemical shift values were calculated theoretically and also measured experimentally. The antimicrobial activity of 5-iodoindole was investigated in this study. While the title molecule shows antimicrobial activity against S. aureus ATCC 29213, S. epidermidis ATCC 35984, C. violeceum ATCC 12472, and B. cereus 709 Roma, it doesn't inhibit the growth of other bacteria and yeasts.

A Comparative Study of DFT/B3LYP/6-31 G(d,p), RM062X/6-31G8d,p), B3LYP/6-311++ G(d,p) and HSEH1PBE/6-31G(d,p) Methods Applied to Molecular Geometry and Electronic properties of Cs-C60 Cl6 Molecule

In this study, four different levels, B3LYP/6-31G(d,p), RM062X/6-31G(d,p), B3LYP/6-311++G(d,p) and HSEH1PBE/6-31G(d,p) of the DFT quantum chemical calculation method have been applied to the molecular structure of the Cs-C60Cl6 molecule as a halogenated fullerene. Additionally, the molecular structure of pure C60 fullerene was presented as complementary and supportive work. Furthermore, the simulated FT-IR, Raman and UV-Vis (in cyclohexane solvent) spectra, HOMO-LUMO analysis, the molecular electrostatic potential (MEP) map, the 13C NMR chemical shift values in both gas phase and tetrachloromethane with deuterated chloroform solvent and the thermodynamics properties at the mentioned levels of the Cs-C60Cl6 molecule were reported. Fullerene has many physical and electrochemical properties, which can be utilized in several medical fields. Especially, it can fit inside the hydrophobic cavity of HIV proteases, restricting the get into substrates to the catalytic site of the enzyme. Hence, it is utilizable as an antioxidant and radical scavenger.

Effect of donor and acceptor on optoelectronic properties of benzo[1,2-b:4,5-b′]dithiophene

A series of acceptor and donor groups anchored to benzo[1,2-b:4,5-b′]dithiophene (BDT) molecule have been systematically investigated at the density functional theory (DFT) and time-dependent density functional theory (TDDFT) level to reveal structure–property relationships, charge transfer, and fluorescence lifetimes. The DFT optimization shows that the hetero atom in the ring induces the polarity from central ring to both ends of the thiophene ring, participating in the conjugation. The donor and acceptor groups were anchored at the terminals of the BDT at two different positions to fine-tune the properties according to the requirement and study the push–pull effect. All the models studied in this work retain their aromaticity as estimated from NICS(0) and NICS(1) aromaticity index in ground and excited states. The results show that the hardness, softness, HOMO–LUMO gaps, ionization potentials (IP), and electron affinities (EA) of the BDTs are significantly affected by the electron-withdrawing and electron-donating groups. The 1H and 13C NMR chemical shift values have been computed to quantify the push–pull effect. Further, the charge transfer properties in these BDTs were explored based on reorganization energies and diagnostic descriptors derived from hole–electron theory that present different electron excitation behavior. The relationship between the computed variables such as highest occupied molecular orbital, lowest unoccupied molecular orbital, oscillator strength, dipole moment, absorption, and fluorescence energy correlates the system with one another and also to extend the possible applications of the system in optical devices. Structure–property relationship of various BDTs reveal that, upon optical excitation, the resonance effect plays an important role changing the bonding character between the substituent and BDT unit, enabling efficient electron delocalization. The examination of TDDFT results indicates that among the various models studied in this work, nitro-substituted model is better candidate for optoelectronic properties with relatively large absorption wavelength and long fluorescence lifetime.

Synthesis and substituent effect study on 13C NMR chemical shifts of 4-(substitue-phenyl)-6-methyl-3-phenyl-4H-1,2,4-oxadiazin-5(6H)-one

The twelve novel 4-(substituted-phenyl)-6-methyl-3-phenyl-4H-1,2,4-oxadiazin-5(6H)-one derivatives were synthesized by the reactions of N-Substituted-phenyl-benzamide oximes with 2-bromopropionyl chloride. The synthesized 1,2,4-oxadiazin-5-one derivatives were characterized by their physical constants and IR, 1H NMR, 13C NMR and LC/TOF-MS analyses data. The experimental 13C NMR chemical shifts (ppm) (SSC) of the C=O, C=N, CH and CH3 carbons of these 1,2,4-oxadiazin-5-one derivatives were correlated with the various Hammett substitution constants and Swain-Lupton parameters, using single (SSP) and multi-linear (DSP) regression analysis. Negative ρI and ρR values were found for correlations of C=O, C=N and CH3 carbons (reverse substituent effect). For the other carbon (CH), positive ρI (normal substitution effect) and negative ρR (reverse substitution effect) values were calculated by DSP regression analysis. As a result of DSP regression analysis, the 13C NMR chemical shift of the C=O, C=N and CH carbons of the oxadiazine ring showed a satisfactory correlation (r > 0.90), while excellent correlation was observed at the CH3 carbon (r = 0.99). The 13C NMR chemical shift values of the C=O, C=N, CH and CH3 carbons of the p-Br-substituted 1,2,4-oxadiazin-5-one derivative were estimated using the equations obtained by the DSP regression analysis. These predicted 13C NMR chemical shifts were compared with experimental 13C NMR chemical shifts for 4-(4-bromophenyl)-6-methyl-3-phenyl-4H-1,2,4-oxadiazine-5(6H)-one derivatives.

Spectroscopic Studies (FT-IR, FT-Raman and UV-Vis), NBO Analysis, HOMO-LUMO, First Order Hyperpolarizability and Docking Studies of 4-[4-(Bromo-Phenylimino)-Methyl]-2-Ethoxy Phenol

The FT-IR, FT-Raman and UV-Vis spectra of 4-[4-(bromo-phenylimino)-methyl]-2-ethoxy phenol (4BPMEP) were recorded and analyzed. The optimized geometrical parameters were calculated. The total energy distribution (TED) analysis was used to find the complete vibrational assignments. The UV-Vis spectra were recorded and analyzed. The hyper conjugative interaction energy E(2) and donor (i), acceptor (j) electron densities (EDs) were calculated by natural bond orbital (NBO) analysis. The band gap energy of 4BPMEP was calculated by highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) analysis. The electronic transition was studied by UV-Vis analysis of 4BPMEP with B3LYP/6-311++G(d,p) level of basis set. The non - linear optical (NLO) behavior, molecular electrostatic potential (MEP) and thermodynamic properties were also calculated. In addition, Gauge invariant atomic orbital (GIAO) method was used to calculate 1H and 13C NMR chemical shift values of 4BPMEP in the ground state at B3LYP/6-311++G(d,p) basis set. To establish the information about interactions between topoisomerase DNA gyrase enzymes and the novel compound, docking studies were carried out by Schrödinger software.

Molecular, Electronic, Nonlinear Optical and Spectroscopic Analysis of Heterocyclic 3-Substituted-4-(3-methyl-2-thienylmethyleneamino)-4,5-dihydro-1H-1,2,4-triazol-5-ones: Experiment and DFT Calculations

Abstract In the present study, 3-p-methoxybenzyl/m-chlorobenzyl/phenyl-4-(3-methyl-2-thienylmethyleneamino)-4,5-dihydro-1H-1,2,4-triazol-5-ones were obtained from the reaction between 3-methylthiophene-2-carbaldehyde and three different 4-amino-(3-p-methoxybenzyl/m-chlorobenzyl/phenyl)-4,5-dihydro-1H-1,2,4-triazole-5-ones. In order to compare experimental and theoretical values, the geometric parameter, electronic, nonlinear optical properties, molecular electrostatic potentials and spectroscopic properties of 3-substituted-4-(3-methyl-2-thienylmethyleneamino)-4,5-dihydro-1H-1,2,4-triazol-5-ones have been simulated. The electronic properties of the newly synthesized compounds were calculated using DFT/B3LYP and DFT/B3PW91 methods revealing parameters such as ionization potential, electron affinity, energy gap, electronegativity, molecular hardness, molecular softness, electrophilic index, nucleophilic index and chemical potential, all obtained from HOMO and LUMO energies, dipole moments and total energies. UV-visible absorption spectra and the stimulation contributions in UV-visible transitions were obtained by using TD-DFT/B3LYP/6-311G(d,p) and TD-DFT/B3PW91/6-311G(d,p) methods in ethanol. The calculated absorption wavelengths, oscillator power and excitation energies were compared with experimental values. In line with DFT, the numbers of molecular vibration were analyzed through the basis set of 6-311G(d,p). The recording of FT-IR frequencies was done for the pertinent compound. The recorded frequencies through DFT/B3LYP and DFT/B3PW91 methods were compared to experimental values, with a result gained closest to the values of B3LYP. Finally, the Gaussian09W program package in DMSO phase, starting from the optimized structure, has been instrumental in calculating the 13C-NMR and 1H-NMR chemical shift values of the GIAO method.