FT-Raman and FT-IR spectra, vibrational assignments and density functional studies of 5-bromo-2-nitropyridine

Thermal Decomposition of 2-Cyclopentenone

The thermal decomposition of 2-cyclopentenone, a cyclic oxygenated hydrocarbon that occurs in the pyrolysis of biomass, has been studied in a combined experimental and theoretical approach. Gas-phase pyrolysis was performed at temperatures ranging from 1000 to 1400 K in a pulsed, microtubular reactor. Products were identified by FTIR spectroscopy following their isolation in a low-temperature argon matrix. The following products were identified: carbon monoxide, ketene, propenylketene, vinylacetylene, ethylene, propene, acrolein, acetylene, propyne, and propargyl radical. Computational results identify three different decomposition channels involving a H atom migration, and producing prop-2-enylketene (Pathway 1), prop-1-enylketene (Pathway 2), and a second conformation of prop-2-enylketene (Pathway 3). A fourth decomposition pathway involves simultaneous rupture of two C-C bonds forming a high energy cyclopropenone intermediate that further reacts to form ethylene, acetylene, and carbon monoxide. Finally, a fifth pathway to the formation of acrolein and acetylene was identified that proceeds via a multistep mechanism, and an interconversion from 2-cyclopentenone to 3-cyclopentenone was identified computationally, but not observed experimentally.

Structural characterization and keto-enol tautomerization of 4-substituted pyrazolone derivatives with DFT approach

The synthesis of two pyrazolone derivative compounds, PYR-I(4-Acetyl-1-(4-chlorophenyl)-3-isopropyl-1H-pyrazol-5(4H)-one) and PYR-II1-(4-Chlorophenyl))-3-isopropyl-5-oxo-4,5-5-dihydro-1H-pyrazole-4-carbaldehyde, their characterization by FT-IR, NMR, UV-Vis and GC-MS techniques, and the evaluation of the keto-enol tautomerization process of the structures along with the DFT approach and spectral data were reported in this paper. Spectral findings indicated that PYR-I was stable at the keto state. The IR spectrum recorded in solid form showed that the PYR-II structure was stable in the enol state, while the NMR spectrum in the solution medium showed that it was stable in the keto state. DFT-based analyses were realized with the B3LYP hybrid functional and the 6-311++G(d,p) basis set. The modelled keto, transition and enol state molecular geometries of structures were optimized in the gas phase and different solvent media and the total energy and dipole moment values were investigated at the specified theoretical level. The possible keto-enol tautomerism mechanism of the structures was evaluated through some thermodynamic parameters such as the difference in free Gibbs energy (ΔG), enthalpy (ΔH), entropy (ΔS), and predictive tautomeric equilibrium constants (Keq), acidity constants (pKa) and percentages of tautomers at 298.15 K and 1 atm pressure. The results of these analyses based on the DFT approach indicated that the keto-enol tautomer equilibrium heavily favours the keto form for PYR-I and the enol form for PYR-II in all cases. Moreover, natural bond orbital (NBO) analysis was performed for the tautomers, and the chemical reactivity profiles of the most stable tautomers were examined with the values of frontier molecular orbital energy and some reactivity descriptors.

FT-IR, FT-raman and UV spectra and ab initio HF and DFT study of conformational analysis, molecular structure and properties of ortho- meta- and para-chlorophenylboronic acid isomers

In this study, the FT-IR, FT-Raman, and UV-Vis spectroscopic properties of three monosubstituted phenylboronic acid derivatives: ortho-chlorophenylboronic acid (o-ClPhBA), meta-chlorophenylboronic acid (m-ClPhBA) and para-chlorophenylboronic acid (p-ClPhBA) molecules are investigated both experimentally and theoretically using Density Functional Theory (B3LYP) and Hartree Fock (HF). In order to find the stable possible conformations of the compounds, the conformational analysis was carried out by running potential energy surface (PES) scan by means of rotation of two structural parameters, the dihedral angles indicated as φ2 (C6-B-O1-H1A) and φ3 (C6-B-O2-H2A), varying from -180° to 180° with an increment of 10° using B3LYP/6-31G level of theory. Also, to determinate the most stable conformer for all the molecules, potential energy curve (PEC) the stable possible conformations on PES scan were investigated as a function of φ1 (C1-C6-B-O1) dihedral angle from 0° up to 180° with an increment of 10° using B3LYP/6-311++G(d,p) and HF/6-311++G(d,p) level of theory. For all the studied compounds, two conformational structures (conformer anti-anti, syn-syn) that did not have imaginary frequency values outside the equilibrium state (conformer anti-syn) were detected theoretically at the both methods. Due to their conformational flexibility, the relative stabilities of the anti-syn, anti-anti, and syn-syn conformers of o-ClPhBA, m-ClPhBA, and p-ClPhBA are 0.0, 4.66, and 6.76 kcal/mol, respectively, at the B3LYP/6-311++G(d,p) level of theory. For the HF/6-311++G(d,p) level of theory, the relative stabilities are 0.00, 4.54, and 6.11 kcal/mol for o-ClPhBA; 0.00, 3.98, and 1.51 kcal/mol for m-ClPhBA; and 0.00, 4.10, and 1.44 kcal/mol for p-ClPhBA, respectively. Some of the determined stable conformations of these molecules are different in symmetry groups. It was observed that the increase in the symmetry was effective in the of molecular properties, especially for vibrational frequencies. The structural parameter, dipole moments (μ), vibrational frequencies, polarizability (α), hyperpolarizability (β), the highest occupied molecular orbital (HOMO), and the lowest unoccupied molecular orbital (LUMO) of the stable conformers were calculated by using Ab initio HF/6-311++G(d,p) and DFT/B3LYP/6-311++G(d,p) level of theory. The assignments of fundamental vibrational modes of the studied molecule were performed based on total energy distribution (TED) analysis.

Spectroscopic, computational, cytotoxicity, and docking studies of 6-bromobenzimidazole as anti-breast cancer agent

6-Bromobenzimidazole (6BBZ) has been calculated in this study utilizing the 6-311++G(d,p) basis set and the Becke-3-Lee-Yang-Parr density functional approaches. The basic frequencies and geometric optimization are known. FTIR, FT-Raman, and UV-Vis spectra of the substance are compared between its computed and observed values. The energy gap between highest occupied molecular orbital-lowest unoccupied molecular orbital and molecule electrostatic potentials has been represented by charge density distributions that may be associated with the biological response. Time-dependent density functional theory calculations in the gas phase and dimethyl sulfoxide were carried out to ascertain the electronic properties and energy gap values using the same basis set. Molecular orbital contributions are investigated using the overlap population, partial, and total densities of states. Natural bond analysis was found to have strong electron delocalization by means of π(C4-C9) → π*(C5-C6), LP (N1) → π*(C7-C8), and LP(Br12) → π*(C5-C6) interactions. The Fukui function and Mulliken analysis have been explored on the atomic charges of the molecule. The nuclear magnetic resonance chemical shifts for 1 H and 13 C have been computed using the gauge-independent atomic orbital technique. With the highest binding affinity (-6.2 kcal mol-1 ) against estrogen sulfotransferase receptor (PDB ID: 1AQU) and low IC50 value of 17.23 μg/mL, 6BBZ demonstrated potent action against the MCF-7 breast cancer cell line. Studies on the antibacterial activity and ADMET prediction of the molecule have also been carried out.

Structural, optimization of and mechanistic insights into a new thiosemicarbazone derivative as a highly sensitive and selective chemosensor for Hg2+ recognition using DFT, COSMO-RS, RSM, and molecular dynamics simulation approaches

A new thiosemicarbazone derivative, N-(2-hydroxyphenyl)-2-[1-(pyridin-4-yl)ethylidene]hydrazinecarbothioamide (HPEH), has been synthesized, characterized, and further developed as a highly selective and sensitive colorimetric chemosensor for Hg2+ recognition in environmental water samples. Structural conformers of HPEH were successfully identified using a combination of the potential energy surface (PES) and time-dependent density functional theory (TD-DFT) methods. The synthesized HPEH was successfully characterized further and analyzed based on its harmonic vibrational frequencies, NMR spectra, and electronic transitions using the DFT approach. Sigma profiles were generated using the COSMO-RS approach to identify a compatible medium for HPEH to act as a chemosensor. The conditions for the highly sensitive and selective detection of Hg2+ by HPEH were successfully optimized using the statistical response surface methodology approach. The optimum sensing of HPEH occurred in an 8:2 v/v DMSO/pH 7.8 solution at a 20:60 μM HPEH/Hg2+ concentration and after a reaction time of 18 min, with statistically significant independent variables (p < 0.05) for all parameters. Under optimal conditions, the lowest Hg2+ concentration detected by HPEH was 3.56 µM, indicating that HPEH can serve as an alternative and comparable probe for the detection of Hg2+ in aqueous systems. Using the optimized results, the interaction between HPEH and Hg2+ in the chemosensor system was successfully modeled, and the model was subsequently used with the TD-DFT, non-covalent interaction-reduced density gradient (NCI-RDG), and molecular dynamics approaches to gain mechanistic insights into the interaction. The results showed that the newly synthesized HPEH, in addition to being cost-effective, could serve as a suitable alternative and comparable chemosensor for Hg2+ recognition in water samples, with the advantages of being efficient, portable, and eco-friendly, and offering rapid analysis without the need of specialized training.

Studies of temperature dependent Raman spectroscopy of two nematic liquid crystalline compounds of homologous series

Raman spectroscopy is an important tool to understand the structural and molecular behaviour of the liquid crystals when they undergo through different temperatures. It also helps to understand the different phase changes of the liquid crystal material as temperature changes. In this work, the structural properties of two nematic liquid crystals having relatively high clearing temperature namely 4 butylcyclohexyl-3, 5-difluoro-4- isothiocyanato biphenyl and 4-pentylcyclohexyl-3, 5-difluoro-4-isothiocyanato biphenyl are studied. The study is done using temperature dependent Raman spectroscopy. From the studies of the two compounds it has been found that the experimental values are agree well with the various functional groups and different bond assignments recorded in literature. This agreement validates the presence of different functional groups and different stretching bonds in the two studied liquid crystal compounds. Deformations of some of the peak positions of the two liquid crystal compounds have been observed with the change in phase at different temperature. Also to understand the behaviour of the Raman peak near the clearing temperatures of the liquid crystal compounds the linewidth of the different peak values at different temperature have also been studied. From the line width study, the various phase transition temperatures of the two liquid crystalline compounds can be confirmed.

Experimental and theoretical study on the regioselective bis- or polyalkylation of 6-amino-2-mercapto-3H-pyrimidin-4-one using zeolite nano-gold catalyst and a quantum hybrid computational method

The synthetic utility of 6-amino-2-mercapto-3H-pyrimidin-4-one 3 as building blocks for new poly (pyrimidine) by alkylation using the bis(halo) compounds and zeolite nano-gold as a catalyst was investigated. Furthermore, the experimental findings by the theoretical Density functional theory (DFT) computations at the DFT/B3LYP level of theory, utilizing the 6-311++G (d,p) basis set in the gas phase, were used to investigate the distinct phases for Regio isomer 11a & 12a and 11b & 12b compounds was fair and of good quality. The stability of the 12a and 12b phases is higher than the other Regio isomer 11a and 11b phases, according to DFT modelling. By computing HOMO and LUMO pictures, the electronic parameters: dipole moment of these compounds in the ground state were theoretically investigated. Non-linear optical (NLO) characteristics and quantum chemical parameters were examined using frontier molecular orbital (FMO) analysis. Natural bond orbital analysis was used to characterize the charge transfer of the electron density in the investigated compounds (NBO). The molecular electrostatic potential surfaces (MEPS) plots have been generated, and absorption spectral analysis in different solvents has been theoretically and experimentally examined to better understand the reactivity spots. At the B3LYP/6-311G (d,p) level of theory, thermodynamic properties were also calculated. Finally, DFT calculations were used to connect the structure-activity relationship (SAR) with real antibacterial results for compounds 12a and 12b.

Methemoglobinemia and Delayed Encephalopathy After 5-Bromo-2-Nitropyridine Poisoning: A Rare Case Report

5-bromo-2-nitropyridine, an intermediate in the synthesis of pharmaceutical and pesticide products, is toxic to the human body. However, 5-bromo-2-nitropyridine poisoning has not been previously reported. Here, we report the case of a 40-year-old man who suffered skin and respiratory tract exposure to leaked 5-Bromo-2-nitropyridine at work. After exposure, the patient rapidly developed dizziness, fatigue, nausea, vomiting, chest distress, diffuse cyanosis, and coma. Methemoglobinemia, hemolytic anemia, rhabdomyolysis, and acute renal failure were observed after admission. He improved markedly after treatment, but delayed encephalopathy was confirmed 82 days after the exposure. This case highlights that 5-bromo-2-nitropyridine can be absorbed through the skin and respiratory tract, resulting in methemoglobinemia and delayed encephalopathy.

Synthesis, Structure, and Antiproliferative Action of 2-Pyridyl Urea-Based Cu(II) Complexes

Relying on a recently suggested protocol that furnishes convenient access to variously substituted 2-pyridyl ureas, twelve hitherto unknown Cu(II) complexes have been synthesized in the present work and their structures were evaluated by elemental analysis, HRMS, IR spectroscopy, and X-ray diffraction study. Two structural motifs ([Cu(L)2Cl]+[Cl]− or (Cu(L)2Cl2) depending on the substitution pattern on the 2-pyridine fragment were revealed. In addition, antiproliferative action of the obtained compounds have been investigated against lung cancer cell lines (A549, NCI-H460, NCI-H1975), and healthy WI-26 VA4 cells were used to monitor non-specific cytotoxicity. Two nitro-group substituted complexes Cu(U3)2Cl2 (IC50 = 39.6 ± 4.5 μM) and Cu(U11)2Cl2 (IC50 = 33.4 ± 3.8 μM) demonstrate enhanced activity against the drug resistant NCI-H1975 cells with moderate selectivity toward normal WI-26 VA4 cells. The antiproliferative mechanism of cell death underlying the growth inhibitory effect of the synthesized complexes was studied via additional experiments, including the cell cycle analysis and the apoptosis induction test. Reassuringly, certain 2-pyridyl urea-based Cu(II) complexes exerted cell line-specific antiproliferative effect which renders them valuable starting points for further unveiling the anticancer potential of this class of coordination compounds.

Synthesis, FT-IR, structural, thermochemical, electronic absorption spectral, and NLO analysis of the novel 10-methoxy-10H-furo[3,2-g]chromeno[2,3-b][1,3]thiazolo[5,4-e]pyridine-2,10(3H)-dione (MFCTP): a DFT/TD-DFT study

Chemical transformation of 4-methoxy-5-oxo-5H-furo[3,2-g]chromene-6-carbonitrile (1) with 1,3-thiazolidine-2,4-dione (2) in boiling ethanol containing piperidine afforded the novel 10-methoxy-10H-furo[3,2-g]chromeno[2,3-b][1,3]thiazole[5,4-e]pyridine-2,10(3H)-dione (3, MFCTP). The chemical structure of the synthesized compound was established via elemental analysis and spectral data. FT-IR spectroscopy was performed in the range of 400-4000 cm-1 for the vibrational spectral analysis of MFCTP. The GIAO method was employed to calculate the values of 1H and 13C NMR chemical shifts theoretically, which were consistent with the experimental chemical shifts. The molecule (3, MFCTP) has two stable structures, as determined from the potential energy curve. The S1 structure is the most stable conformer of (3, MFCTP) according to the computational results. The density functional theory (DFT) and ab initio HF calculations and different basis set combinations based on the structure optimizations and normal coordinate force field were interpreted with the aid of the molecular structure, fundamental vibrational frequencies, and intensities of the vibrational bands. The potential energy distribution (PED) was determined based on the complete vibrational wavenumber assignments. The calculated spectra of the title compound were in agreement with the observed spectra. The scaled B3LYP/6-311++G(d,p) results exhibited better agreement with the experimental values compared to the other method used. The time-dependent density functional theory (TD-DFT) was employed to calculate the energy and oscillator strength and supplement the experimental findings. Also, it was performed and the results interpreted the molecular electrostatic potential, nonlinear optical and thermodynamic properties, and Mulliken and natural charges of the title compound. DFT calculations were performed to study the structure-activity relationship (SAR) and compared with the experimental antimicrobial results for compound (3, MFCTP).

DFT Study on the Electronic Properties, Spectroscopic Profile, and Biological Activity of 2-Amino-5-trifluoromethyl-1,3,4-thiadiazole with Anticancer Properties

Extensive investigation on the molecular and electronic structure of 2-amino-5-trifluoromethyl-1,3,4-thiadiazole in the ground state and in the first excited state has been performed. The energy barrier corresponding to the conversion between imino and amino tautomers has been calculated, which indicates the existence of amino tautomer in solid state for the title compound. The FT-Raman and FT-IR spectra were recorded and compared with theoretical vibrational wavenumbers, and a good coherence has been observed. The MESP map, dipole moment, polarizability, and hyperpolarizability have been calculated to comprehend the properties of the title molecule. High polarizability value estimation of the title compound may enhance its bioactivity. Natural bonding orbital analysis has been done on monomer and dimer to investigate the charge delocalization and strength of hydrogen bonding, respectively. Strong hydrogen bonding interaction energies of 17.09/17.49 kcal mol-1 have been calculated at the B3LYP/M06-2X functional. The UV-vis spectrum was recorded and related to the theoretical spectrum. The title compound was biologically examined for anticancer activity by studying the cytotoxic performance against two human cancer cell lines (A549 and HeLa) along with the molecular docking simulation. Both molecular docking and cytotoxic performance against cancer cell lines show positive outcomes, and the title compound appears to be a promising anticancer agent.

Design, molecular docking analysis of an anti-inflammatory drug, computational analysis and intermolecular interactions energy studies of 1-benzothiophene-2-carboxylic acid

In this paper, theoretical study on molecular geometry, vibrational, pharmaceutical and electronic properties of the monomeric and dimeric structures of 1-benzothiophene-2-carboxylic acid (2BT) were carried out using B3LYP hybrid functional with 6-311++G(d,p) as basis set. The structural study show that the stability of 2BT crystalline structure arising from O-H…O, C-H…O as well as S-H…O hydrogen bonding interactions. Vibrational analysis, for monomer and dimer species, show a good compatibility between experimental and theoretical frequencies. Then, the 1H and 13C NMR chemical shifts were calculated using Gauge Independent Atomic Orbital (GIAO) technical. In addition, the UV-Vis spectrum was simulated in gas phase and in water throughout TD-DFT calculation. The electronic transitions were identified based on HOM-LUMO energies. However, donor-acceptor interactions and charge delocalization has been studied via natural bond orbital (NBO). The nucleophilic and electrophilic site localization is identified by molecular electrostatic potential. Hirshfeld surface analysis has been discussed based on color code demonstrating the various non covalent interactions. Besides, molecular docking analysis was reported to evince the pharmaceutical properties of the studied molecule.

Spectroscopic and quantum computational study on naproxen sodium

The spectroscopic (FT-IR, FT-Raman, NMR), electronic (UV--Vis.), structural and thermodynamical properties of an anti-inflammatory analgesic called Naproxen Sodium, (s)-6-methoxy-α-methyl-2-naphthaleneacetic acid sodium salt are submitted by using both experimental techniques and theoretical methods as quantum chemical calculations in this work. The equilibrium geometry and vibrational spectra are calculated by using DFT (B3LYP) with 6-311++G (d,p) basis set using GAUSSIAN 09. The vibrational wavenumbers are also corrected with scale factor to take better results for the calculated data. The HOMO-LUMO calculations are carried out on the title compound. The theoretical and experimental NMR peaks were found to be in good agreement. In addition, the detailed study on the Non-Bonding Orbitals, the excitation energies, AIM charges, condensed fukui calculations, thermodynamical properties, Localized Orbital Locator (LOL) and Electron Localization Function (ELF) are also performed. Furthermore, the study is extended to calculate the first order hyperpolarizability and to predict its NLO properties. The docking studies details helped on predicting the binding with different proteins.

Hydrogen bonding interactions in fluorinated 1,2,3-triazole derivatives

Comprehensive theoretical, structural and spectroscopic investigations on new substituted 1,2,3-triazoles in the solid state.

Molecular docking, spectroscopic studies on 4-[2-(Dipropylamino) ethyl]-1,3-dihydro-2H-indol-2-one and QSAR study of a group of dopamine agonists by density functional method

Density functional theory is one of the most popular accepted computational quantum mechanical techniques used in the analysis of molecular structure and vibrational spectra. Experimental and theoretical investigations of the molecular structure, electronic and vibrational characteristics of 4-[2-(Dipropylamino) ethyl]-1,3-dihydro-2H-indol-2-one are presented in this work. The title compound was characterized using FT-IR, FT-Raman and UV-Vis spectroscopic techniques. The results were compared with the theoretical calculations obtained using DFT/B3LYP with 6-311++G(d,p) as basis sets and was found to be in good agreement. The complete optimization of the molecular geometry of the title compound was carried out. Further, the vibrational assignments and calculation of potential energy distribution (PED) were reported. NLO has emerged as a key factor in recent researches. Materials showing nonlinear optical properties form the basis of nonlinear optics and development of such materials plays an important role in the present scenario. The current work provides sufficient justification for the title compound to be selected as a good non-linear optical (NLO) candidate. The electronic properties were reported using TD-DFT approach. The HOMO (EHOMO = -5.96 eV), LUMO (ELUMO = -0.80 eV) energies, energy gap and electrophilicity (2.22) was calculated in order to understand the stability, reactivity and bioactivity of the compound under investigation. To comprehend the bonding interactions we have performed the total (TDOS), partial (PDOS) and overlap population or COOP (Crystal Orbital Overlap Population) density of states. The drug likeness values were analyzed to evaluate the potential of the title compound to be an active pharmaceutical component. As a positive proof the paper further explains the molecular docking studies of the said compound. In addition, the stereochemistry of the protein structure was checked using Ramachandran plot. The title compound is a directly acting dopamine D2 agonist. In order to establish relationship between molecular descriptors of compound and its biological activity, QSAR studies have been done within the framework of DFT for 10 dopamine agonist including the title compound. Hence, the research exploration provides requisite information pertaining to the geometry, stability, reactivity and bioactivity of the compound through spectroscopic and quantum chemical methods.