Experimental and ab initio computational studies on 4-(1H-benzo[d]imidazol-2-yl)-N,N-dimethylaniline

Enhanced NLO response and switching self-focussing in benzodiazepine derivative with -NO2 and -Br substitution

Optoelectronic and the cubic nonlinear optical properties of 4-(4-Bromophenyl)-2-(4-nitrophenyl)-2, 3-dihydro-1H-1, 5-benzodiazepine have been studied. Z-scan technique was used for the third-order nonlinear optical measurements namely, nonlinear absorption, nonlinear refraction, and optical power limiting behaviour employing an Nd: YAG laser of 532 nm wavelength having 5 ns Gaussian pulses. B3LYP/6-311 ++ G (d, p) level of theory was employed for structural optimization, vibrational wavenumber, frontier molecular orbitals, natural bond orbital and population analysis. The MOLVIB programme was used to perform unambiguous vibrational assignments based on potential energy distribution values acquired from normal coordinate analysis. B3LYP and CAM-B3LYP hybrid functions have been employed at the DFT level to calculate the theoretical second-order hyperpolarizability. The substitution of -NO2 and -Br in this benzodiazepine compound enhances the second-order hyperpolarizability (γ) to the order of 10-34 esu and, switching of self-defocussing to self-focussing phenomenon. The HOMO-LUMO and optical band gap analysis illustrates that polarizing nature of the molecule vary with substituents. The obtained results indicate that this compound has potential applications in optoelectronics and photonics.

Dissolution mechanism of cellulose in a benzyltriethylammonium/urea deep eutectic solvent (DES): DFT-quantum modeling, molecular dynamics and experimental investigation

In this paper, a benzyltriethylammonium/urea DES was investigated as a new green and eco-friendly medium for the progress of organic chemical reactions, particularly the dissolution and the functionalization of cellulose. In this regard, the viscosity-average molecular weight of cellulose (M̄w) during the dissolution/regeneration process was investigated, showing no significant degradation of the polymer chains. Moreover, X-ray diffraction patterns indicated that the cellulose dissolution process in the BTEAB/urea DES decreased the crystallinity index from 87% to 75%, and there was no effect on type I cellulose polymorphism. However, a drastic impact of the cosolvents (water and DMSO) on the melting point of the DES was observed. Besides, to understand the evolution of cellulose-DES interactions, the formation mechanism of the system was studied in terms of H-bond density and radial distribution function (RDF) using molecular dynamics modeling. Furthermore, density functional theory (DFT) was used to evaluate the topological characteristics of the polymeric system such as potential energy density (PED), laplacian electron density (LED), energy density, and kinetic energy density (KED) at bond critical points (BCPs) between the cellulose and the DES. The quantum theory of atoms in molecules (AIM), Bader's quantum theory (BQT), and reduced density gradient (RDG) scatter plots have been exploited to estimate and locate non-covalent interactions (NCIs). The results revealed that the dissolution process is attributed to the physical interactions, mainly the strong H-bond interactions.

A DFT study of vibrational spectra of 5-chlorouracil with molecular structure, HOMO-LUMO, MEPs/ESPs and thermodynamic properties

The density functional theory calculation has been carried out for the analysis of 5-chlorouracil using DFT/Gaussian 09 with GAR2PED. Recorded experimental spectra for Raman and IR of 5-chlorouracil have been analyzed all fundamental vibrational modes using the outcome results of DFT at 6-311++G** of Gaussian 09 calculations and the GaussView 5.09. To help the analysis of vibrational modes, GAR2PED program has been used in the calculation of PEDs. The charge transfer properties of 5-chlorouracil have been analyzed using HOMO and LUMO level energy analysis. HOMO and LUMO energy gap study supports the charge transfer possibility in molecule. These have been made to study for reactivity and stability of heterocyclic molecules for the analysis of antiviral drugs against the new corona virus: COVID-19. Here, the smaller energy gap of 5-chlorouracil is more responsible for charge transfer interaction in the heterocyclic drug molecules and a reason of more bioactivity. The electron density mapping within molecular electrostatic potential plot and electrostatic potential plotting within iso-surface plot have been evaluated the charge distribution concept in the molecule as the nucleophilic reactions and electrophilic sites. These computations have been used to produce the molecular charges, structure and thermodynamic functions of biomolecule. This study has been made to all internal modes of chloro group substituent at pyrimidine ring of C₅ atom. The splitting of frequencies has arisen in the two species for the normal distribution modes.

Graphical abstract

Tumoricidal Potential of Novel Amino-1,10-phenanthroline Derived Imine Ligands: Chemical Preparation, Structure, and Biological Investigations

Herein we report the synthesis and structural elucidation of two novel imine-based ligands, 2-(1,10-phenanthrolin-5-yl)imino)methyl)-5-bromophenol (PIB) and N-(1,10-phenanthrolin-5-yl)-1-(thiophen-3-yl)methanimine (PTM) ligands. An in vitro cytotoxicity assay of the synthesized molecules was carried out against breast, cervical, colorectal, and prostate cancer cell lines as well as immortalized human keratinocytes. The observations indicated that both the molecules possesses dose-dependent selective cytotoxicity of cancer cells with no detrimental effect on the normal cell lines. Furthermore, the detailed computational analysis of newly synthetized ligands (PIB and PTM) has been conducted in order to identify their most important parts from the perspective of local reactivity. The IC₅₀ values of PIB treatment on MCF-7, HeLa, HCT-116 and PC-3 were 15.10, 16.25, 17.88, 17.55 and 23.86 micromoles, respectively. Meanwhile, the IC₅₀ values of PTM on MCF-7, HeLa, HCT-116, PC-3 and HaCat were observed to be 14.82, 15.03, 17.88, 17.28 and 21.22 micromoles, respectively. For computational analysis, we have employed the combination of Density Functional Theory (DFT) calculations and MD simulations. DFT calculations provided us with information about structure and reactivity descriptors based on the electron distribution. Surfaces of molecular electrostatic potential (MEP) and averaged local ionization energy (ALIE) indicated the sites within studied molecules that are most reactive. These results indicated the importance of nitrogen atoms and OH group. Additionally, the values of bond dissociation for hydrogen abstraction showed that both molecules, especially the PTM, are stable toward the influence of autoxidation mechanism. On the other side, MD simulations gave us an insight how ligands interact with water molecules. Namely, the radial distribution functions (RDF) indicated that the hydrogen atom of the OH group in the case of the PIB has the most pronounced interactions with water.

Synthesis, characterization, anti-diabetic potential and DFT studies of 7-hydroxy-4-methyl-2-oxo-2H-chromene-8-carbaldehyde oxime

A new compound named 7-hydroxy-4-methyl-2-oxo-2H-chromene-8-carbaldehyde oxime (7-Oxime) was synthesized and characterized by FT-IR, FT-Raman, ¹H NMR and ¹³C NMR techniques. The conformer possibilities were studied to find the most stable conformer and its molecular geometry. Then, the dimer form of the most stable monomer was built and optimized. Density functional theory (DFT) B3LYP method with 6-311++G(d,p) basis set was applied to analyze the molecular electrostatic potential (MEP), HOMO and LUMO orbitals, the vibrational wavenumbers, the infrared intensities, the Raman scattering activities and several thermodynamic properties (at different temperatures). The stability of the molecule derived from hyperconjugative interactions and charge delocalization has been analyzed by using natural bond orbital (NBO) analysis. In order to find the possible inhibitory activity of 7-Oxime, an accurate molecular blind docking simulation was performed. The results indicated that the mentioned compound has a good binding affinity to interact with the active sites of human α-glucosidase and α-amylase. For the first time, our computational finding suggests that this compound has a potential to be used as a supplementary agent in the pre-management of diabetes mellitus.

Remarkable colorimetric sensing behavior of pyrazole-based chemosensor towards Cu(ii) ion detection: synthesis, characterization and theoretical investigations

We report the synthesis of a new imine based ligand, 3-((3-methoxybenzylidene)amino)-1H-pyrazol-5-ol (HL) and its Cu(ii) complexes in 2 : 1 (HL : metal) and 1 : 1 : 1 (HL : metal : HQ) stoichiometric ratio using 8-hydroxyquinoline (HQ) as an additional bidentate ligand. The synthesized ligand (HL) and its Cu(ii) complexes (1 and 2) are structurally characterized using FT-IR, electronic absorption and emission, NMR and MS techniques. Furthermore, the complexation of Cu2+ with HL leads to the immediate formation of brown colour solution which indicates that HL can act as simple colorimetric sensor for Cu2+ ions. We further investigated that the sensor could selectively bind to the Cu2+ ions even in the presence of competitive ions such as Mn2+, Fe2+, Co2+, Ni2+, Zn2+, Ag+ and Na+ ions in aqueous solutions which was studied by electronic absorption spectroscopy. The HL ligand has been investigated for its reactive properties by density functional theory (DFT) calculations. Quantum molecular descriptors describing local reactive properties have been calculated in order to identify the most reactive molecule sites of title compounds. DFT calculations encompassed molecular electrostatic potential (MEP), local average ionization energies (ALIE), Fukui functions and bond dissociation energies for hydrogen abstraction (H-BDE).

Structural, spectroscopic (FT-IR, FT-Raman, NMR) and computational analysis (DOS, NBO, Fukui) of 3,5-dimethylisoxazole and 4-(chloromethyl)-3,5-dimethylisoxazole: A DFT study

The theoretical and computational analysis of two isoxazole derivatives 3,5-dimethylisoxazole and 4-chloromethyl-3,5-dimethylisoxazole were carried out along with some of the experimental evidences. The density functional theory calculations of these compounds were done with DFT/B3LYP/6-31+G(d,p) basis set using Gaussian 09 software. From the DFT calculations, the optimization geometry, vibrational analysis, electronic properties, local reactivity descriptors, natural bond orbitals, and other structural properties of the title compounds were elucidated. The chemical shifts of every C and H atom of the title compounds were calculated using Gauge Independent Atomic orbitals (GIAO) method for both proton and carbon NMR spectra. The molecular electrostatic potential of DMI has been found out and the difference in MEP on addition of chloromethyl group is also discussed. The hyperpolarizability calculations of the investigated molecules shows that the nonlinear optical activity of CDMI is greater when compared to DMI.

Quantum chemical calculations and interpretation of electronic transitions and spectroscopic characteristics belonging to 1-(3-Mesityl-3-methylcyclobutyl)-2-(naphthalene-1-yloxy)ethanone

This comprehensive study reports the synthesis of the title compound, 1-(3-Mesityl-3-methylcyclobutyl)-2-(naphthalene-1-yloxy)ethanone (C26H28O2), and identification of the molecule by means of the standard experimental methods such as single-crystal X-ray diffraction, ultra violet-visible (UV-vis) spectra, Fourier transform infrared (FTIR) spectra, (13)C and (1)H NMR chemical shifts and quantum chemical calculations using density functional theory (B3LYP) method for the first time. The experimental results observed display that the synthesis of the C26H28O2 compound is perfectly conducted without any impurities. Additionally, the little deviations are noticed on the bond lengths and bond angles, confirming that the strong intra-molecular charge transfers appear in the due to the presence of the electron engagements and conjugative effects (bond weakening). Besides, the intermolecular C-H⋯O distance presents the interaction between the methylcyclobutyl C-H group and oxygen atom in the ethanone group. At the same time, the absorption wavelength (λmax) appears at 292 nm and interval 297-269 nm in the solvent of chloroform and THF as a consequence of the presence of effective π-π(∗) conjugated segments in the molecule studied. Besides, optical band gap energy of 3.22/3.25 eV (chloroform/THF), verifies the existence of the strong electronic donating groups in the structure. As for the quantum chemical computations, the determination of the optimized molecular structures, vibrational frequencies including infrared intensities, vibrational wavenumbers, thermodynamic properties, atomic charges, electronic transitions, dipole moment (charge distribution), optical band gap energy, (1)H and (13)C NMR chemical shifts are conducted using density functional theory/Becke-3-Lee-Yang-Parr (DFT/B3LYP) method with the standard 6-311++G(2d,2p) level of theory. The results obtained show that the strong intra-molecular charge transfer (ICT) appears between the donor and acceptor in the title compound due to the existence of the strong electronic donating groups and effective π-π(∗) conjugated segments with high electronic donor ability for the electrophilic attack (intermolecular interactions). Additionally, the presence of the non-uniform charge distributions (polar behavior) on the various atoms makes the title compound be useful to bond metallically.

Electrochemical and spectroscopic characteristics of p-acryloyloxybenzoyl chloride and p-acryloyloxybenzoic acid and antimicrobial activity of organic compounds

The purpose of this multidisciplinary work is to characterize title compounds, p-acryloyloxybenzoyl chloride (ABC) and p-acryloyloxybenzoic acid (ABA) by means of experimental and theoretical evidences. As experimental research, Fourier transformation-infrared spectra (in the region 400-4000 cm(-1)) and nuclear magnetic resonance (NMR) chemical shifts (with a frequency of 400 MHz) are examined for spectroscopic properties belonging to the new synthesized compounds. Moreover, the compounds are investigated for antimicrobial activity against various microorganisms (Gram-positive and Gram-negative) by means of the visual inhibition zone technique on the agar media. The experimental results observed indicate that ABA exhibits more powerful inhibitors of microorganisms due to the presence of the hydroxyl group leading to higher reactive system, one of the most striking features of the paper. As for the theoretical studies, the optimized molecular structures, vibrational frequencies, corresponding vibrational spectra interpreted with the aid of normal coordinate analysis based on scaled density functional force field, atomic charges, thermodynamic properties at different temperature, 1H NMR chemical shifts by way of density functional theory (DFT) with the standard (B3LYP) methods at 6-311G++(d,p) basis set combination for the first time. According to findings, the 1H NMR chemical shifts and vibrational frequencies are obtained to be in good agreement with the suitable experimental results. Thus, it would be more precise to say that the calculation level chosen is powerful approach for understanding in the identification of the molecules investigated. At the same time, we determine the electrochemical characteristics belonging to the samples via the simulation of translation energy (HOMO-LUMO), molecular electrostatic potential (MEP) and electrostatic potential (ESP) investigations. It is observed that the strong intra-molecular charge transfer (ICT) appears between the donor and acceptor in the both compounds (especially ABA) due to the existence of the strong electronic donating groups and effective π-π* conjugated segments with high electronic donor ability for the electrophilic attack (intermolecular interactions).

Synthesis, characterization and quantum chemical investigation of molecular structure and vibrational spectra of 2,5-dichloro-3,6-bis-(methylamino)1,4-benzoquinone

2,5-Dichloro-3,6-bis-methylamino-[1,4]benzoquinone has been synthesized by condensing methyl amine hydrochloride with chloranil in presence of condensing agent sodium acetate. FT-IR (4000-400 cm(-1)) and FT-Raman (4000-400 cm(-1)) spectral measurements of dmdb have been done. Ab initio and DFT (B3LYP/6-311+G(**)) calculations have been performed giving energies, optimized structures, harmonic vibrational frequencies, infrared intensities and Raman activities. The optimized molecular structure of the compound is found to possess C2h point group symmetry. A detailed interpretation of the observed IR and Raman spectra of dmdb is reported on the basis of the calculated potential energy distribution. Stability of the molecule arising from hyper conjugative interactions, charge delocalization has been analyzed using NBO analysis. The HOMO and LUMO energy gap reveals that the energy gap reflects the chemical activity of the molecule. The thermodynamic functions of the title compound have also been computed.

The spectroscopic (FT-IR, FT-Raman and NMR), NCA, Fukui function analysis first order hyperpolarizability, TGA of 6-chloro-3,4dihydro-2H-1,2,4-benzothiazine-7-sulphonamide1,1-dioxide by ab initio HF and Density Functional method

The Fourier-Transform Infrared and Fourier-Transform Raman spectra of 6-Chloro-3,4dihydro-2H-1,2,4-benzothiazine-7sulphonamide1,1-dioxide(6CDBSD) was recorded in the region 4000-450cm(-1) and 4000-100cm(-1)respectively. Quantum chemical calculations of energies, geometrical structure and vibrational wave numbers of 6CDBSD were carried out by HF and DFT (B3LYP) method with 6-31G (d,p) basis set. The difference between the observed and scaled wavenumber value of most of the fundamentals is very small. The assignments of the vibrational spectra have been carried out with the aid of normal coordinate analysis (NCA) following the scaled quantum mechanical force field methodology (SQMFF). The linear polariazability (α) and the first order hyperpolarizability (βtot) values of the investigated molecule have been computed using HF and DFT with 6-31G (d,p) basis set. Stability of the molecule arising from hyper conjugative interaction and charge delocalization has been analyzed using natural bond orbital (NBO) analysis. The (1)H and (13)C Nuclear Magnetic Resonance (NMR) chemical shifts of the molecules were calculated using the Gauge-Invariant Atomic orbital (GIAO) method, confirms with the experimental values. The calculated HOMO and LUMO energies also confirm that charge transfer occurs within the molecule. Thermal stability of 6CDBSD was studied by thermo gravimetric analysis (TGA). Next Fukui functions was calculated to identify changes in the reactivity of molecule. Finally molecular electrostatic potential (MEP) and other molecular properties were performed.

Molecular orbital studies (hardness, chemical potential and electrophilicity), vibrational investigation and theoretical NBO analysis of 4-4'-(1H-1,2,4-triazol-1-yl methylene) dibenzonitrile based on abinitio and DFT methods

The Fourier transform infrared (FTIR) and FT Raman (FTR) of 4-4'-(1H-1, 2, 4-triazol-1-yl methylene) dibenzonitrile (4-HTMDBN) have been recorded and analyzed. The equilibrium geometry harmonic vibrational frequencies have been investigated with the help of standard HF and DFT methods with 6-31G(d,p) as basis set. The assignments of the vibrational spectra have been carried out with the help of normal co-ordinate analysis (NCA) following the scaled quantum mechanical force field methodology (SQMFF). Theoretical simulations of the FTIR and FTR spectra of the title compound have been calculated. The (1)H and (13)C Nuclear Magnetic Resonance (NMR) chemical shifts of the molecule were calculated by the Gauge including atomic orbital (GIAO) method. The stability of the molecule has been analyzed using natural bond orbital (NBO) analysis. The linear polarizability (α) and the first order hyperpolarizability (β) values of the investigated molecule have been computed using HF/DFT/6-31G(d,p) methods on the finite field approach. UV-Vis spectrum of the compound is recorded and the electronic properties such as HOMO and LUMO energies, are performed. The directly calculated ionization potential (IP), electron affinity (EA), electronegativity (χ), electrophilicity index (ω), hardness (η) and chemical potential (ρ) are all correlated with the HOMO and LUMO energies with their molecular properties. Mulliken population analysis on atomic charges, molecular electrostatic potential maps (MEP) and thermodynamical properties of title compound at different temperature have been calculated.

DFT analysis of P-nitrobenzotrifluoride--a combined study of experimental (FT-IR and FT-Raman) and theoretical calculations

In this, a combined experimental and theoretical study on molecular structure and vibrational analysis of P-nitrobenzotrifluoride (PNBTF) is reported. The Fourier transform infrared and FT-Raman was recorded in the solid phase. The molecular geometry and vibrational frequencies of PNBTF in the ground state have been calculated by using density functional method (B3LYP) with 6-311++G(d,p) as basis set. Comparison of the observed fundamental vibrational frequencies with calculated results by density functional methods indicates that B3LYP/6-311++G(d,p) is superior to other methods for molecular vibrational problems. The bioactivity of the compound is analyzed by the HOMO-LUMO analysis. The reactivity sites are identified by mapping of electron density into electrostatic potential surface (MEP). Besides, (13)C and (1)H nuclear magnetic resonance (NMR) chemical shifts are calculated by using the gauge-invariant atomic orbital (GIAO) method. Furthermore, the compound can be used as a good nonlinear optical material due to the higher value of first hyperpolarizability. Solventation effect of NMR spectra by CPCM model of P-nitrobenzotrifluoride has been analyzed.

Vibrational spectra, first order hyperpolarizability, NBO, Fukui function and HOMO-LUMO analysis of 2-[4-(1,3-benzodioxol-5-ylmethyl)-1-piperazinyl] pyrimidine

In this work, the vibrational spectral analysis was carried out by using FT-Raman and FT-IR spectroscopy in the range 4000-100cm(-1) and 4000-400cm(-1) respectively, for 2-[4-(1, 3-benzodioxol-5-ylmethyl)-1-piperazinyl] pyrimidine(BDPP) molecule. Theoretical calculations were performed density functional theory (DFT) method using 6-31G(d,p) and 6-311G(d,p) basis sets. The assignments of vibrational spectra have been carried out with the help of normal co-ordinate analysis (NCA) following the scaled quantum mechanical force field (SQMFF) methodology. The results of the calculations were applied to simulated spectra of the title compound, which show excellent agreement with observed spectra. The frontier orbital energy gap and dipole moment illustrates the high reactivity of the title molecule. The first order hyperpolarizability (β0) and related properties (μ, α and Δα) of the title molecule were also calculated. Stability of the molecule has been analyzed by natural bond orbital (NBO) analysis. Global reactivity and local reactivity descriptors of the title molecule have been calculated. Mulliken population analyses on atomic charges of the title compound have been calculated. Finally, molecular electrostatic potential (MEP) and HOMO-LUMO energy levels have been performed.

FT-IR, dispersive Raman, NMR, DFT and antimicrobial activity studies on 2-(Thiophen-2-yl)-1H-benzo[d]imidazole

2-(Thiophen-2-yl)-1H-benzo[d]imidazole (TBI) was synthesized under microwave conditions and was characterized by FT-IR, dispersive Raman, (1)H-, (13)C-, DEPT-, HETCOR-NMR spectroscopies and density functional theory (DFT) computations. The FT-IR and dispersive Raman spectra of TBI were recorded in the regions 4000-400 cm(-1) and 4000-100 cm(-1). The experimental vibrational spectra were interpreted with the help of normal coordinate analysis based on DFT/B3LYP/6-311++G(d,p) theory level for the more stable tautomeric form (Tautomer 1). The complete vibrational assignments were performed on the basis of the potential energy distribution (PED) of the vibrational modes, calculated with scaled quantum mechanical (SQM) method. A satisfactory consistency between the experimental and theoretical findings was obtained. The frontier molecular orbitals (FMOs), atomic charges and NMR shifts of the two stable tautomeric forms were also obtained at the same theory level without any symmetry restrictions. In addition, the title compound was screened for its antimicrobial activity and was found to be exhibit antifungal and antibacterial effects.

Density functional theory study, FT-IR and FT-Raman spectra and SQM force field calculation for vibrational analysis of 1, 3-Bis (hydroxymethyl) benzimidazolin-2-one

FT-IR and FT-Raman spectra of 1, 3-Bis (hydroxymethyl) benzimidazolin-2-one were recorded and analyzed in the solid phase. The optimized molecular geometry and vibrational wavenumbers have also been calculated in optimized structure by using DFT method. Scaled quantum mechanical force fields have also been used to calculate potential energy distributions in order to make conspicuous vibrational assignments. The red shifting of the O-H stretching wavenumber is due to the formation of O-H···O intermolecular hydrogen bonding. The lowering and splitting of the carbonyl stretching vibrational modes is assigned to the intermolecular association based on C=O···H type hydrogen bonding in the molecule. Chemical interpretation of hyperconjugative interactions was done by natural bond orbital analysis.

Experimental and theoretical approaches for identification of p-benzophenoneoxycarbonylphenyl acrylate

The aim of this multidisciplinary study is to characterize a title compound, p-benzophenoneoxycarbonylphenyl acrylate (BPOCPA) synthesized by condensation reaction of p-acryloyloxybenzoyl chloride (ABC) with 4-hydroxybenzophenone (HBP) by means of experimental and theoretical evidences. The spectroscopic properties of the compound are experimentally examined by Fourier transformation-infrared (FTIR) spectra (in the region 400-4000 cm(-1)) and nuclear magnetic resonance (NMR) chemical shifts (with a frequency of 400 MHz). For the theoretical studies, the optimized molecular structures, vibrational frequencies including infrared intensities and Raman activities, corresponding vibrational spectra interpreted with the aid of normal coordinate analysis based on scaled density functional force field, atomic charges, thermodynamic properties, (1)H and (13)C NMR chemical shifts, JCH and JCC coupling constants belonging to the BPOCPA compound are analyzed in the ground state by the way of the density functional theory (B3LYP) with the standard 6-311++G(d,p) level of theory for the first time. All the results obtained show that the calculated vibrational frequencies and chemical shifts are observed to be in good agreement with the available experimental findings. According to the comparison between experimental results and theoretical data, the calculation level chosen plays an important role in understanding of dynamics of the title compound studied in this work. The self-consistent field (SCF) energy of the molecule in six different solvent media is also analyzed at the same basis set by applying both the Onsager and Polarizable Continuum Model (PCM). It is found that the SCF energies deduced from the methods reduce with the enhancement of the solvent polarity as a consequence of the increment in the stability of the compound studied. Besides, the changes of the PCM calculations are found to be higher than those of the Onsager ones, confirming that the former method displays a more stable structure than latter model.

Conformational stability, vibrational spectra, molecular structure, NBO and HOMO-LUMO analysis of 5-nitro-2-furaldehyde oxime based on DFT calculations

The FTIR and FT-Raman spectra of 5-nitro-2-furaldehyde oxime (NFAO) have been recorded in the regions 4000-400 cm(-1) and 3500-50 cm(-1), respectively. The total energies of different conformations have been obtained from DFT (B3LYP) with 6-311++G(d,p) basis set calculations. The computational results identify the most stable conformer of NFAO as the C1 form. Utilizing the observed FTIR and FT-Raman data, a complete vibrational assignment and analysis of the fundamental modes of the compound were carried out. The optimum molecular geometry, harmonic vibrational frequencies, infrared intensities and Raman scattering activities, were calculated by density functional theory (DFT/B3LYP) method with 6-31+G(d,p) and 6-311++G(d,p) basis sets. The difference between the observed and scaled wavenumber values of most of the fundamentals is very small. A detailed interpretation of the infrared and Raman spectra of NFAO is also reported based on total energy distribution (TED). Stability of the molecule arising from hyperconjugative interactions, charge delocalization have been analyzed using natural bond orbital (NBO) analysis. Besides, molecular electrostatic potential (MEP), HOMO and LUMO analysis, and several thermodynamic properties were performed by the DFT method. Mulliken's net charges have been calculated and compared with the natural atomic charges. Ultraviolet-visible spectrum of the title molecule has also been calculated using TD-DFT method.

Molecular structure and spectroscopic analysis of 1,4-Bis(1-methyl-2-benzimidazolyl)benzene; XRD, FT-IR, dispersive-Raman, NMR and DFT studies

This study reports the structural characterization of a bis-benzimidazole derivative, 1,4-Bis(1-methyl-2-benzimidazolyl)benzene (BMBB), by using spectroscopic and quantum chemical methods. The BMBB molecule was synthesized under microwave conditions and was characterized by using single-crystal X-ray diffraction, FT-IR, dispersive Raman and NMR spectroscopies. The potential energy surface scan study was carried out for the conformation of the theoretical structure. Quantum chemical calculations of relative energies, molecular geometry, vibrational wavenumbers, frontier molecular orbitals, atomic charges and gauge including atomic orbital (GIAO) (1)H and (13)C-NMR chemical shifts of the compound were carried out by using density functional method (DFT) at B3LYP/6-311++G(d,p) theory level. The complete assignments of the vibrational modes were performed with DFT calculations combined with scaled quantum mechanics force field (SQMFF) methodology. A satisfactory consistency between the experimental and theoretical findings was obtained. On account of the relative energies, population analysis and XRD results, the most stable conformational form of the molecule was also determined.

FT-IR, FT-Raman, NMR studies and ab initio-HF, DFT-B3LYP vibrational analysis of 4-chloro-2-fluoroaniline

The Fourier transform infrared (FT-IR) and Fourier transform Raman (FT-Raman) spectra of 4-chloro-2-fluoroaniline (CFA) have been recorded and analyzed. The equilibrium geometry, bonding features and harmonic vibrational frequencies have been investigated with the help of ab initio and density functional theory (DFT) methods. The assignments of the vibrational spectra have been carried out with the help of normal coordinate analysis (NCA) following the scaled quantum mechanical force field methodology. The (1)H and (13)C nuclear magnetic resonance (NMR) chemical shifts of the molecule are calculated by the Gauge including atomic orbital (GIAO) method. The first order hyperpolarizability (β(0)) of this novel molecular system and related properties (β, α(0) and Δα) of CFA are calculated using B3LYP/6-311++G(d,p) and HF/6-311++G(d,p) methods on the finite-field approach. The calculated results also show that the CFA molecule might have microscopic nonlinear optical (NLO) behavior with non-zero values. Stability of the molecule arising from hyper conjugative interactions, charge delocalization has been analyzed using natural bond orbital (NBO) analysis. The result confirms the occurrence of intramolecular charge transfer (ICT) within the molecule. The HOMO-LUMO energies UV-vis spectral analysis and MEP are performed by B3LYP/6-311++G(d,p) approach. A detailed interpretation of the infrared and Raman spectra of CFA is also reported based on total energy distribution (TED). The difference between the observed and scaled wave number values of the most of the fundamentals is very small.

Theoretical investigations of α,α,α-trifluoro-3, -p and o-nitrotoluene by means of density functional theory

This study reports the optimized molecular structures, vibrational frequencies including Infrared intensities and Raman activities, corresponding vibrational assignments, (1)H and (13)C NMR chemical shifts, the magnitudes of the JCH and JCC coupling constants, Ultraviolet-visible (UV-vis) spectra, thermodynamic properties and atomic charges of the title compounds, α,α,α-trifluoro-3, -p and o-nitrotoluene, in the ground state by means of the density functional theory (DFT) with the standard B3LYP/6-311++G(d,p) method and basis set combination for the first time. Theoretical vibrational spectra were interpreted by normal coordinate analysis based on scaled density functional force field. The results show that the vibrational frequencies and chemical shifts calculated were obtained to be in good agreement with the experimental data. Based on the comparison between experimental results and theoretical data, the calculation level chosen is powerful approach for understanding the identification of all the molecules studied. In addition, not only were frontier molecular orbitals (HOMO and LUMO), molecular electrostatic potential (MEP) and electrostatic potential (ESP) simulated but also the dipole moment, softness, electronegativity, chemical hardness, electrophilicity index, transition state and energy band gap values were predicted. According to the investigations, all compounds were found to be useful to bond metallically and interact intermolecularly; however, the thermodynamic properties confirm that the α,α,α-trifluoro-p-nitrotoluene was more reactive and more polar than the others.

A characterization study on 2,6-dimethyl-4-nitropyridine N-oxide by density functional theory calculations

This study deals with the identification of a title compound, 2,6-dimethyl-4-nitropyridine N-oxide by means of theoretical calculations. The optimized molecular structures, vibrational frequencies, corresponding vibrational assignments, thermodynamic properties and atomic charges of the title compound in the ground state were evaluated using density functional theory (DFT) with the standard B3LYP/6-311G(d,p) method and basis set combination for the first time. Theoretical vibrational spectra were interpreted with the aid of normal coordinate analysis based on scaled density functional force field. The results show that the optimized geometric parameters (bond lengths and bond angles) and vibrational frequencies were observed to be in good agreement with the available experimental results. Based on the results of comparison between experimental results and theoretical data, the chosen calculation level is powerful approach for understanding the molecular structures and vibrational spectra of the 2,6-dimethyl-4-nitropyridine N-oxide. Moreover, we not only simulated frontier molecular orbitals (FMO) and molecular electrostatic potential (MEP) but also determined the transition state and energy band gap. Based on the investigations, the title compound is found to be useful to bond metallically and interact intermolecularly. Infrared intensities and Raman activities were also reported.

Experimental and theoretical studies on the identification of p-biphenyloxycarbonylphenyl acrylate

This study presents the identification of a title compound, p-biphenyloxycarbonylphenyl acrylate by means of experimental and theoretical evidences. The spectroscopic properties of the compound were experimentally investigated by Fourier transformation-infrared spectra (in the region 400-4000 cm(-1)) and nuclear magnetic resonance (NMR) chemical shifts (with a frequency of 400 MHz). Moreover, the optimized molecular structures, vibrational frequencies including infrared intensities and Raman activities, corresponding vibrational spectra interpreted with the aid of normal coordinate analysis based on scaled density functional force field, thermodynamic properties, atomic charges and ultraviolet-visible (UV-vis) spectra were analyzed utilizing ab initio Hartree-Fock (HF) and Density Functional Theory (B3LYP) methods at 6-31G(d,p) calculation level. It was found that the vibrational frequencies and chemical shifts obtained were shown to have a good agreement with available experimental results. We not only simulated frontier molecular orbitals (FMO) and molecular electrostatic potential (MEP) but also evaluated the transition state and energy band gap clearly.

Density functional theory study on the identification of 3-[(2-morpholinoethylimino)methyl]benzene-1,2-diol

This study deals with the identification of a title compound, 3-[(2-morpholinoethylimino)methyl]benzene-1,2-diol by means of quantum chemical calculations. The optimized molecular structures, vibrational frequencies and corresponding vibrational assignments, thermodynamic properties, charge analyses, nuclear magnetic resonance (NMR) chemical shifts and ultraviolet-visible (UV-vis) spectra of the title molecule in the ground state were evaluated using density functional theory (DFT) with the standard B3LYP/6-311++G(d,p) method and basis set combination for the first time. Theoretical vibrational spectra of the title compound were interpreted with the aid of normal coordinate analysis based on scaled density functional force field. The results show that the obtained optimized geometric parameters (bond lengths, bond angles and bond dihedrals) and vibrational frequencies were observed to be in good agreement with the available experimental results. Moreover, the calculations of the electronic spectra, (13)C and (1)H chemical shifts were compared with the experimental ones. Furthermore, we not only simulated the frontier molecular orbitals (FMO) and molecular electrostatic potential (MEP) but also determined the transition states and energy band gaps, as well. It was found that charge analyses supported the evidences of MEP. Infrared intensities and Raman activities were also reported.