Facile synthesis of multifunctional silver nanoparticles using mangrove plant Excoecaria agallocha L. for its antibacterial, antioxidant and cytotoxic effects.

The current study describes a simple, rapid and eco-friendly method for the synthesis of silver nanoparticles (AgNPs) using Excoecaria agallocha (E. agallocha) leaf extract as stabilizer, bioreductant and capping agent. Synthesized AgNPs were characterized by UV-Visible spectroscopy (UV-Vis), X-ray diffraction (XRD), fourier transform infrared (FT-IR) spectroscopy, field emission scanning electron microscopy (FESEM) and energy dispersive X-ray spectroscopy (EDX). Generation of AgNPs was initially confirmed with the color change from yellow to dark brown which produces intense absorbance spectra at 440 nm in UV-Vis spectroscopy without any shifting of peaks. Further, XRD pattern confirms that the synthesized AgNPs was face centered cubic (fcc) crystalline in structure with an average size of 20 nm. On the other hand, FTIR spectrum reveals that the active metabolites like water soluble phenolic compounds, flavonoids, methylene groups, amides and carboxylate groups. These active biocompounds plays a vital role in the reduction of Ag+ into their nanoscale values, it also acts as a stabilizing and surface functionalization agent. FESEM micrographs of synthesized AgNPs shows spherical and hexagonal shaped well dispersed particles in the dimension ranging between 23 and 42 nm. EDAX confirms the presence of silver (Ag) as the major constituent element without any impurities; also substantiate the stability of generated AgNPs. The biomedical insights of nanoparticles (NPs) were assessed through radical scavenging and antibacterial properties. Additionally, synthesized AgNPs was also exhibits an excellent cytotoxic effect against human breast carcinoma cell lines (MCF-7). This study proves that synthesized AgNPs can be developed as a potential nano-drug formulation to combat pathogenic disease and also for the expansion of breast cancer therapy.

Quantum chemical computations, vibrational spectroscopic studies, NLO and NBO/NLMO analysis of o-chlorobenzohydrazide.

The molecular vibrations of o-chlorobenzohydrazide (OCBH) have been investigated in polycrystalline sample, at room temperature, by recording Fourier transform infrared (FT-IR) and FT-Raman spectroscopies. The complete vibrational assignment and analysis of the fundamental modes was carried out using the experimental data and quantum chemical studies. The observed vibrational data were compared with the wavenumbers derived theoretically for the optimized geometry of the compound from the HF and DFT/B3LYP calculations employing 6-311++G(d,p) basis set. The (1)H and (13)C NMR chemical shifts have been simulated. Thermodynamic properties have been calculated at different temperatures. HOMO-LUMO energy gap has been calculated. The intramolecular contacts have been interpreted using Natural Bond Orbital (NBO) and Natural Localized Molecular Orbital (NLMO) analysis.

Vibrational spectra, monomer, dimer, NBO, HOMO, LUMO and NMR analyses of trans-4-hydroxy-L-proline.

This work presents the characterization of trans-4-hydroxy-L-proline (abbreviated as THLP) by quantum chemical calculations and spectral techniques. The spectroscopic properties were investigated by FT-IR, FT-Raman and (1)H and (13)C nuclear magnetic resonance (NMR) techniques. The FT-IR (4000-400 cm(-1)) and FT-Raman (3500-10 cm(-1)) spectra in the solid phase were recorded for THLP. The (1)H and (13)C NMR spectra were recorded in DMSO solution. The energies of THLP are obtained for all the eight conformers form density functional theory (DFT) with 6-311++G(d,p) basis set calculations. From the computational results, C1 conformer is identified as the most stable conformer of THLP. The theoretical wavenumbers were scaled and compared with experimental FT-IR and FT-Raman spectra. The complete assignments were performed on the basis of the experimental results and potential energy distribution (PED) of the vibrational modes, calculated with scaled quantum mechanical (SQM) method in terms of fundamental modes. The values of the total dipole moment (µ) and the first order hyperpolarizability (ß) of the investigated compound were computed using B3LYP/6-311++G(d,p) calculations. The calculated HOMO-LUMO energies reveal charges transfer occurs within the molecule. The isotropic chemical shift computed by (1)H and (13)C NMR chemical shifts of the THLF, calculated using the gauge invariant atomic orbital (GIAO) method also shows good agreement with experimental observations.

Spectroscopic (FTIR, FT-Raman, 13C and 1H NMR) investigation, molecular electrostatic potential, polarizability and first-order hyperpolarizability, FMO and NBO analysis of 1-methyl-2-imidazolethiol.

In this work, experimental and theoretical study on the molecular structure and vibrational spectra of 1-methyl-2-imidazolethiol (MIME) were presented. The vibrational frequencies of the title compound were obtained theoretically by ab initio HF and DFT (B3LYP/LSDA) employing 6-311G (d,p) and 6-311++G(d,p) basis sets and compared with experimental spectral bands (FTIR and FT-Raman). The thermodynamic properties of the studied compound have been computed at different temperatures. The atomic charges and charge delocalization of the molecule have been analyzed by natural bond orbital (NBO) analysis. The reactivity sites are identified by mapping the molecular electrostatic potential (MESP) surface. Electronic properties HOMO and LUMO energies were measured by time-dependent TD-DFT approach. Besides, (13)C and (1)H nuclear magnetic resonance (NMR) chemical shifts of the molecule in chloroform solvent calculated using the Gauge-Independent Atomic Orbital (GIAO) method are found to be in good agreement with experimental values.

Conformational stability, vibrational spectra, HOMO-LUMO and NBO analysis of 1,3,4-thiadiazolidine-2,5-dithione with experimental (FT-IR and FT-Raman) techniques and scaled quantum mechanical calculations.

The experimental and theoretical study on the structure and vibrations of 1,3,4-thiadiazolidine-2,5-dithione (TDZD) is presented. The FT-IR spectra (4000-400 cm(-1)) and the FT-Raman spectra (4000-50 cm(-1)) of the title molecule have been recorded. The energies of TDZD were obtained for all the possible four conformers from HF and DFT with 6-311G(d,p) and 6-311++G(d,p) basis set calculations. From the computational results, conformer C4 is identified as the most stable conformers of TDZD. The spectroscopic and theoretical results are compared with the corresponding properties for TDZD of C4 conformer. The temperature dependence of thermodynamic properties has been analyzed. Molecular stability and bond strength were investigated by applying the natural bond orbital analysis (NBO). The calculated HOMO and LUMO energies show that charge transfer occurs in the molecules. Information about the size, shape, charge density distribution, and site of chemical reactivity of the molecules has been obtained by mapping electron density isosurface with electrostatic potential (ESP). The dipole moment (λ) and polarizability (α), anisotropy polarizability (Δα) and first hyperpolarizability (ßtotal) of the molecule have been reported.

Quantum chemical calculations, vibrational studies, HOMO-LUMO and NBO/NLMO analysis of 2-bromo-5-nitrothiazole.

The complete vibrational assignment and analysis of the fundamental modes of 2-bromo-5-nitrothiazole (BNT) was carried out using the experimental FTIR and FT-Raman data and quantum chemical studies. The observed vibrational data were compared with the wavenumbers derived theoretically for the optimized geometry of the compound from the ab initio HF and DFT-B3LYP gradient calculations employing 6-311++G(d,p) basis set. Thermodynamic properties like entropy, heat capacity and zero point energy have been calculated for the molecule. HOMO-LUMO energy gap has been calculated. The intramolecular contacts have been interpreted using Natural Bond Orbital (NBO) and Natural Localized Molecular Orbital (NLMO) analysis. Important non-linear properties such as electric dipole moment and first hyperpolarizability of BNT have been computed using B3LYP quantum chemical calculation.

Ab initio, density functional computations, FT-IR, FT-Raman and molecular geometry of 4-morpholine carbonitrile.

The 4-morpholine carbonitrile (4MC) was investigated by vibrational spectroscopy and quantum chemical methods. The solid phase FT-IR and FT-Raman spectra were recorded in the region 4000-400 cm(-1) and 3500-50 cm(-1), respectively. The molecular geometry and vibrational frequencies of 4MC have been calculated in the ground state by using the ab initio Hartree-Fock and density functional method (B3LYP) with 6-311++G(d, p) basis set. The observed and calculated frequencies are found to be in good agreement. The calculated HOMO and LUMO energies show the charge transfer occurs within the molecule. Stability of the molecule arising from hyper conjugative interactions and charge delocalization has been analyzed using natural bond orbital (NBO) analysis. The theoretical FT-IR and FT-Raman spectra for the title compound have also been constructed.

Experimental and theoretical spectroscopic studies, HOMO-LUMO, NBO and NLMO analysis of 3,5-dibromo-2,6-dimethoxy pyridine.

The molecular vibrations of 3,5-dibromo-2,6-dimethoxy pyridine (DBDMP) have been investigated in polycrystalline sample, at room temperature, by Fourier transform infrared (FT-IR) and FT-Raman spectroscopies. The vibrational frequencies of the fundamental modes of the compound have been precisely assigned and theoretical results were compared with the experimental vibrations. Theoretical information on the optimized geometry, harmonic vibrational frequencies, infrared and Raman activities were obtained by means of ab initio and density functional theory (DFT) gradient calculations, using 6-311++G(d,p) basis set. Thermodynamic properties like entropy, heat capacity and zero point energy have been calculated for the molecule. HOMO-LUMO energy gap has been calculated. The intramolecular contacts have been interpreted using Natural Bond Orbital (NBO) and Natural Localized Molecular Orbital (NLMO) analysis. The Molecular Electrostatic Potential (MEP) analysis reveals the sites for electrophilic attack and nucleophilic reactions in the molecule.

Density functional theory study on characterization of 3-chloro-1,2-benzisothiazole.

The FT-IR and FT-Raman spectra of 3-chloro-1,2-benzisothiazole (CBT) have been recorded and analyzed. Theoretical information on the optimized geometry, harmonic vibrational frequencies, infrared and Raman intensities were obtained by means of density functional theory (DFT) gradient calculations, using 6-311++G(d,p) basis set. Mulliken population analysis shows charge distribution on the molecule. Thermodynamic properties like entropy, heat capacity, zero point energy have been calculated for the molecule. The calculated HOMO and LUMO energies show the charge transfer occurs within the molecule. Stability of the molecule has been analyzed using Natural Bond Orbital (NBO) and Natural Localized Molecular Orbital (NLMO) analysis. The results of the calculations were applied to simulated spectra of the title compound, which show the excellent agreement with the observed spectra.

FT-IR, FT-Raman, ab initio and DFT studies, HOMO-LUMO and NBO analysis of 3-amino-5-mercapto-1,2,4-triazole.

The molecular vibrations of 3-amino-5-mercapto-1,2,4-triazole (AMT) have been investigated in polycrystalline sample, at room temperature, by Fourier transform infrared (FT-IR) and FT-Raman spectroscopies. A detailed vibrational spectral analysis has been carried out and assignments of the fundamental modes have been proposed on the basis of peak positions and relative frequencies, atomic charges, HOMO-LUMO energies and several thermodynamic properties in the ground state were calculated using ab initio Hartree-Fock (HF) and Density Functional Theory, (B3LYP) with 6-311G(d,p) and 6-311++G(d,p) basis sets. With the aid of scaling procedures, observed wave numbers in FT-IR and FT-Raman spectra were analyzed and assigned to different normal modes of the molecule. Most of the modes have wave numbers in the expected range. The theoretical IR and Raman spectra have also been constructed. Natural Bond Orbital (NBO) study explains charge delocalization of the molecule.

FTIR, FT-Raman, scaled quantum chemical studies of the structure and vibrational spectra of 1,5-dinitronaphthalene.

The solid phase FTIR and FT-Raman spectra of 1,5-dinitronaphthalene (DNN) have been recorded in the regions 4000-50 and 3500-100cm(-1), respectively. The spectra were interpreted with the aid of normal coordinate analysis following full structure optimization and force field calculation based on density functional theory using standard B3LYP/6-31G* and B3LYP/6-311+G** methods and basis set combinations and was scaled using various scale factors yielding fairly good agreement between observed and calculated frequencies. Based on the present good quality scaled quantum mechanical force field, a reliable description of the fundamentals was provided and the assignments have been proposed with the help of normal coordinate analysis. The infrared and Raman spectra were also predicted from the calculated intensities. Comparison of the simulated spectra with the experimental spectra provides important information about the ability of the computational method to describe the vibrational modes.

Analysis of vibrational spectra of 4-amino-2,6-dichloropyridine and 2-chloro-3,5-dinitropyridine based on density functional theory calculations.

This work deals with the vibrational spectroscopy of 4-amino-2,6-dichloropyridine (ADCP) and 2-chloro-3,5-dinitropyridine (CDNP) by means of quantum chemical calculations. The mid and far FTIR and FT-Raman spectra were measured in the condensed state. The fundamental vibrational frequencies and intensity of vibrational bands were evaluated using density functional theory (DFT) with the standard B3LYP/6-31G(*) and B3LYP/6-311+G(**) methods and basis set combinations, and was scaled using various scale factors which yields a good agreement between observed and calculated frequencies. The vibrational spectra were interpreted with the aid of normal coordinate analysis based on scaled density functional force field. The results of the calculations were applied to simulated infrared and Raman spectra of the title compounds, which showed excellent agreement with the observed spectra.

Density functional theory study of vibrational spectra, and assignment of fundamental vibrational modes of succinimide and N-bromosuccinimide.

This work deals with the vibrational spectroscopy of succinimide and N-bromosuccinimide. The mid and far FTIR and FT-Raman spectra were measured in the condensed state. The fundamental vibrational frequencies and intensity of vibrational bands were evaluated using density functional theory (DFT) using standard B3LYP/6-31G(*) and B3LYP/6-311+G(**) methods and basis set combinations. The vibrational spectra were interpreted, with the aid of normal coordinate analysis based on a scaled quantum mechanical force field. The infrared and Raman spectra were also predicted from the calculated intensities. Comparison of simulated spectra with the experimental spectra provides important information about the ability of the computational method to describe the vibrational modes. Unambiguous vibrational assignment of all the fundamentals were made using the total energy distribution (TED).

Vibrational analysis of 1,4-diaminoanthraquinone and 1,5-dichloroanthraquinone. A joint FTIR, FT-Raman and scaled quantum mechanical study.

This work deals with the vibrational spectroscopy of 1,4-diaminoanthraquinone (1,4-DAAQ) and 1,5-dichloroanthraquinone (1,5-DCAQ). The mid and far FTIR and FT-Raman spectra were measured in the condensed state. The fundamental vibrational frequencies and intensity of the vibrational bands were evaluated using density functional theory (DFT) with the B3LYP functional and 6-31G* basis set. The vibrational spectra were interpreted with the aid of normal coordinate analysis based on a scaled quantum mechanical force field. The infrared and Raman spectra were also predicted from the calculated intensities. Unambiguous vibrational assignment of all the fundamentals were made using the potential energy distribution (PED).

Density functional theory calculations and vibrational spectra of 3,5-dibromopyridine and 3,5-dichloro-2,4,6-trifluoropyridine.

The solid phase mid FTIR and FT-Raman spectra of 3,5-dibromopyridine (3,5-DBP) and 3,5-dichloro-2,4,6-trifluoropyridine (3,5-DCTFP) have been recorded in the regions 4000-400 cm(-1) and 3500-100 cm(-1), respectively. The spectra were interpreted with the help of normal coordinate analysis (NCA) following full structure optimisation and force field calculations based on the density functional theory (DFT) using the standard B3LYP/6-31G( *) method and basis set combination. The results of the calculations are applied to stimulate infrared and Raman spectra of the title compounds which showed excellent agreement with the observed spectra.

Hydrogen bonding and molecular vibrations of 3,5-diamino-1,2,4-triazole.

This work deals with the analysis of hydrogen bonding and the vibrational spectroscopy of 3,5-diamino-1,2,4-triazole by means of quantum chemical calculations. The mid and far FTIR and FT-Raman spectra were measured in the condensed state. The fundamental vibrational frequencies were calculated under different possible symmetries by applying the density functional theory with the B3LYP functional and the 6-31G* basis set. The results of the calculations obtained under C(2) symmetry produces the global minimum on the potential energy surface. The vibrational spectra were interpreted with the aid of normal coordinate analysis based on scaled density functional force field. The infrared and Raman spectra were also predicted from the calculated intensities.

FT Raman and FT-IR spectral studies of 3-mercapto-1,2,4-triazole.

The FT-IR and FT Raman spectra of 3-mercapto-1,2,4-triazole have been recorded. The observed frequencies were assigned to various modes of vibrations on the basis of normal coordinate calculations, assuming Cs point group symmetry. The potential energy distribution associated with normal modes is also reported here. The assignment of fundamental vibrations agrees well with the calculated frequencies.