Fourier transform-infrared and Raman spectra, ab initio calculations and assignments for 6-methyl-4-bromomethylcoumarin

2H-Pyrano[3,2-c]chromene-2,5(6H)-diones: Synthesis, Characterization, Photophysical and Redox Studies for Potential Optoelectronic Applications

Herein, we report the preparation of 2H-pyrano[3,2-c]chromene-2,5(6H)-diones 3a-x by reacting 4-hydroxycoumarins 1a-b with Baylis-Hillman adducts 2a-w having electron releasing or electron withdrawing groups on benzyl ring of the pyranochromene moiety and study of their photophysical properties. The study of optical and electrochemical properties of the prepared compounds reveals that the electron releasing and electron withdrawing groups has not much impact on ground and excited state electronic behavior on pyranochromene moiety. The density functional theory suggests the highest occupied molecular orbital and lowest unoccupied molecular orbitals spread on coumarin moiety of pyranochromene unit. Further, these compounds are thermally stable (up to 200 °C) and lead to blue or green emission that should facilitate the development of organic light emitting diodes (OLEDs).

Combined experimental and theoretical studies on 4-(2-hydroxy-3-morpholin-4-yl-propoxy)-chromen-2-one

The FTIR, UV–Vis and NMR spectra of 4-(2-hydroxy-3-morpholin-4-yl-propoxy)-chromen-2-one (4-HMPC) have been recorded and analyzed. The optimized geometry and harmonic vibrational frequencies of 4-HMPC were obtained by the Hartree–Fock (HF) and density functional theory (DFT) using B3LYP functional with 6-311[Formula: see text]G basis set. The 1H and [Formula: see text]C NMR chemical shifts were calculated by the GIAO method in chloroform. The absorption spectra of 4-HMPC were computed in ethanol and water solutions using TD-B3LYP/6-311[Formula: see text]G(d,p) approach. The correlation of theoretical and experimental results provides a detailed description of the structural and physicochemical properties of the molecule. The results obtained from the studies of HOMO and LUMO were used to calculate the conceptual-DFT-based global reactivity descriptors such as electronic chemical potential, electronegativity, chemical hardness, global softness and electrophilicity index of the compound.

Combined spectroscopic and DFT studies on 6-bromo-4-chloro-3-formyl coumarin

The FTIR and FT-Raman spectra of 6-bromo-4-chloro-3-formyl coumarin (6B4C3FC) have been recorded in the region 4000-400 and 4000-100 cm(-1), respectively. The optimized geometry, frequency and intensity of the vibrational bands were obtained by the density functional theory (DFT) using 6-31G(d,p) basis set. The harmonic vibrational frequencies were scaled and compared with experimental values. The observed and the calculated frequencies were found to be in good agreement. The UV-Visible spectrum was also recorded and compared with the theoretical values. The calculated HOMO and LUMO energies show that charge transfer occurs within molecule. The first order hyperpolarizability (β0) of 6B4C3FC is 21 times greater than that of urea. Stability of the molecule arising from hyperconjugative interactions, charge delocalization have been analyzed using natural bond orbital (NBO) analysis. Information about the charge density distribution of the molecule and its chemical reactivity has been obtained by mapping molecular electrostatic potential surface. In addition, the non-linear optical properties were discussed from the dipole moment values and the excitation wavelength in the UV-Visible region.

Dispersive and FT-Raman spectroscopic methods in food analysis

Raman spectroscopy is a powerful technique for molecular analysis of food samples.

Vibrational spectra, structural conformations, scaled quantum chemical calculations and NBO analysis of 3-acetyl-7-methoxycoumarin

The powder form NIR-FT Raman and FT-IR spectra of 3-acetyl-7-methoxycoumarin (3A7MC) have been recorded in the regions 4000-400 and 3500-100 cm(-1), respectively. The equilibrium geometry, vibrational frequencies, band intensities, NMR spectra, NBO analysis and UV-Vis spectral studies of the most stable conformer have been calculated by density functional B3LYP method with the 6-311G(d,p) basis set. A complete vibrational analysis has been attempted on the basis of experimental infrared and Raman spectra, the calculated wavenumber and intensity of the vibrational bands and the potential energy distribution over the internal coordinates. Information about the size, shape, charge density distribution and site of chemical reactivity of the molecules has been obtained by mapping the electron density isosurface with electrostatic potential surfaces (ESP). Natural bond orbital analysis has been carried out to understand the nature of different interactions responsible for the electron delocalization and the intramolecular charge transfer between the orbitals (n→π(∗), n→σ(∗), π→π(∗)).

FT-IR, FT-Raman and UV-Vis spectra and DFT calculations of 3-cyano-4-methylcoumarin

The vibrational and electronic spectra of 3-cyano-4-methylcoumarin (3C4MC) are reported and discussed. In this work the structural properties, vibrational frequencies and electronic spectra of 3C4MC have been investigated extensively using density functional theory (DFT) employing B3LYP exchange correlation with the normal basis level 6-31G(d,p). NBO and HOMO, LUMO analysis has been carried out. The geometries and normal modes of vibrations obtained from B3LYP calculations are in good agreement with the experimentally observed data.

The spectroscopic properties of anticancer drug Apigenin investigated by using DFT calculations, FT-IR, FT-Raman and NMR analysis

The FT-Raman and FT-Infrared spectra of solid Apigenin sample were measured in order to elucidate the spectroscopic properties of title molecule in the spectral range of 3500-50 cm(-1) and 4000-400 cm(-1), respectively. The recorded FT-IR and FT-Raman spectral measurements favor the calculated (by B3LYP/6-31G(d,p) method) structural parameters which are further supported by spectral simulation. Additional support is given by the collected (1)H and (13)C NMR spectra recorded with the sample dissolved in DMSO. The predicted chemical shifts at the B3LYP/6-31G(d) level obtained using the Gauge-Invariant Atomic Orbitals (GIAO) method with and without inclusion of solvent using the Polarizable Continuum Model (PCM). By using TD-DFT method, electronic absorption spectra of the title compound have been predicted and a good agreement with the TD-DFT method and the experimental one is determined. The UV-visible absorption spectra of the compound that dissolved in Ethanol, Methanol and DMSO were recorded in the range of 800-200 nm. The formation of hydrogen bond and the most possible interaction are explained using natural bond orbital (NBO) analysis. In addition, the molecular electrostatic potential (MEP), frontier molecular orbitals (FMO) analysis and atomic charges of the title compound were investigated using theoretical calculations. The results are discussed herein and compared with similar molecules whenever appropriate.

Density functional theory, comparative vibrational spectroscopic studies, NBO, HOMO-LUMO analyses and thermodynamic functions of N-(bromomethyl)phthalimide and N-(chloromethyl)phthalimide

Quantum mechanical calculations of energies, geometries, and vibrational wavenumbers of N-(bromomethyl)phthalimide and N-(chloromethyl)phthalimide are carried out using density functional theory (DFT/B3LYP) method with 6-31G and 6-311G(d,p) basis sets. The optimized geometrical parameters obtained by B3LYP method show good agreement with experimental data. 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 N-(bromomethyl)phthalimide and N-(chloromethyl)phthalimide was also reported. The calculated HOMO and LUMO energies show that charge transfer occurs in the molecules. The thermodynamic functions of N-(bromomethyl)phthalimide and N-(chloromethyl)phthalimide have been performed at B3LYP/6-31G and B3LYP/6-311G(d,p) basis sets. The theoretical spectrograms for FT-IR and FT-Raman spectra of N-(bromomethyl)phthalimide and N-(chloromethyl)phthalimide have also been constructed.

DFT-based molecular modeling, NBO analysis and vibrational spectroscopic study of 3-(bromoacetyl)coumarin

The NIR-FT Raman and FT-IR spectra of 3-(bromoacetyl)coumarin (BAC) molecule have been recorded and analyzed. Density functional theory (DFT) calculation of two BAC conformers has been performed to find the optimized structures and computed vibrational wavenumbers of the most stable one. The obtained vibrational wavenumbers and optimized geometric parameters were seen to be in good agreement with the experimental data. Characteristic vibrational bands of the pyrone ring and methylene and carbonyl groups have been identified. The lowering of HOMO-LUMO energy gap clearly explains the charge transfer interactions taking place within the molecule.

Vibrational spectroscopic investigation and DFT studies on 2,2',4,4'-tetrabromodiphenyl ether

In the present work, the infrared (IR) and Raman spectra of 2,2',4,4'-tetrabromodiphenyl ether have been measured in the ranges of 400-4000cm(-1) and 100-4000cm(-1). The geometry optimized by the density functional theory Becke-3-Lee-Yang-Parr (B3LYP) method with the 6-31G(d) basis set was in good agreement with the experimental data of analogues. The results have shown that the dihedral angle of biphenyl ether significantly increases with the addition of bromine substitution. The vibrational frequencies were evaluated by the B3LYP method in conjunction with basis sets of 6-31G(d), 6-31G(2df,p), 6-311+G(d,p), 6-311G+(2df,p), and 6-311++G(d,p), separately. The scaled frequencies resulted in excellent agreement with the observed spectral patterns. The correlation analysis and statistical comparisons indicated that the basis sets larger than 6-31G(d) resulted in no significant improvement in the accuracy of the vibration frequencies. The detailed assignments were performed according to the calculated results for B3LYP/6-31G(d) and then compared with those from a previous study on 4,4'-dibromodiphenyl ether. The absence of coupling of C-O stretching and adjacent C-H in-plane deformation indicated a strong steric effect owing to the ortho bromine atoms in the title compound. Moreover, the quantum theory of atoms in molecules (QTAIM) and the Moller-Plesset second-order perturbation (MP2) method are applied to exclude the possible formation of intramolecular non-covalent interactions such as Br...Br and C-H...Br.

Vibrational spectra, normal modes, ab initio and DFT calculations for 6-Chloro- and 7-Chloro-4-bromomethylcoumarins

Vibration spectral measurements - Infrared (4000-400 cm(-1)) and Raman (3500-50 cm(-1)) spectra - have been made for the solid samples of 6-Chloro- and 7-Chloro-4-bromomethylcoumarins. Ground electronic state energies, equilibrium geometries, harmonic vibrational spectra and normal modes have been computed using ab initio - RHF/6-31G* - and DFT - B3LYP/6-31G* levels of theory. The optimization yielded three structures for each molecule, with one being a transition state structure. Of the remaining two conformers, one belongs to C(s) symmetry and the other belongs to C(1), the latter being the most stable one. The optimized dihedral angle for -CH(2)Br group is 111 degrees in agreement with X-ray diffraction results reported for the similar molecular systems. Assignment of all the observed spectral bands has been proposed. The absorptions show band pattern revealing isomer characteristics and vibrational coupling in varying degrees; the Raman spectra show structural changes associated with the rings as well as lattice modes.

Vibrational spectroscopy investigation using ab initio and density functional theory on 3'-chloropropiophenone and 3'-nitropropiophenone

The FTIR and FT Raman spectra of 3'-chloropropiophenone and 3'-nitropropiophenone have been recorded in the regions 4000-400 and 3500-100 cm(-1) respectively. The optimized geometry, frequency and intensity of the vibrational bands of 3'-chloropropiophenone and 3'-nitropropiophenone were obtained by ab initio and DFT levels of theory with complete relaxation in the potential energy surface using 6-31G (d,p) basis set. A complete vibrational assignment aided by the theoretical harmonic frequency analysis has been proposed. The harmonic vibrational frequencies calculated have been compared with experimental FTIR and FT Raman spectra. The observed and the calculated frequencies are found to be in good agreement. The experimental spectra also coincide satisfactorily with those of theoretically constructed simulated spectrograms.

Vibrational assignments for 7-methyl-4-bromomethylcoumarin, as aided by RHF and B3LYP/6-31G* calculations

Infrared (4000-400 cm(-1)) and Raman (3500-50 cm(-1)) spectral measurements have been made for the solid sample of 7-methyl-4-bromomethylcoumarin. Electronic structure calculations at RHF/6-31G* and B3LYP/6-31G* levels of theory have been performed, giving equilibrium geometries, harmonic vibrational spectra and normal modes. Different orientations of bromomethyl group have yielded only two conformers, of which the most stable one lying lower from the other conformer by approximately 7.99 kJ/mol, is non-planar with no symmetry. A complete assignment of the vibrational modes, aided by the calculations, has been proposed. Coupled vibrations are manifest in many modes. Some spectral features, compared to 6-methyl-4-bromomethylcoumarin, show changes across both IR and Raman spectra, involving mainly skeletal vibrations, and to a lesser degree, methyl and bromomethyl vibrations. Low-frequency vibrations below 150 cm(-1) are assigned to lattice modes.

Vibrational spectroscopy investigation using ab initio and density functional theory on p-anisaldehyde

The FTIR and FT Raman spectra of p-anisaldehyde has been recorded in the regions 4,000-400 and 3,500-100 cm(-1), respectively. The optimized geometry, frequency and intensity of the vibrational bands of p-anisaldehyde were obtained by ab initio and DFT levels of theory with complete relaxation in the potential energy surface using 6-31G(d,p) basis set. A complete vibrational assignment aided by the theoretical harmonic frequency analysis has been proposed. The harmonic vibrational frequencies calculated have been compared with experimental FTIR and FT Raman spectra. The observed and the calculated frequencies are found to be in good agreement. The experimental spectra also coincide satisfactorily with those of theoretically constructed bar type spectrograms.

Vibrational assignments and electronic structure calculations for 3-acetylcoumarin

Laser Raman (3500-50 cm(-1)) and IR (4000-400 cm(-1)) spectral measurements have been made on the laboratory prepared solid 3-acetylcoumarin. Molecular electronic energy, equilibrium geometrical structure and harmonic vibrational spectra have been computed at the RHF/6-31G(d,p) and B3LYP/6-31G(d,p) levels of theory. A complete vibrational assignment aided by the theoretical harmonic frequency analysis has been proposed. The B3LYP/6-31G(d,p) geometrical parameters, and frequencies of the C=O in the pyrone and acetyl group are in good agreement with experiment. The difference in the frequencies due to the two carbonyl groups, 50 cm(-1), which is attributed to the conjugation effect, is accounted for by the B3LYP to be 56cm(-1).