Investigation on Vibrational Spectra and Structures of 4-Mercaptopyridine Monomer and Its Dihydrate

The optimized molecular structures and vibrational frequencies of 4-mercaptopyridine（4MPY） monomer and its dihydrate were studied by means of the density functional theory（ DFT）, viz. B3LYP method with the 6-311 ＋ ＋ G （d,p） basis set. On the basis of the calculations, the assignments of the vibrational spectra of the monomer and the dihydrate were performed, and so were investigated the changes in the structure and the vibrational spectrum of the di- hydrate as well as the intermolecular force resulting in the formation of the dihydrate. The calculated results show that each of the water molecule planes is vertical to the pyridine ring plane in the dihydrate that is formed via the H-bonds between 4MPY and water molecules. Furthermore, the structure and the vibrational spectrum of 4MPY can be considerably affected by the water molecules.

Analysis of vibrational spectra of nano-bio molecules: Application to metalloporphrins

In this paper, we have applied the Lie algebraic model to nano-bio molecules to determine the vibrational spectra of different stretching and bending vibrational modes. The determined vibrational energy levels by the Lie algebraic model are compared with the experimental data. The results from the theoretical mode[ are consistent with the experimental data. The vibrational energy levels are clustering in the excited states.

Ro-vibrational Spectra of the Simplest Deuterated Criegee Intermediate CD2OO

Criegee intermediates are of signi cance in the atmospheric chemistry.In this work,the rovibrational spectra of the simplest deuterated Criegee intermediate,CD2OO,were studied by a vibrational self-consistent eld/virtual con guration interaction(VSCF/VCI)method based on a nine-dimensional accurate potential energy surface and dipole surface for its ground electronic state.The calculated fundamental vibrational frequencies and rotational constants are in excellent agreement with the available experimental results.These data are useful for further spectroscopic studies of CD2OO.Especially,the rotational constants for excited vibrational levels are essential for experimental spectral assignments.However,the infrared intensities from di erent resources,including the current computation,the experiment,and previous calculations at the NEVPT2 and B3LYP levels,deviate signi cantly.

Vibrational spectra and intramolecular vibrational redistribution in methane and its isotopomers

An improved U（2） algebraic model is introduced to study the stretching and bending vibrational spectra of methane and its isotopomers.The algebraic model with fewer parameters reproduces the experimental spectra with good precision.Moreover,the obtained parameters describe well the correct behavior of isotopic substitution.It is shown that the Fermi resonance leads to a very fast intramolecular vibrational redistribution among stretches and bends.

Theoretical Study on the Structures, Vibrational Spectra, and the Nature of the Intermediate Hydrogen Bond of Schiff Bases

Semi-empirical method PM3 was used to study the geometry and vibrational spectrum of N-(2-hydroxy-l-naphthyl-methylene)-l-pyrenamine (NPY) with the intermediate hydrogen bond. Results are comparable to experimentations. Based on results of both NPY and its model, N-(2-hydroxy-l-naphthyl-methylene)aniline, it was found that the N-(2-hydroxy-l-naphthyl-methylene) group is principally responsible for the special hydrogen bonding through conjugation effect.

Theoretical Study on the Structure and Vibrational Spectra for 4-methyl-3-penten-2-one

Density functional theory BLYP (using Becke's and Lee-Yang-Parr's correlation functionals), nb initio Hartree-Fock (HF) and hybrid DFT/HF B3LYP calculations were carried out to study the structure and vibrational spectra of 4-methyl-3-penten-2-one. The BLYP/6-31G* and scaled HF/6-31G* frequencies correspond well with each other and with available experimental assignment of the functional vibrational modes.

Laser Linewidth and Spectral Resolution in Infrared Scanning Sum Frequency Generation Vibrational Spectroscopy System

Sum frequency generation vibrational spectroscopy （SFG-VS） is a robust technique for inter- facial investigation at molecular level. The performance of SFG-VS mostly depends on the spectral resolution of the SFG system. In this research, a simplified function was deduced to calculate the spectral resolution of picosecond SFG system and the lineshape of SFG spectra based on the Guassian shaped functions of IR beam and visible beam. The function indicates that the lineshpe of SFG spectra from nonresonant samples can be calculated by the Guassian widths of both IR beam and visible beam. And the Voigt lineshape of SFG spectra from vibrational resonant samples can be calculated by the Homogeneous broadening （Lorentzian width） and Inhomogeneous broadening （Guassian width） of vibrational modes, as well as the Guassian widths of both IR beam and visible beam. Such functions were also applied to verify the spectral resolution of the polarization-resolved and frequency-resolved picosecond SFG-VS system which was developed by our group recently. It is shown that the linewidths of IR beams that generated from current laser system are about 1.5 cm-1. The calculated spectral resolution of current picosecond IR scanning SFG-VS system is about 4.6 cm-1, which is consist with he spctral resolution shown in the spectra of cholesterol monolayer （3.5-5 cm-1）.

Molecular structure and vibrational spectra of phenobaraitone by density functional theory and ab initio hartree-Fock calculations

Quantum chemistry calculations have been performed using Gaussian03 program to compute optimized geometry,harmonic vibrational frequency along with intensities in IR and Raman spectra at RHF/6-31++G^(**)and B3LYP/6-31++G^(**)levels for phenobarbitone(C12H12N2O3)in the ground state.The scaled harmonic vibrational frequencies have been compared with experimental FT-IR and FT-Raman spectra.Theoretical vibrational spectra of the title compound were interpreted by means of potential energy distributions(PEDs)using MOLVIB program.A detailed interpretation of the infrared spectra of the title compound is reported.On the basis of the agreement between the calculated and observed results,the assignments of fundamental vibrational modes of phenobarbitone were examined and some assignments were proposed.The theoretical spectrograms for FT-IR and FT-Raman spectra of the title compound have been constructed.

Studies on nitramide and its methyl derivatives with ab initio calculations——Ⅳ.The harmonic force field and vibrational spectra of dimethylnitramine and its isotopic derivatives

The complete harmonic vibrational force field of dimethylnitramine has been calculated at the Hartree-Fock level using 4-21G basis set.The harmonic force field was then scaled with scale factors previously derived from N-methylnitramine,and the vibrational spectrum of dimethylnitramine was computed.This apriori prediction,made with no reference to observations on dimethylnitramine, agrees with the experimental IR spectrum in gas phase with a mean deviation of 8.4 cm^(-1).Some of the scale factors were reoptimized by fitting of the computed force field to experimental data.The new set of scale factors reduced the mean deviation to 4.5 cm^(-1),and was used to predict the vibrational spectrum of deuterated form of dimethylnitramine(-6D).Dipole moment derivatives were also cal- culated and used to predict infrared intensities which are comparable with experimental values.

Vibrational transition spectra of H_2^+ in a strong magnetic field

Vibrational transition spectra of H2＋ in an ultra-strong magnetic field are determined. The validity of Born- Oppenheimer approximation is analyzed based on one-center method and B-spline basis sets. It is shown that Born- Oppenheimer approximation is reliable for the investigation on the ground state and low excited states of H2＋ subjected to the strong magnetic field. Furthermore, it is found that the vibrational transition spectra from lσg, lπu, and 1δg states lie in infrared, visible, and ultraviolet ranges with increasing magnetic field strength.

THE VIBRATIONAL RAMAN SPECTRA AND PHOTON—INDUCED OXIDATION PHENOMENA OF PURIFIED SOLID FILMS OF C_(60)

The vibrational Raman spectra have been obtained for purified solid films C_(60). Three bands were observed out of the total of 10 that were theoretically predicted. Some phenomena which may be due to photon-induced oxidation in the vibrational Raman measuring were observed.

NMR Parameters and Vibrational Investigation of 2-Dicyanovinyl-5-(4-ethoxyphenyl) thiophene by ab initio HF and DFT Calculations

Optimized geometry and harmonic vibrational frequency of 2-dicyanovinyl-5-（4- ethoxyphenyl）thiophene （C16Hj2N2OS） are calculated at the HF/6-31＋＋G（d,p） and B3LYP/6- 311 ＋＋G（d,p） levels. Mulliken charges in the ground state are also calculated. The research shows the presence of intermolecular interaction in the title compound. The scaled harmonic vibrational frequencies have been compared with experimental FT-IR spectra. A detailed interpretation of the infrared spectra of the title compound is reported. The theoretical spectrograms for IR spectra of the title compound have been constructed, The isotropic chemical shift computed by 13C and 1H NMR analyses also shows good agreement with the experimental observations.

Structural and Vibrational Study of 2-（Quinolin-8-yloxy）-Acetic Acid based on FT-IR-Raman Spectroscopy and DFT Calculations

We have prepared the 2-（quinolin-8-yloxy）-acetic acid and characterized it by infrared and Raman spectroscopies in the solid phase. The Density Functional Theory （DFT） method, together with the 6-31G^＊ and 6-311＋＋ G^＊＊ basis sets, show that three stable molecules, for the anhydrous and monohydrated compounds were theoretically determined in the gas phase, and that probably the two more stable conformations are present in the solid phase of the monohydrated compound. The harmonic vibrational wavenumbers for the optimized geometries were calculated at B3LYP/6-31G^＊and B3LYP/6-311＋＋G^＊＊ levels. For a complete assignment of all the observed bands in the vibrational spectra the DFT calculations were combined with Pulay＇s scaled quantum mechanical force field （SQMFF） methodology in order to fit the theoretical Wavenumber values to the experimental ones. The characteristics of the electronic delocalization of all structures of both forms were performed by using natural bond orbital （NBO）, while the corresponding topological properties of electronic charge density are analysed by employing Bader＇s atoms in molecules theory （AIM）.

Density Functional Study on the Vibrational Frequencies of Hydrazoic Acid and Methyl Azide

Harmonic vibrational frequencies of hydrazoic acid and methyl azide are calculated using HF. MP2 methods and five popular density functional (DFT) methods and compared with experimental results. Of these seven methods, BLYP reproduces the observed frequencies most satisfactorily, while the results in HF and MP2 are worse. These indicate the BLYP calculation is a very promising approach for understanding the observed spectral features.

Theory Study on Structures and Vibrational Frequencies of Pyruvic acid

Density functional theory BLYP (using Becke's and Lee-Yang-Pars's correlation functionals), ab initio Hartree-Fock (HF) and hybrid DFT/HF B3LYP calculations were carried out to study the structure and vibrational spectra of pyruvic acid. The scaled B3LYP/6-31G* frequencies correspond well with available experimental assignment of the functional vibrational modes and the mean absolut devation is only 12.3cm^(-1).

First-principles studies of the vibrational properties of amorphous carbon nitrides

Raman spectra of amorphous carbon nitride films （a-C：N） resemble those of typical amorphous carbon （a-C）, and no specific features in the spectra are shown due to N doping. The present work provides a correlation between the microstructure and vibrational properties of a-C：N films from first principles. The six periodic model structures of 64 atoms with various mass densities and nitrogen contents are generated by the liquid-quench method using Car-Parinello molecular dynamics. By using Raman coupling tensors calculated with the finite electric field method, Raman spectra are obtained. The calculated results show that the vibrations of C=N could directly contribute to the Raman spectrum. The similarity of the Raman line shapes of N-doped and N-free amorphous carbons is due to the overlapping of C=N and C=C vibration bands. In addition, the origin of characteristic Raman peaks is also given.

Influence of ligand architecture on the structure of coordination centre in dimeric europium carboxylates with 1,10-phenanthroline

Methods of optical spectroscopy and X-ray crystallography data were used to examine the effect of architecture of carboxylate anions on structure of the Eu3＋ coordination centre in europium earboxylates with 1,10-phenanthroline Eu（RCOO）3·Phen. Luminescence spectra of europium acetate, nitropropionate, benzoate, naphthylcarboxylates, phenylacetates, phenoxyacetate, triphenylpropionate were investigated. A few of europium carboxylates with 2,2＇-bipyridine Eu（RCOO）3·Bpy and europium salts Eu（RCOO）3·nH2O were also studied. Vibrational IR and Raman spectra of phenylacetate family were analyzed. The crystal structure of nitropropionate Eu（NO2C2H4COO）3·Phen was solved by X-my diffraction method. The predominant influence of steric hindrances on Eu^3＋ coordination centre was observed at increase of the size of aromatic flagment of carboxylate anions. It was demonstrated, that introduction of the methylene bridges between the carboxylic group and aromatic rings of ligand weakens the effect of steric factor.

FT-Raman Spectroscopic Studies on the Interaction of Metal Ions With Sphingomyelin Bilayer

The interaction of trivalent lanthanide ions and divalent calcium ions with sph-'ngomyelm bilayer has been studied by FT-Raman spectroscopy.The results showed that the bonding of metal ions to the phosphate group of sphingomyelin bi-iayer,either La3+or Ca2+did not change the conformation of the choline group,that is,O-C-C-N+is still in its gauche conformation.The presence of metal ions changed the states of the interfacial region from liquid-like to amorphous state and even to crystalline.They increased the fluidity of acyl chains of sphingomyelin bilaver and made them packed disorderly.

Infrared Spectroscopic and Theoretical Studies on Cobalt(Ⅱ) Complex of Maleinitriledithiolate and 4, 4′-Dimethyl-2, 2′-bipyridine

The complete experimental IR spectra and vibrational analysis of the title complex Co(mnt)(dmbpy) were reported in this paper. The results show that the complex molecule has a planar geometry belonging to point group C 2v and ground electronic state with spin quartet. A new method for analyzing vibrational spectra of complicated molecule is established. The essential of this method is to point out main fixed points and pivotal vibrational units in assignment for each fundamental band. Two new symbols η (heaving along the specified direction) and M (midpoint of a bond or unit) were defined for describing the vibrational modes accurately.

Theoretical insights into photochemical ESITP process for novel DMP-HBT-py compound

We execute the density functional theory(DFT) and time-dependent density functional theory(TDDFT) approaches to make a detailed exploration about excited state luminescent properties as well as excited state intramolecular proton transfer(ESIPT) mechanism for the novel 2,6-dimethyl phenyl(DMP-HBT-py) system. Firstly, we check and confirm the formation and stabilization of hydrogen bonding interaction for DMP-HBT-py. Via optimized geometrical parameters of primary chemical bond and infrared(IR) spectra, we find O–H··· N hydrogen bond of DMP-HBT-py should be strengthened in S1 state. Insights into frontier molecular orbitals(MOs) analyses, we infer charge redistribution and charge transfer(ICT)phenomena motivate ESIPT trend. Via probing into potential energy curves(PECs) in related electronic states, we come up with the ultrafast ESIPT behavior due to low potential barrier. Furthermore, we search the reaction transition state(TS)structure, the ultrafast ESIPT behavior and mechanism of DMP-HBT-py compound can be re-confirmed. We sincerely wish this work could play roles in further developing novel applications based on DMP-HBT-py compound and in promoting efficient solid emitters in OLEDs in future.