Vibrational Assignment Of Fundamental Modes Research Articles

Ab initio and density functional computations of the vibrational spectrum, molecular geometry and some molecular properties of the antidepressant drug sertraline (Zoloft) hydrochloride

Sertraline hydrochloride is a highly potent and selective inhibitor of serotonin (5HT). It is a basic compound of pharmaceutical application for antidepressant treatment (brand name: Zoloft). Ab initio and density functional computations of the vibrational (IR) spectrum, the molecular geometry, the atomic charges and polarizabilities were carried out. The infrared spectrum of sertraline is recorded in the solid state. The observed IR wave numbers were analysed in light of the computed vibrational spectrum. On the basis of the comparison between calculated and experimental results and the comparison with related molecules, assignments of fundamental vibrational modes are examined. The X-ray geometry and experimental frequencies are compared with the results of our theoretical calculations.

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).

Density functional theory study of vibrational spectra of acridine and phenazine

Density functional theory (DFT) calculations using Becke's exchange in conjunction with Lee–Yang–Parr's correlation functionals (BLYP), Becke's three-parameter hybrid DFT/HF method using Lee–Yang–Parr's correlation functionals (B3LYP) and ab initio Hartree–Fock (HF) method have been carried out to investigate the structure and vibrational spectra of acridine and phenazine. Structural parameters obtained by B3LYP/6-31G* geometry optimization are in good agreement with available experimental data. The raw BLYP non-CH stretching frequencies approximate the experimental results much better than the HF results with the mean absolute deviation about 16 cm −1. The scaled B3LYP frequencies are more reliable than that of the BLYP and HF methods with the mean absolute deviation about 17 cm −1. On the basis of the comparison between calculated and experimental results, assignments of fundamental vibrational modes are examined. Also the structure and vibrational frequencies are compared with those of anthracene, pyridine and benzene to study the similarities and differences.

Structures and vibrational frequencies of pyruvic acid: density functional theory study

Density functional theory BLYP (using Becke's exchange and Lee–Yang–Parr'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. Molecular conformation calculations were made for two possible conformers (eclipsed and staggered of C4O8 bond with respect to the methyl group) of the compound. Calculated results show that the stable conformer of pyruvic acid is the eclipsed one. The raw BLYP and B3LYP frequencies approximate the experimental results much better than the Hartree–Fock results, the scaled B3LYP results are more reliable than that of the BLYP and HF methods with the mean absolute deviation about 12.3 cm −1. On the basis of the comparison between calculated and experimental results, assignments of fundamental vibrational modes are examined.

Vibrational frequencies of hydrazoic acid and methyl azide: density functional theory study

AbstractHarmonic vibrational frequencies of HN3 and CH3N3 molecules and their several isotopomers are calculated using HF, MP2 and five popular density functional theory (DFT) methods. On the basis of the comparison between calculated and experimental results, assignments of fundamental vibrational modes are examined. HF and MP2 results are in bad agreement with experimental values. Of the five DFT methods, BLYP reproduces the observed fundamental frequencies the most satisfactorily. Two hybrid DFT methods are found to yield frequencies generally higher than the observed fundamental frequencies. The results indicate that BLYP calculation is a very promising approach for understanding the observed spectral features.

Vibrational spectra of cyclic phosphazenes

The vibrational spectra of three cyclic phosphazene molecules, [N3P3Cl4(O2C12H8)] (CP1), [N3P3Cl2(O2C12H8)2] (CP2) and [N3P3(O2C12H8)3] (CP3), are reported. The far-infrared, infrared and Raman spectra were recorded. The assignment of fundamental vibrational modes is assisted by quantum chemical computations of wavenumbers and Raman and infrared intensities. Fundamental vibrational modes characterized by wavenumber and intensity are identified in the infrared and Raman spectra of the series. Copyright © 1999 John Wiley & Sons, Ltd.

On the Aqueous Vibrational Spectra of Alkali Metal Oxalates

Fourier transform infrared attenuated total reflectance and Fourier transform Raman spectra of the series of aqueous alkali metal oxalates—lithium oxalate (Li2C2O4), sodium oxalate (Na2C2O4), potassium oxalate (K2C2O4), rubidium oxalate (Rb2C2O4), and cesium oxalate (Cs2C2O4)—are presented for the first time. Fourier transform Raman spectra of the solid oxalates are also presented for the first time. The solid and aqueous oxalate ions are assumed to possess D2 h and D2 d symmetry, respectively, and the assignment of fundamental vibrational modes is made accordingly. The effect of increasing alkali metal ion concentration on the aqueous spectra of these oxalates is also reported. Spectral changes are explained in terms of the ability of the respective alkali metal cations to interact with the oxalate anion in solution. It is proposed that these differences arise because the alkali metal cations associate with the aqueous oxalate anions to varying degrees, depending upon the nature of the cation. The extent of the binding is found to decrease down the alkali metal series (Li > Na > K > Rb > Cs). Similar results obtained for the tetramethylammonium cation [(CH3)4N+] suggest that it is a softer cation than cesium.

Density functional theory study of vibrational spectra. 3. Assignment of fundamental vibrational modes of quadricyclane

Density functional theory BLYP (Becke's exchange and Lee-Yang-Parr'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 quadricyclane. The BLYP/6-31G * and scaled HF/6-31G * frequencies correspond well with each other and with available experimental assignment of the fundamental vibrational modes. Based on conformity between the calculated and experimental results, a plausible assignment of two remaining a 1 modes and all non-CH stretching a 2, b 1, and b 2 modes is proposed.

On assignment of fundamental vibrational modes of hypophosphite anion and its deuterated analogue

Results of ab initio and density functional theory calculations on the structure and vibrational frequencies of hypophosphite anion indicate earlier experimental assignments of the fundamental vibrational modes are correct while the recent reassignments of several modes proposed by Bickley et al. are inconsistent with the calculated results.

Vibrational spectra of bexabromobenzene and hexaiodobenzene

Infrared and Raman spectra of polycrystalline C 6Br 6 and C 6I 6 are measured at both room temperature and liquid nitrogen temperatures. Vibrational assignment of fundamental modes as well as combination bands are established on the basis of normal coordinate analysis.

Raman spectra and vibrational assignments of hexacyano-complexes

The Raman spectra of the potassium salts of [M(CN)6]3–(M = Co, Fe, Mn, and Cr) and [M(CN)6]4–(M = Fe and Ru), have been measured in the solid state and in aqueous solution and also of solid K4[Mn(CN)]6, 3H2O and K5[Mn(CN)6],H2O. The i.r. spectra of solid K5[Mn(CN)6],H2O, K4[V(CN)6],3H2O, and ‘K3[V(CN)6],H2O’ are also reported. Assignments of fundamental vibrational modes are proposed for the anions on the basis of these measurements and of published i.r. data, and the results are correlated with σ- and π-effects in the metal–cyanide bond.