Seda Sagdinc

Spectroscopic and DFT studies of flurbiprofen as dimer and its Cu(II) and Hg(II) complexes

The vibrational study in the solid state of flurbiprofen and its Cu(II) and Hg(II) complexes was performed by IR and Raman spectroscopy. The changes observed between the IR and Raman spectra of the ligand and of the complexes allowed us to establish the coordination mode of the metal in both complexes. The comparative vibrational analysis of the free ligand and its complexes gave evidence that flurbiprofen binds metal (II) through the carboxylate oxygen. The fully optimized equilibrium structure of flurbiprofen and its metal complexes was obtained by density functional B3LYP method by using LanL2DZ and 6-31 G(d,p) basis sets. The harmonic vibrational frequencies, infrared intensities and Raman scattering activities of flurbiprofen were calculated by density functional B3LYP methods by using 6-31G(d,p) basis set. The scaled theoretical wavenumbers showed very good agreement with the experimental values. The electronic properties of the free molecule and its complexes were also performed at B3LYP/6-31G(d,p) level of theory. Detailed interpretations of the infrared and Raman spectra of flurbiprofen are reported. The UV-vis spectra of flurbiprofen and its metal complexes were also investigated in organic solvents.

Theoretical and vibrational studies of 4,5-diphenyl-2-2 oxazole propionic acid (oxaprozin).

The molecular structure, linear and nonlinear optical properties, and electronic properties of 4,5-diphenyl-2-2 oxazole propionic acid (oxaprozin) as a monomer were investigated by using Hartree-Fock (HF) and density functional theory (DFT) calculations that used 6-31G(d,p) basis set. The first-order hyperpolarizability of oxaprozin (OXA) was found to be 1.117 x 10(-30) esu. The structure of oxaprozin dimer with HF/6-31G(d) level caused by the shifts of O-H and CO bands in the vibrational spectra of oxaprozin were also studied. Moreover, these calculated frequencies of oxaprozin dimer were compared with the solid FT-IR and FT-Raman spectra. The theoretical frequencies and infrared intensities were showed a good agreement with experimental data.

FT-IR and FT-Raman spectra, molecular structure and first-order molecular hyperpolarizabilities of a potential antihistaminic drug, cyproheptadine HCl.

Cyproheptadine hydrochloride (CYP HCl) {4-(5H-dibenzo[a,d]-cyclohepten-5-ylidene)-1-methylpiperidine hydrochloride} is a first-generation antihistamine with additional anticholinergic, antiserotonergic, and local-anesthetic properties. The geometry optimization, Mulliken atomic charges and wavenumber and intensity of the vibrational bands of all of the possible modes of CYP HCl have been calculated using ab initio Hartree-Fock (HF) and density functional theory (DFT) employing the B3LYP functional with the 6-311G(d,p) basis set. We have compared the calculated IR and Raman wavenumbers with experimental data. Quantum-chemical calculations of the geometrical structure, energies, and molecular electrostatic potential and NBO analysis of CYP HCl have been performed using the B3LYP/6-311G(d,p) method. The electric dipole moment (μ), static polarizability (α) and the first hyperpolarizability (β) values of the title compound have been computed using HF and DFT methods. The study reveals that the antihistaminic pharmacological property of CYP HCl has a large β value and, hence, may in general have potential applications in the development of non-linear optical materials. The experimental and calculated results for CYP HCl have also been compared with those for mianserin HCl.

Study of the solvent effects on the molecular structure and CO stretching vibrations of flurbiprofen.

The effects of 15 solvents on the C=O stretching vibrational frequency of flurbiprofen (FBF) were determined to investigate solvent-solute interactions. Solvent effects on the geometry and C=O stretching vibrational frequency, ν(C=O), of FBF were studied theoretically at the DFT/B3LYP and HF level in combination with the polarizable continuum model and experimentally using attenuated total reflection infrared spectroscopy (ATR-IR). The calculated C=O stretching frequencies in the liquid phase are in agreement with experimental values. Moreover, the wavenumbers of ν(C=O) of FBF in different solvents have been obtained and correlated with the Kirkwood-Bauer-Magat equation (KBM), the solvent acceptor numbers (ANs), and the linear solvation energy relationships (LSERs). The solvent-induced stretching vibrational frequency shifts displayed a better correlation with the LSERs than with the ANs and KBM.

Experimental and theoretical evaluation of the inhibition properties of ketoprofen for the corrosion of a copper surface in hydrochloric acid

Ketoprofen (KETO) was studied as a corrosion inhibitor for copper in 0.5 M HCl solution using experimental (potentiodynamic polarization curves) and quantum chemical methods. The results obtained from the experiments demonstrated that inhibition efficiency increases with an increase in the concentration of KETO. Additionally, the results of potentiodynamic polarization curves demonstrated that KETO is a mixed-type inhibitor. The adsorption of KETO on a copper surface followed a Langmuir adsorption isotherm. The adsorption equilibrium constant and adsorption free energy were calculated from a Langmuir adsorption isotherm. Density functional theory (DFT) was used for theoretical calculations. The corrosion inhibition efficiencies of non-protonated (neutral) and protonated forms of KETO were determined in both the gas and aqueous phases. The calculated parameters for the various protonated and non-protonated KETO forms were compared with one another.

Molecular structures, spectroscopic (FT–IR, NMR, UV) studies, NBO analysis and NLO properties for tautomeric forms of 1,3-dimethyl-5-(phenylazo)-6-aminouracil by density functional method

The equilibrium geometry, nuclear magnetic resonance (NMR) and UV-Vis analysis, and vibrational frequencies for the azo and hydrazone isomers of 1,3-dimethyl-5-(phenylazo)-6-aminouracil have been performed using density functional theory (DFT/B3LYP) method with 6-311G(d,p) basis set. A detailed interpretation of the vibrational spectra has been made on the basis of the calculated potential energy distribution (PED) obtained from the Vibrational Energy Distribution Analysis (VEDA4) program. The 1H NMR chemical shifts with respect to TMS were calculated by the gauge independent atomic orbital (GIAO) method and compared with the experimental data. Stability of the molecule arising from hyper conjugative interactions, charge delocalization has been analyzed using natural bond orbital (NBO) analysis. Using the TD-DFT method, electronic absorption spectra in CHCl3 solvent of the title compound have been predicted, and good agreement is determined with the experimental one. The NLO properties such as mean polarizability (⟨α⟩), the anisotropy of the polarizability (⟨Δα⟩) and the mean first-order hyperpolarizability (⟨β⟩) were computed by using finite field method. The computed values of μ, α and β for the azo and hydrazone forms of the title molecule are 5.4717 and 3.8905 D, 2.7773×10-23 and 2.7598×10-23esu, and 3.4499×10-30 and 6.8504×10-30esu, respectively. The high β values and non-zero values of μ indicate that the title compound might be a good candidate for NLO material.

Density functional theory studies on the corrosion inhibition of benzoin, benzil, benzoin-(4-phenylthiosemicarbazone) and benzil-(4-phenylthiosemicarbazone) of mild steel in hydrochloric acid

The density functional theory (DFT) calculations were performed on benzoin (BN), benzil (BL), benzoin-(4-phenylthiosemicarbazone) (BN4PTSC) and benzil-(4-phenylthiosemicarbazone) (BL4PTSC) used as corrosion inhibitors for mild steel in acidic medium. The quantum chemical parameters/descriptors, namely, EHOMO (highest occupied molecular orbital energy), ELUMO (lowest unoccupied molecular orbital energy), the energy difference (ΔE) between EHOMO and ELUMO, dipole moment (μD), electron affinity (A), ionization potential (I), the absolute electronegativity (χ), absolute hardness (η), softness (σ), polarizability (α), the Mulliken charges, and the fraction of electrons (ΔN) transfer from inhibitors to iron, were calculated and correlated with the experimental IE%. Condensed Fukui functions have been used to determine the sites for electrophilic and nucleophilic attacks on each of the inhibitors.

Theoretical elucidation on corrosion inhibition efficiency of 11-cyano undecanoic acid phenylamide derivatives: DFT study

The inhibition effects of 11-cyano undecanoic acid phenylamide derivatives against corrosion are studied by means of density functional approach B3LYP/6-311G(d,p) calculations. The efficiencies of corrosion inhibitors and the molecular structure relate to some parameters, such as EHOMO, ELUMO, the energy gap between ELUMO and EHOMO (ΔE = ELUMO − EHOMO), dipole moments (μ), and other parameters, including electronegativity (χ), global hardness (η), softness (ρ), chemical potential (μc) and the fraction of electrons transferred from the inhibitor molecule to metallic atom (ΔN). The computed quantum chemical properties indicate good correlation with experimental corrosion inhibition efficiencies of 11-cyano undecanoic acid phenylamide derivatives. A good correlation between the substituent type and inhibition efficiency of inhibitors through the application of Hammett relationship is obtained. The linear correlation is also found between the Hammett parameters and calculated molecular orbital energies.

Molecular structure, FT-IR, FT-Raman, NMR studies and first order molecular hyperpolarizabilities by the DFT method of mirtazapine and its comparison with mianserin

Mirtazapine (±)-1,2,3,4,10,14b-hexahydro-2-methylpyrazino(2,1-a)pyrido(2,3-c)(2)benzazepine is a compound with antidepressant therapeutic effects. It is the 6-aza derivative of the tetracyclic antidepressant mianserin (±)-2-methyl-1,2,3,4,10,14b-hexahydrodibenzo[c,f]pyrazino[1,2-a]azepine. The FT-IR and FT-Raman spectra of mirtazapine have been recorded in 4000-400 cm(-1) and 3500-10 cm(-1), respectively. The optimized geometry, energies, nonlinear optical properties, vibrational frequencies, (13)C, (1)H and (15)N NMR chemical shift values of mirtazapine have been determined using the density functional theory (DFT/B3LYP) method. A comparison of the experimental and theoretical results of mirtazapine indicates that the density-functional B3LYP method is able to provide satisfactory results for predicting vibrational and NMR properties. The experimental and calculated results for mirtazapine have also been compared with mianserin.

Theoretical study on the relationship between the molecular structure and corrosion inhibition efficiency of long alkyl side chain acetamide and isoxazolidine derivatives

Quantum mechanics calculations have been applied to three long alkyl side chain acetamides and three isoxazolidine derivatives used as corrosion inhibitors. The corresponding structures have been optimized, and the highest occupied molecular orbital energy (EHOMO), the lowest unoccupied molecular orbital energy (ELUMO), energy gap (ΔE), electronegativity (χ), hardness (η), softness (σ) and the fraction of electrons transferred from the inhibitor molecule to the metal surface (ΔN) have been calculated using the DFT/B3LYP and HF methods with the 6–31G(d, p) basis set. The electric dipole moment (μ), the mean polarizability (〈α〉) and the first order hyperpolarizability (β) values of the investigated molecules have been computed using the same methods. The calculation results also show that the molecules might have microscopic nonlinear optical (NLO) behaviour with non-zero values. Finally, the theoretical results obtained have been compared with the experimental data.