Study Of Substitution Effects Research Articles

On the search of cumulative effect of fluoro-substituents in the structural and vibrational properties of sulfinylanilines: Study of 3,4-difluorosulfinylaniline and 2,3,4-trifluorosulfinylaniline

The study of substitution effects on the structural and vibrational properties of a series of recently reported mono fluoro-substituted sulfinylanilines proceeds a step forward with the present study of 3,4-difluorosulfinylaniline and 2,3,4-trifluorosulfinylaniline. These substances were synthesized and characterized by FTIR, Raman and NMR spectra, which were subsequently compared with theoretical spectra, obtained by quantum chemical calculations at different levels of theory. The number of signals in the vibrational spectra, together with the analysis of the potential energy surface of both compounds reveal the presence of stable conformers possessing the angular NS→O group in a syn conformation of the CN and S→O bonds and coplanar with the ring plane. According to the Natural Bond Orbital analysis performed, the prevalence of a given structure of the stable syn conformer over other local minima of the potential energy surface obtained upon rotation around the NS and CN bonds is a consequence of different orbital interactions. The planar conformation predicted for stable minima are stabilized by conjugation between the π-systems of the NS→O group and the ring and by a weak orbital interaction between oxygen and the ortho hydrogen closest to it.

On the search of the influence of substituents in the structural and vibrational properties of p-substituted sulfinylanilines: Study of p-trifluoromethylsulfinylaniline

The study of substitution effects on the structural and vibrational properties of para substituted sulfinylanilines proceeds a step forward with the study of p-trifluoromethylsulfinylaniline, synthesized and characterized by NMR, Raman, FTIR and mass spectra. The experimental spectra were compared and analyzed taking into account theoretical spectra obtained with quantum chemical calculations at different levels of theory. The spectroscopic results reveal the presence of a single form of this molecule which, according to the calculated molecular structure, possesses the NSO group coplanar with the ring plane. In addition, the syn conformation of the NSO group is also derived from both, experimental and theoretical data. The presence of the CF3 group in the para position of the aromatic ring influences the properties of the NSO group, with the NS bond more strongly affected than the SO bond compared to results reported for other para substituted sulfinylanilines.

Sol–gel synthesis, characterization and study of substitution effects in different gallium-containing garnets

Gallium-containing garnets (gadolinium gallium Gd3Ga5O12; GGG, and gadolinium scandium gallium Gd3Sc2Ga3O12; GSGG) were prepared using an aqueous sol–gel synthesis route. Different starting materials and TRIS (tris-(hydroxymethyl)-aminomethane), NH2C(CH2OH)3 and 1,2-ethandiol as complexing agents were used in the sol–gel processing. The final products were obtained after the heating of the precursor gels at 1000 °C for 10 h. The substitution effects of Fe3+, Ce3+, and Ce3+/Cr3+ in gallium garnets have been also investigated. The results obtained in this study have demonstrated that the formation of mixed-metal gallium garnets depends on the sol–gel synthesis parameters and nature of dopant element. The luminescent properties of GGG:Fe3+ specimens were identical to those of GSGG:Fe3+, showing the great iron quenching effect. The luminescence at 720–780 nm for the cerium-/chromium-co-doped GGG:Ce3+, Cr3+ phosphors was observed. The highest emission intensity for GGG:Ce3+, Cr3+ samples containing 3 mol% of dopants (1.5 mol% Ce and 1.5 mol% Cr) was determined. Cerium/chromium concentration-dependent luminescence spectra of doped GGG:Ce3+, Cr3+ samples. PL excitation spectrum (λ em = 730 nm) of pure GGG is presented at left. Emission spectra (λ ex = 460 nm) of GGG:Ce3+, Cr3+ as a function of Ce3+ and Cr3+ concentration are presented at right.

A theoretical study of substitution effects on halogen–π interactions

Ab initio calculations are performed to analyse the existence of intermolecular halogen···π interactions in NCX complexes with YC≡CY, where X = Cl, Br and Y = H, CN, F, Cl, OH, NH2, and CH3. Molecular geometries and interaction energies of the complexes are investigated at the MP2/aug-cc-pVTZ level of theory. Our results indicate that the interaction energies for the NCX···YC≡CY complexes lie in the range between −0.5 and −5.9 kcal/mol. The physical nature of the interactions is studied using symmetry-adapted perturbation theory (SAPT). The stability of the X···π interactions is predicted to be attributable mainly to electrostatic and dispersion effects.

Quantum chemical studies on para-substituted styrenyl fullerene. Study of substitution effects on structural and electronic properties

Quantum chemical investigations on para-substituted styrenyl fullerene derivatives with substituents linked to para position of styrenyl group have been carried out. The density functional theory (DFT) have been used in this study with B3LYP functional and the modest 3-21G* basis sets. The substituents were variable donating and withdrawing to study the effect of such structural change on the structural and electronic properties of the studied molecules.

Angle-resolved X-ray photoelectron spectroscopy (ARXPS) study of substitution effects in Sb 2Te 3 − xSe x. crystals and their influence on density of antisite defects

An angle-resolved X-ray photoelectron spectroscopy (ARXPS) method is first introduced for elucidation of the mechanism of Te substitution by Se in Sb 2Te 3 crystals. The obtained results are consistent with the substitution of the selenium atoms predominantly into the Te 2 atomic layers. The observed substitution makes it possible to evaluate the interactions of incorporated Se atoms with antisite defects, Sb′ Te. The incorporation of Se atoms into the lattice increases ionicity of crystal bonds and suppresses the Sb′ Te defect concentration, which is accompanied by a decrease in hole concentration.

13C NMR and IR study of substitution effects and mass spectra of biphenyl analogues of α-cyanochalcones

Thirteen biphenyl analogues of α-cyanochalcones IIa-IIm were prepared by condensation of p-phenylbenzoylacetonitrile (I) with p-substituted benzaldehydes. Their 13C NMR chemical shifts were measured and correlated with the Hammett parameters (σ, σ+) and the Swain-Lupton reactivity parameters. A consistent picture of the transmission of the substituent (electronic) effects through the carbon skeleton of the studied compounds was obtained. The relationship between the structure of synthetized α-cyanochalcones and their mass spectra is discussed.