Effect of Long-Range Corrections on Intermolecular Interactions and Vibrational Assignments of Ethylene Oxide Dimer. A Combined DFT and SQFF Study

Theoretical structural and vibrational study for the ethylene oxide dimer have been performed by using the experimental structure determined by X-ray diffraction, the vibrational spectra and, the functional hybrids B3LYP/6-311++G** and WB97XD/6-311++G** methods. Here, the effects of dispersion on intermolecular interactions and on complete assignments of infrared and Raman spectra of dimer have been performed combining the Pulay´s scaled quantum mechanical force field (SQMFF) methodology with those two levels of calculations in order to fit the theoretical wavenumbers values to the experimental ones. Calculations including long-range corrections have revealed similar optimized energy, volume and frequencies to calculated with the B3LYP/6-31G* method, lower correlations in the geometrical parameters, higher stabilization energy, higher values in the topological parameters and higher scaled force constants than the obtained at B3LYP/6-311++G** level. Natural bond order (NBO) and atoms in molecules theory (AIM) studies with both methods reveal two types of intermolecular interactions (C-O···H and C-O···O) in the ethylene oxide dimer in accordance with the bands observed in the experimental Raman spectrum at low temperatures and with the experimental structure determined at 100 K. The nature of those interactions and their topological properties were studied by using NBO and AIM calculations. The studied properties for the ethylene oxide dimer were analyzed and compared with those obtained for the monomer. Similar assignments of the vibrational modes for dimer were obtained using the three different methods

A combined study on structures and vibrational spectra of the antiviral rimantadine using SQMFF and DFT calculations

In this research, a combined study on structures and vibrational spectra of antiviral rimantadine have been performed using hybrid B3LYP/6-311 thorn thorn G** calculations and the scaled quantum force field (SQMFF) proced-ure. Harmonic force fields and scaled force constants of Free Base (FB), Cationic (CA) and Hydrochloride (HCl) species derived from the antiviral rimantadine have been calculated in gas phase and in aqueous solution using normal internal coordinates and scaling factors. Good correlations were acquired comparing the theoretical IR, Raman, 1H- 13C-NMR and UV spectra of three species with the analogous experimental ones, suggesting probably, the presence of all them in both phases. The main force constants of three species have evidenced lower values than the corresponding to antiviral amantadine. The ionic character of N1-H33 center dot center dot center dot Cl36 bond of HCl species in aqueous solution evidence positive Mulliken charge on N1 atom indicating that this species is as CA one. Rimantadine presents higher solvation energies in water than other antiviral species, such as chloroquin, niclo-samide, cidofovir and brincidofovir. The FB and HCl species of rimantadine are slightly less reactive than the corresponding to amantadine while the opposite is observed for the CA species. The predicted ECD spectra for the FB and CA species show positive Cotton effect different from the negative observed for the HCl one. These different behaviours of three species of rimantadine could probably explain the differences observed in the in-tensities of bands predicted in the electronic spectra of these species.Peer reviewe

Structural and Vibrational Properties and NMR Characterization of (2’-furyl)-Imidazole Compounds

The furylimidazoles compounds have a great importance in biochemistry and pharmacology because many of them present interesting properties. They are also found in artificial compounds, such as agrochemicals, pharmaceuticals, dyes, plastics, solvents, photographic chemicals, electronics, corrosion inhibitors, preservatives, and polymers. They can be used in synthetic organic chemistry as building blocks, due to their presence as key structural units in many natural products and in important pharmaceuticals. For example, the nature of the N- atoms in the imidazole molecule makes possible an extraordinary variety of reactions and this is the main reason for the great biological importance of the amino acid, histidine.Fil: Ledesma, Ana Estela. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Tucumán. Instituto de Química del Noroeste. Grupo Vinculado Unse-inquinoa; ArgentinaFil: Zinczuk, Juan. Universidad Nacional de Rosario. Facultad de Ciencias Bioquímicas y Farmacéuticas; ArgentinaFil: López González, Juan J.. Universidad de Jaén; EspañaFil: Brandan, Silvia Antonia. Universidad Nacional de Tucumán. Facultad de Bioquímica, Química y Farmacia. Instituto de Química Inorgánica. Cátedra de Química General.; Argentin

A crystallographic and vibrational study of cesium di-μ-aqua bis[tetraaquasodium(I)] decavanadate, Cs₄[Na₂(H₂O)₁₀](V₁₀O₂₈)

The title compound crystallizes in the triclinic space group P͞1, with a = 8.6161(4) Å, b = 10.591(1) Å, c = 11.406(1) Å, α = 67.976(7)°, β = 86.868(6)°, γ = 67.798(6)°, and Z = 1. The structure was refined to R1 = 0.0413. The decavanadate anion V₁₀O₂₈⁶⁻ and the [Na₂(H₂O)₁₀]²⁺ bridged cation are located at inversion centers. Partial deuteration of the substance indicates that the coordinated water molecules are strongly asymmetric, forming weak hydrogen bonds with acceptor oxygen atoms from the decavanadate anion. The infrared and Raman spectra are dominated by the water and decavanadate anion bands.Instituto de Física La PlataCentro de Química Inorgánic

Impact of Different Groups on Properties of All Members of the Series of 1-X-Benzotriazole Derivatives (X= H, OH, NH2, Cl and CH3)

Here, the impact of different groups on the geometrical parameters, dipole moments, atomic charges, stabilization and solvation energies, molecular electrostatic potentials, densities rings, positions IR and UV bands and NMR chemical shifts of all members of the series of 1X-benzotriazole derivatives (X= H, CH3, Cl, NH2 and OH) have been investigated by using hybrid B3LYP/6-311++G** calculations because, so far, correlations among their properties neither the vibrational analyses are reported yet. The polarity of N-X bonds, electronegativity, donor/acceptor characteristics of the different X groups were analysed for all members. The polarity of N1-X4 bonds have influence on dipole moments, volumes and on bond lengths of both rings while the chlorinated derivative has a higher reactivity due to its higher global electrophilicity index. NBO and AIM studies reveal the strong influence of Cl on densities of both rings of CBT and, on this derivative. Harmonic force fields evidence very good correlations between stretching force constants and assignments

Theoretical Investigation on Monomer and Dimers of Inhibitor of Cytochrome P450 Enzymes: 1-Aminobenzotriazole

In this research, structures and properties of monomer and two dimers (1 and 2) of inhibitor of cytochrome P450 enzymes, 1-Aminobenzotriazole (ABT) have been studied by using functional hybrid B3LYP/6-311++G** calculations. The very good correlations observed between theoretical and experimental 1H-, 13C-NMR, FT-IR and FT-Raman spectra suggest that C-H···N interactions of dimeric species should be expected in the solid phase, as was observed in the experimental crystalline structure of a quinolin benzotriazole derivative. NBO and AIM calculations suggest that dimer 2 with inverted positions of its monomers could be present in the solid phase because it evidence higher stabilities in both media. On the other hand, frontier orbitals studies support a higher reactivity of dimer 2 of ABT higher than the monomer and dimer 1, for which, the presence of dimer 2 containing N-NH2 groups in ABT could justify the biological activities observed for this species with gap values between 4.5933 and 4.8164 eV different from antiviral agents containing the C-NH2 moiety, as amantadine and chloroquine whose gap values are around 4.3012-4.1116 eV. Finally, the presence of bands of monomer and of both dimers are predicted in the vibrational spectra and, hence, its completes assignments have been performed. The scaled force constants for the three studied species are also reported

Vibrational Characterization of Active Drug to the Treatment of Chagas Disease, Benznidazole by Using Force Fields and Internal Coordinates

Two experimental structures of benznidazole active drug used to the treatment of Chagas disease have been structurally characterized and its vibrational spectra completely assigned combining B3LYP/6-311++G** calculations with the experimental FT-IR and FT-Raman spectra and the SQMFF methodology. The most stable conformer of benznidazole found in the study of the potential energy surface is in agreement with that experimentally observed by X-ray diffraction at room temperature while the other one was observed with the heating up to 195 ºC. Both differs in the positions of CH2 groups of acetamide fragment. Their structural properties in gas phase and ethanol solution were computed by using natural bond orbital (NBO), atoms in molecules (AIM), Merz-Kollman (MK) charges, molecular electrostatic potentials (MEP) and frontier orbitals calculations by using the hybrid B3LYP method and the 6-31G* and 6-311++G** basis sets. Additional WB97XD/6-311++G** calculations show that the energy values optimized for the most stable species in both media present lower values than the obtained with the B3LYP/6-31G* method. The vibrational assignments for those two conformers in both media were obtained from their corresponding harmonic force fields together with the scaled force constants

A crystallographic and vibrational study of cesium di-μ-aqua bis[tetraaquasodium(I)] decavanadate, Cs₄[Na₂(H₂O)₁₀](V₁₀O₂₈)

The title compound crystallizes in the triclinic space group P͞1, with a = 8.6161(4) Å, b = 10.591(1) Å, c = 11.406(1) Å, α = 67.976(7)°, β = 86.868(6)°, γ = 67.798(6)°, and Z = 1. The structure was refined to R1 = 0.0413. The decavanadate anion V₁₀O₂₈⁶⁻ and the [Na₂(H₂O)₁₀]²⁺ bridged cation are located at inversion centers. Partial deuteration of the substance indicates that the coordinated water molecules are strongly asymmetric, forming weak hydrogen bonds with acceptor oxygen atoms from the decavanadate anion. The infrared and Raman spectra are dominated by the water and decavanadate anion bands.Instituto de Física La PlataCentro de Química Inorgánic

Impact of non-covalent interactions on FT-IR spectrum and properties of 4-methylbenzylammonium nitrate : a DFT and molecular docking study

In this research, the impact of non-covalent interactions on the FT-IR spectrum and structural, electronic, topological and vibrational properties of hybrid 4-methylbenzylammonium nitrate (4MBN) have been studied combining B3LYP/CC-PVTZ calculations with molecular docking. 4MBN was synthesized and characterized by using the FT-IR spectrum while the optimized structures in gas phase and in ethanol and aqueous solutions have evidenced monodentate coordination between the nitrate and methylbenzylammonium groups, in agreement with that experimental determined for this species by X-ray diffraction. Here, non-covalent interactions were deeply analyzed in terms of topological parameters (AIM), electron localization function (ELF), localized orbital locator (LOL), Hirshfeld surface and reduced density gradient (RDG) method. Weak interactions such as H-bonds, VDW and steric effect in 4MBN were visualized and quantified by the independent gradient density (IGM) based on the promolecular density. The hyper-conjugative and the delocalization of charge in 4MBN have been elucidated by natural bonding orbital (NBO) while its chemical reactivity was studied and discussed by using molecular electrostatic potential surface (MESP), frontier molecular orbital (FMOs), density of state (DOS) and partial density of state (PDOS). The complete vibrational assignments of 69 vibration modes expected for 4MBN are reported together with the scaled force constants while the electronic transitions were evaluated by TD-DFT calculations in ethanol solution. Thermal analysis (DTA and DSC) was also determined. Molecular docking calculations have suggested that 4MBN presents biological activity and could act as a good inhibitor against schizophrenia disease