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DFT calculations were used to access information about structure, energy and electronic properties of series of phenyl- and phenoxymethyl-(thio)semicarbazone derivatives with demonstrated activity against the larvae of Aedes aegypti in stage L4. The way as the thiosemicarbazone derivatives can interact with solvents like DMSO and water were analyzed from the comparison between calculated and experimental 1 H NMR chemical shifts. The evidences of thiosemicarbazone derivatives making H-bond interaction to solvent have provide us insights on how they can interact with a potential A . aegypti ’ s biological target, the Sterol Carrier Protein-2. [ABSTRACT FROM AUTHOR]

A set of aryl- and phenoxymethyl-(thio)semicarbazones were synthetized, characterized and biologically evaluated against the larvae of Aedes aegypti ( A. aegypti ), the vector responsible for diseases like Dengue and Yellow Fever. (Q)SAR studies were useful for predicting the activities of the compounds not included to create the QSAR model as well as to predict the features of a new compound with improved activity. Docking studies corroborated experimental evidence of AeSCP- 2 as a potential target able to explain the larvicidal properties of its compounds. The trend observed between the in silico Docking scores and the in vitro pLC50 (equals −log LC50, at molar concentration) data indicated that the highest larvicidal compounds, or the compounds with the highest values for pLC50, are usually those with the higher docking scores (i.e., greater in silico affinity for the AeSCP-2 target). Determination of cytotoxicity for these compounds in mammal cells demonstrated that the top larvicide compounds are non-toxic. [ABSTRACT FROM AUTHOR]

Usnic acid is a secondary metabolitefound in several species oflichens, organisms resulting from the symbiosis between fungi andalgae. This compound has been extensively studied because of its pharmacologicalproperties. Despite its potential medicinal importance, it exhibitsa high degree of toxicity. The confinement of the usnic acid withinliposomes has been investigated as a possibility to reduce its toxicity.In this work, we characterize the interaction of usnic acid in itsneutral and anionic states (usniate) with DPPC and DOPC by means ofmolecular dynamics simulations. A lamellar to nonlamellar transitionis observed for both membranes upon contact with usniate within 100ns time scale. The transition suggests the formation of a liposome-likestructure encapsulating the metabolyte. Furthermore, such processoccurs at a significantly shorter time frame for DOPC. [ABSTRACT FROM AUTHOR]

This research aimed to evaluate the effects of damages caused by Heilipodus naevulus Mann. (Coleoptera: Curculionidae) to the development of eucalyptus young plantation, and to record, for the first time, the occurrence on Espírito Santo State, Brazil. The critical period of occurrence was observed between October to December according with rain regime. The damages caused by the pest reduced the development and quality of eucalyptus trees. [ABSTRACT FROM AUTHOR]

The chemical compound hydantoin is commonly used in the synthesis of broad-spectrum medicaments with multiple pharmacological activities. There are several papers in literature describing hydantoin derivates, yet few are related to the isolated molecule. In this work, we have performed B3LYP and MP2 calculations with the 6-31++G(d,p) basis set in order to obtain the geometric, energetic, and electronic parameters of the isolated hydantoin and its dimers. We have performed a complete energetic analysis of these complexes considering corrections from the basis set superposition error ( BSSE) and zero-point energy (ZPE) approaches. On the basis of these results, we have proposed and tested an additive model which has successfully predicted the complexation energies of larges hydantoin complexes. © 2010 Wiley Periodicals, Inc. Int J Quantum Chem, 2010 [ABSTRACT FROM AUTHOR]

Abstract: B3LYP and MP2 theoretical calculations with 6-31++G(d,p) basis set have been performed to interpret the infrared spectrum of maleimide. The anharmonicity effect has been included to correct the calculated harmonic frequency values. As expected, this has allowed a better agreement with the experimental ones, especially B3LYP values. The more pronounced changes have been verified to the Xsp sp="0.25" />=C or N) stretching modes. The calculated IR intensities compare favorably well with their corresponding relative experimental values in vapor phase. The large discrepancy is found to the symmetric Cing mode of the heterocyclic ring. It appears to be a strong band at 897cm−1, in contrast to B3LYP and MP2 calculated values. The calculated intensities due to the out-of-plane and in-plane bending and stretching modes for the Xtors (X=C or N) have been adequately interpreted in terms of hydrogen atomic charges and Xfluxes extracted from the modified charge–charge flux-overlap model (CCFOM) for infrared intensities. [Copyright &y& Elsevier]

Abstract: MP2/6-31++G(d,p) and B3LYP/6-31++G(d,p) theoretical calculations have been employed to investigate the hydrogen bonding formation involving the vic-, cis- and trans-C2H2F2 isomers and hydrogen fluoride. Our calculations have revealed for each isomer the preferential existence of two possible hydrogen-bonded complexes: a non-cyclic complex and a cyclic complex. For all the three isomers the binding energies for the non-cyclic and cyclic hydrogen complexes are essentially equal using both the MP2 and B3LYP calculations, being that the cyclic structure is slightly more stable. For instance, the binding energies including BSSE and ZPE corrections for the non-cyclic and cyclic structures of cis-C2H2F···HF are 8.7 and 9.0kJmol−1, respectively, using B3LYP calculations. The cyclic complex formation reduces the polarity, in contrast to what occurs with the non-cyclic complex. This result is more accentuated in vic-C2H2F2···HF. In this latter, Δμ(cyclic) is −3.07D, whereas Δμ(non-cyclic) is +1.92D using B3LYP calculations. Their corresponding MP2 values are +0.44D and −1.89D, respectively. As expected, the complexation produces an Hing frequency downward shift, whereas its IR intensity is enhanced. On the other hand, the vibrational modes of the vic-, cis- and trans-C2H2F2 isomers are little affected by complexation. The new vibrational modes due to hydrogen bonding formation show several interesting features, in particular the HF bending modes which are pure rotations in the free molecule. [Copyright &y& Elsevier]

Abstract: B3LYP theoretical calculations with 6-31++G(d,p) basis set have been performed to study the infrared spectrum of maleimide and its dimer. Our calculations have shown that the dimer formation leads to a binding energy of 44.0kJmol−1 involving two intermolecular hydrogen bonds between the amide hydrogen and a carbonyl group of two neighboring maleimides. This value is essentially due to the electrostatic interaction term. Our calculations have also revealed the vibrational changes, in terms of frequencies and IR intensities, after dimer formation. The most affected modes are associated with the Ning and in-plane bending bands. This behavior can be adequately interpreted by the hydrogen atomic charge and Nflux based on the modified charge–charge flux-overlap model for infrared intensities. The B3LYP frequency shifts are in very good agreement with the experimental ones. [Copyright &y& Elsevier]

Abstract: MP2/6-31++G(d,p) ab initio molecular orbital calculations have been employed to investigate the effect of the F–H⋯N hydrogen bond between aromatic azines and hydrogen fluoride on the degree of aromaticity of these azines in considering the CH stretching region of its IR spectrum. Our results have revealed a lowering of the aromatic character of the azine ring. This corresponds to larger vibrational frequencies and smaller CH stretching intensities after complexation. An analysis based on a charge–charge flux-overlap model for infrared intensities indicates that this decrease on the intensity values is mainly due to the CH charge flux term. It becomes less negative upon the H-bond formation, whereas the hydrogen charge is only slightly increased. [Copyright &y& Elsevier]

Abstract: MP2/6-31++G(d,p) ab initio calculations have been performed to estimate the effect of the H-bond on the vibrational properties of HF due to its complexation with aromatic azines (C n N6-n H n , with n =5, 4 or 3). Our calculations have revealed that the greater is the number of nitrogen atoms in the aromatic ring, the smaller will be the HF stretching frequency downward shift and the increase of the H–F stretching intensity due to complexation. For example, the H–F frequency downward shift is 899cm−1 in pyridine-HF, whereas its corresponding value is 597cm−1 in 1,3,5-triazine-HF. Their infrared intensity ratios between the complexes and their corresponding monomers are 18.7 and 14.3cm−1, respectively. We have found a relationship between the HF stretching frequency downward shift and the number and position of the nitrogen atoms in the aromatic ring. As expected, the HF stretching intensity is enormously increased upon complexation and its value can be predicted by using the ∂P z /∂z H element of the hydrogen polar tensor, where z is the Cartesian axis along the H–F chemical bond. [Copyright &y& Elsevier]

Abstract: Ab initio molecular orbital calculations have been performed at the MP2/6-31++G** theoretical level in order to obtain molecular properties of hydrogen-bonded complexes involving pyrazine and the HX linear acids with, X=F, NC, Cl, CN, and CCH. Both the 1:1 and 1:2 adducts have been investigated, i.e., Pyz⋯HX and XH⋯Pyz⋯HX. The H-bond strength for these complexes can be interpreted in terms of the H–X stretching frequency downward displacement. This latter shows a good linear correlation with the intermolecular charge transfer and follows the order: X=F>X=NC>X=Cl>X=CN>X=CCH. As expected, the H–X stretching intensity is much enhanced upon H-bond formation. Here these effects on the HX infrared spectra are much more pronounced than those previously found in complexes with unsaturated hydrocarbons as proton acceptors. On the other hand, no important change has been verified in pyrazine, except the inhibition of the lone-pair trans effect from the lone-pair of nitrogen to the σ* antibonding orbital of the CC chemical bond in pyrazine. The new vibrational modes arising from complexation show several interesting features, specially the bending modes of the proton-donor molecule and the intermolecular stretching mode. [Copyright &y& Elsevier]

The molecular electrostatic potential (MEP) of the indole molecule was calculated in a three-dimensional grid in which the molecule was centered at the origin. To evaluate the dependence of MEP on the type of calculation, semiempirical, ab initio, and density functional theory methods with different basis sets were employed. The data matrix generated by these calculations was analyzed by principal component analysis (PCA). The appearance of outliers and the effect of wavefunction modifications such as the introduction of electron correlations and diffuse functions were highlighted by the use of PCA. The spatial localization of such effects around the molecule was possible from the loadings values associated with the graphical analysis of the grid points. [ABSTRACT FROM AUTHOR]

The stabilities of N-ethyl,N-methylformamide and N-ethyl,N-methylacetamide in their syn and anti forms have been calculated using HF/6-311++G**, MP2(FC)/6-311++G**//HF/6-311++G** and B3LYP/6-311++G**//HF/6-311++G** methods. The calculated NMR chemical shifts were evaluated using the last method. The relative position of the methyl part of the N-ethyl group has been found to be almost perpendicular to the plane of the heavy atoms in disagreement with the previous report. The conformational preference is discussed in terms of both steric and hyperconjugative/anomeric effects. The consequences of these effects on the geometry and NMR spectra have been analyzed. [Copyright &y& Elsevier]

RHF and MP2 ab initio molecular orbital calculations using the 4-31G** and 6-311G** basis sets have been employed to obtain Green''s function matrix elements (GD,A) and intermolecular charge transfers (ΔQcorr) of the CnNH…CnNH and CnNH…NCnH (n=1 and 3) hydrogen bonded complexes. Our calculations reveal that these two parameters are linearly correlated. Their values increase by effect of the addition of a C2 group to the proton donor and/or acceptor and when the hydrogen bonding is formed by the NH…C skeleton in comparison to the NH…N one. Our calculations have also revealed that the corresponding increments in GD,A and ΔQcorr due to change from NCH…NCH to CNH…NCH or from NCH…CNH to CNH…CNH are very similar. Finally, both GD,A and ΔQcorr show the same behavior when the hydrogen bonding distance is progressively increased from the equilibrium position until 4.5 A˚, forming two exponential curves practically superposed. Correlations between ΔE and ΔQcorr as well as ΔE and GD,A are also discussed. [Copyright &y& Elsevier]

Factorial design and principal component models are used to determine how ab initio H-bond energies depend on characteristics of the molecular orbital wave functions of HCN–HX linear complexes and acetylene–HX T-shaped complexes, with X=F, NC, Cl, CN and CCH. The results obtained for the two sets of complexes show that factorial design and principal component analyses complement each other. The H-bond energies of the HCN–HX linear complexes are affected mostly by adding polarization functions and by MP2 treatment, which have opposite signs. When polarization functions are introduced in the basis set the calculated H-bond energies decrease by  ≈4 kJ·mol−1. In contrast, when the level of calculation is changed from Hartree–Fock to MP2, the energies are increased by nearly the same amount on average. The principal component analysis shows that for the HCN–HX linear complexes the ab initio results are grouped into four well-separated classes: (I) HF calculations with polarization functions (HF/6-nG** and HF/6-n++G**), with n=31 or 311; (II) MP2 calculations without polarization functions (MP2/6-nG and MP2/6-n++G); (III) MP2 calculations including polarization functions (MP2/6-nG** and MP2/6-n++G**) and (IV) HF results without polarization functions (HF/6-nG and HF/6-n++G). The ab initio results of the group (III) are those that show a better agreement with the available experimental values. The change from the Hartree–Fock to the MP2 level is the most significant effect for the acetylene–HX complexes, increasing the calculated H-bond energy values by about 4.5 kJ·mol−1 on average. Here the ab initio results can be essentially grouped into two classes: HF or MP2 calculations. The H-bond energies calculated from the factorial models for the two sets of complexes are found to deviate only 6.5% from the full ab initio values. [Copyright &y& Elsevier]

Principal component analysis was used in the selection of the B3PW91/6-311+G(3df) method for calculations of As2O3 molecular species. This multivariate analysis compared experimental properties (structure and ionization energy) of As4O6 molecule with several computational methods (Hartree-Fock, second-order Møller-Plesset perturbation theory, and density functional theory) and basis sets. At the selected level of theory, we were able to calculate nine structures of As2O3 with three of them being stable ones (no negative force constants) in the following stability order: D3H (0.0), DIAMOND OUT (32.77 kJ mol−1), and GAUCHE (43.81 kJ mol−1). Several intramolecular conversions were studied with the GAUCHE → DIAMOND OUT transformation being barrierless, whereas the DIAMOND OUT structure is converted into the D3H isomer through a Gibbs free-energy barrier of 40.83 kJ mol−1. Starting from the GAUCHE structure of As2O3 and its enantiomeric form, it was possible to obtain directly (barrierless) the As4O6 species in a spontaneous process (Δr G = −399.92 kJ mol−1 at 298 K and 1 atm) in gas phase. Thus, the As4O6 species is probably the precursor of arsenic hydroxide through hydrolysis reactions. © 2012 Wiley Periodicals, Inc. [ABSTRACT FROM AUTHOR]

MP2/6-31++G(d,p) ab initio molecular orbital calculations have been employed to characterize hydrogen-bonded complexes between hydrogen fluoride as proton donor and aromatic azines (pyridine, pyrimidine, pyridazine, pyrazine, 1,3,5-triazine, and 1,2,4-triazine). Our calculations have shown that the H-bond strength in these complexes depends on both the number of nitrogen atoms as well as the position of these atoms in aromatic ring. The binding energies of azines-HF with or without BSSE and ZPE corrections decrease with the increasing number of nitrogen atoms in the ring. For example, its ΔEBSSE,ZPE value is 40.9 kJ · mol-1 in pyridine-HF, whereas its corresponding values in pyrazine-HF and 1,3,5-triazine-HF are 34.0 kJ · mol-1 and 26.6 kJ · mol-1, respectively. With respect to position of the nitrogen atom in the aromatic ring, the more pronounced effect is verified when it is at meta-position relative to the pyridine ring. There is a high linear correlation between the H-bond strength in these complexes and the intermolecular charge transfer using corrected Mulliken charges obtained from the charge-charge flux-overlap (CCFO) modified model for infrared intensities. Finally, our MP2/6-31++G(d,p) calculations have revealed that stronger hydrogen bonds are associated with smaller H-bond length values, larger intermolecular charge transfers and greater H&bond;F downward stretching frequency displacements. © 2006 Wiley Periodicals, Inc. Int J Quantum Chem, 2006 [ABSTRACT FROM AUTHOR]

This research aimed to record, for the first time, the damage caused by a pruner beetle on hybrid eucalypts cloned trees (Eucalyptus urophylla vs. E. grandis), located in Bahia and Espírito Santo States, Brazil. The specie was determined as Chalcodermus bicolor Fiedler, 1936 (Curculionidae: Molytinae). The female prunes the tree shoot and lays a single egg inside a small hole, just below the incision point. Eucalypt is the first host recorded to this pruner beetle specie. [ABSTRACT FROM AUTHOR]

The present manuscript reports a systematic investigation of the basis set dependence of some properties of hydrogen-bonded (π type) complexes formed by propyne and a HX molecule, where X=F, Cl and CN. The calculations have been performed at Hartree–Fock, MP2 and B3LYP levels. Geometries, H-bond energies and vibrational have been considered. The more pronounced effects on the structural parameters of the isolated molecules, as a result of complexation, are verified on RC≡C and HX bond lengths. As compared to double-ζ (6-31G**), triple-ζ (6-311G**) basis set leads to an increase of R C≡C bond distance, at all three computational levels. In the case where diffuse functions are added to both hydrogen and ‘heavy’ atoms, the effect is more pronounced. The propyne–HX structural parameters are quite similar to the corresponding parameters of acetylene–HX complexes, at all levels. The largest difference is obtained for hydrogen bond distance, R H, with a smaller value for propyne–HX complex, indicating a stronger bond. Concerning the electronic properties, the results yield the following ordering for H-bond energies, ΔE: propyne⋯HF>propyne⋯HCl>propyne⋯HCN. It is also important to point out that the inclusion of BSSE and zero-point energies (ZPE) corrections cause significant changes on ΔE. The smaller effect of ZPE is obtained for propyne⋯HCN at HF/6-311++G** level, while the greatest difference is obtained at MP2/6-31G** level for propyne⋯HF system. Concerning the IR vibrational it was obtained that larger shift can be associated with stronger hydrogen bonds. The more pronounced effect on the normal modes of the isolated molecule after the complexation is obtained for H–X stretching frequency, which is shifted downward. [Copyright &y& Elsevier]

Abstract: Configurational and conformational analysis were performed using ab initio and semi-empirical molecular orbital methods in order to obtain structural, electronic and energetic information about three previously synthesized imidazolidine derivatives, namely: 3-benzyl-5-benzylidene-imidazolidine-2,4-dione (5), 3-benzyl-5-benzylidene-2-thioxo-imidazolidine-4-one (6), 5-benzylidene-3-(2-oxo-2-phenyl-ethyl)-2-thioxo-imidazolidine-4-one (7) and other two new proposed imidazolidine derivatives: 3-benzyl-5-benzylidene-4-thioxo-imidazolidine-2-one (8) and 3-benzyl-5-benzylidene-imidazolidine-2,4-dithione (9). Important aspects related to structure activity relationship are highlighted. [Copyright &y& Elsevier]