Aqueous solvent effects on the conformational space of tryptamine. Structural and electronic analysis.

The TRA (3-[2-aminoethyl]indole) is an important neurotransmitter with a close structural and chemical similarity to the neurotransmitter serotonin (5-hydroxytryptamine), and to melatonin (5-methoxy-N-acetyltryptamine), which plays a key role in daily human behavior. Moreover, TRA, and other indolic compounds are very efficient antioxidants. In this work the conformational space of TRA was scanned in aqueous solution, simulating the solvent by the polarizable continuum model.

QSPR Study of Valproic Acid and Its Functionalized Derivatives.

This work establishes a Quantitative Structure-Property Relationships (QSPR) based analysis with the aim of interpreting both the structural and electronic properties of the polar region of valproic acid and its derivatives, in terms of stabilizing intramolecular interactions related to the involved substituents. We consider ten different calculated properties as dependent variables for the QSPR models: the bond lengths C8 O9 , C8 X10 , and the percentage of s-character of the natural hybrids forming the bonding σ orbitals of the O9 C8 X10 region. The representative descriptors are the charges transferred during donor/acceptor interactions around this function calculated at the B3LYP/6-311++G**(6d,10f) level of theory, and/or hybrid descriptors derived therefrom.

Conformational and stereoelectronic investigation of tryptamine. An AIM/NBO study.

Unlabelled: Due to the free radical scavenger properties of Tryptamine (TRA), as well as of others indole derivatives, it is in our interest to explore deeply the stereoelectronic aspects that would be relevant in their stabilization and antioxidant activity. In this work the conformational space of TRA was scanned using molecular dynamics complemented with functional density calculations at B3LYP/6-31 + G** level. Twenty one conformers of lowest energy were obtained, their electronic distributions were analyzed at a higher calculation level, thus improving the basis set (B3LYP/6-311++G**).

Structural and electronic properties of Z isomers of (4α→6´´,2α→O→1´´)-phenylflavans substituted with R = H, OH and OCH₃ calculated in aqueous solution with PCM solvation model.

In the search for new antioxidants, flavan structures called our attention, as substructures of many important natural compounds, including catechins (flavan-3-ols), simple and dimeric proanthocyanidins, and condensed tannins. In this work the conformational space of the Z-isomers of (4α→6´´, 2α→O→1´´)-phenylflavans substituted with R = H, OH and OCH(3) was scanned in aqueous solution, simulating the solvent by the polarizable continuum model (PCM). Geometry optimizations were performed at B3LYP/6-31 G level.

Topological properties of some PhSeX compounds.

A theoretical study on the series of compounds "PhSeX", where Ph = phenyl, Se = selenium and X = Cl, Br, I, CN or SCN, is reported and compared with previously reported experimental data. The molecular geometry for these PhSeX compounds was studied at the DFT/B3LYP level of calculation by means of the 6-311G(d,p) basis set. The equilibrium structures of the molecules were dependent on the method employed to compare the known solid structures.

Study of the structural and electronic properties of valproic acid and new derivatives used as anticonvulsant agents.

The conformational and electronic characteristics of the polar O(9)═C(8)-X(10) moiety in the anticonvulsant valproic acid (Vpa) drug and some of their amides and ester derivatives are analyzed at the B3LYP level using the 6-31+G(d,p) and 6-311++G(d,p) 6d,10f basis sets. Exploring the delocalization of the electron density of the O(9)═C(8)-X(10) moiety by means of ELF, NBO, and AIM calculations, we found that the bending away from coplanarity of the atoms in O(9)═C(8)-X(10) is accompanied by a three-dimensional arrangement of donor and acceptor proton units closing nearly planar pseudorings of four, five, and six members arising from stabilizing interactions around the O(9)═C(8)-X(10) backbone. From the structure-property relationship analysis, we explain the origin of the change in the structural parameters and atomic charges in the polar moiety.

Theoretical studies and vibrational spectra of 1H-indole-3-acetic acid. Exploratory conformational analysis of dimeric species.

Theoretical studies on 1H-indole-3-acetic acid (IAA) were performed to investigate the conformational properties of dimeric species and vibrational spectra. Experimental infrared spectra at 100 K and 297 K and Raman spectrum at 297 K were analyzed and compared against calculations performed at B3LYP/6-31G** level. A exploratory study of the conformational space of dimeric species was performed.

Electronic structure and conformational properties of 1H-indole-3-acetic acid.

Unlabelled: The conformational space of 1H-Indole-3-Acetic Acid (IAA) was scanned using molecular dynamics at semiempirical level, and complemented with functional density calculations at B3LYP/6-31G** level, 14 conformers of lowest energy were obtained. Electronic distributions were analyzed at a higher calculation level, thus improving the basis set (B3LYP/6-311++G**). A topological study based on Bader's theory (

Aim: atoms in molecules) and natural bond orbital (NBO) framework performed with the aim to analyze the stability and reactivity of the conformers allowed the understanding of electronic aspects relevant in the study of the antioxidant properties of IAA.

Theoretical study of Z isomers of A-type dimeric proanthocyanidins substituted with R=H, OH and OCH₃: stability and reactivity properties.

The stereochemistry of A-type dimeric proanthocyanidins was studied, focusing on the factors that determine it, and the changes that occur with R = OCH₃, R' = H, and R = OH, R' = H as substituents, starting with the study of the conformational space of each species. Using molecular dynamics at a semiempirical level, and complementing with functional density calculations, two conformers of lowest energy were characterized for R = H, eight conformers for R = OH, and three conformers for R = OCH₃. Electronic distributions were analyzed at a higher calculation level, thus improving the basis set.

Theoretical characterization of SOME amides and esters DERIVATIVES of valproic acid.

The equilibrium structures, the planarity of the C(=O)X linkage and the nature of the chemical bond in the Y-C(=O)-XR(1)R(2) [where: Y= -CH-(CH(2)-CH(2)-CH(3))(2), X=N,O and R(1), R(2)= H; alkyl and aryl groups and lone pair electrons (lp)] molecular fragment of derivates of Valproic acid (Vpa) with antiepileptic activity were studied systematically by means of B3LYP calculations and topological analysis of the electron localization function (ELF). The covariance parameter cov[Omega(i), Omega(j)] reveals a dominating delocalization effect between the lone pair V(O(1)), V(X) and the electron density of the H-C and H-X(1) bonds resulting from the existence of not only non-conventional intramolecular hydrogen bonding patterns as C-H..

Conformational and electronic (AIM/NBO) study of unsubstituted A-type dimeric proanthocyanidin.

Unlabelled: The conformational space of the unsubstituted A-type dimeric proanthocyanidin was scanned using molecular dynamics at a semiempirical level, and complemented with functional density calculations. The lowest energy conformers were obtained. Electronic distributions were analysed at a higher calculation level, thus improving the basis set.

Spectroscopic and theoretical study of 2-acetylphenyl-2-naphthoate.

Mid-, far-infrared and Raman vibrational spectra of 2-acetylphenyl-2-naphthoate have been measured at room and low temperatures. The molecule was also analyzed by means of ab initio calculations. The conformational space has been scanned using molecular dynamics and complemented with functional density calculations that optimize the geometry of the lowest energy conformers 2-acetylphenyl-2-naphthoate as obtained in the simulations.

Vibrational spectra, NMR and theoretical studies of the enantiomers and rotamers of alpha-cypermethrin.

NMR, infrared and Raman vibrational spectra of alpha-cypermethrin have been measured at room temperature. Infrared spectra were also recorded to low temperature. The spectra were analyzed by means of ab initio calculations.

Study of the Topological Properties of Some Pseudohalides.

The pseudohalide principle has been used extensively in nonmetal chemistry to predict the structure and stability of many molecular species. The 1,2,3,4-thiatriazole-5-thiolate anion, CS2N3(-), is of particular interest. In a short communication we have recently reported the topological study of some CS2N3(-)containing species reported by Crawford et al.

Three-center-two-electron and four-center-four-electron bonds. A study by electron charge density over the structure of methonium cations.

We study the electronic density charge topology of CH(5)(+) species 1 (C(s)()), 2 (C(s)()), and 3 (C(2)(v)) at ab initio level using the theory of atoms in molecules developed by Bader. Despite the reports of previous studies concerning carbocationic species, the methane molecule is protonated at the carbon atom, which clearly shows its pentacoordination. In addition to the fact that hydrogen atoms in the methonium molecule behave in a very fluxional fashion and that the energy difference among the species 1, 2, and 3 are very low, is important to point out that two different topological situations can be defined on the basis of our study of the topology of the electronic charge density.

Some electronic correlation effects in the topological analysis of the Laplacian of the electronic charge density in C-n-butonium cations.

In this work, we present a topological study of the Laplacian of the electronic density using a 6-311++G basis set, at Hartree-Fock (HF) and second-order Møller-Plesset (MP2) (full-electron and frozen-core) levels of theory, for the carbocations 2-C-n-butonium generated upon the insertion of a proton into the secondary C-C bond during the protonation of n-butane. The charge concentration, CC, critical points of the Laplacian distribution at each valence shell, VS, of carbon atoms, and the charge concentration closer to hydrogen atoms are studied. Also, the bonding critical points of the electronic density are analyzed.