Testing of Exchange-Correlation Functionals of DFT for a Reliable Description of the Electron Density Distribution in Organic Molecules.

Researchers carrying out calculations using the DFT method face the problem of the correct choice of the exchange-correlation functional to describe the quantities they are interested in. This article deals with benchmark calculations aimed at testing various exchange-correlation functionals in terms of a reliable description of the electron density distribution in molecules. For this purpose, 30 functionals representing all rungs of Jacob's Ladder are selected and then the values of some QTAIM-based parameters are compared with their reference equivalents obtained at the CCSD/aug-cc-pVTZ level of theory.

Resonance-Assisted Hydrogen Bond-Revisiting the Original Concept in the Context of Its Criticism in the Literature.

In the presented research, we address the original concept of resonance-assisted hydrogen bonding (RAHB) by means of the many-body interaction approach and electron density delocalization analysis. The investigated molecular patterns of RAHBs are open chains consisting of two to six molecules in which the intermolecular hydrogen bond stabilizes the complex. Non-RAHB counterparts are considered to be reference systems.

Extremely Strong Halogen Bond. The Case of a Double-Charge-Assisted Halogen Bridge.

The stable model of a double (±)charge-assisted halogen bridge has been built on the basis of searches of the Crystal Structure Database. The model, investigated by DFT theory, consists of quinuclidine-like cation derivatives and a set of simple anions. These charged fragments form halogen-bonded complexes of which the energy of complexation in some cases reaches 100 kcal/mol.

Heteroatom and solvent effects on molecular properties of formaldehyde and thioformaldehyde symmetrically disubstituted with heterocyclic groups CHY (where Y = O-Po).

In this work several molecular properties of symmetrically disubstituted formaldehyde and thioformaldehyde have been studied using a quantum chemistry approach based on density functional theory. Five-membered heteroaromatic rings containing a single group 16 heteroatom were taken into account as the substituents (i.e.

UV-vis spectra of singlet state cationic polycyclic aromatic hydrocarbons: time-dependent density functional theory study.

A theoretical study of singlet state cations of polycyclic aromatic hydrocarbons is performed. Appropriate symmetry suitable for further calculations is chosen for each of the systems studied. The excitation states of such species are obtained by the time dependent density functional theory (TD-DFT) method.

The substituent effect on benzene dications.

It was recently postulated that the benzene ring and its 4n + 2 π-electron analogues are resistant to the substituent effect due to the fact that such systems tend to retain their delocalized character. Therefore, the 4n π-electron dicationic form of benzene should appear to be less resistant to the substituent effect, as compared with its parent neutral molecule. For this reason the effect of substitution on the dicationic form of benzene was thoroughly investigated and the consequences of single and double substitution (of para- and meta-type) were assessed by means of several parameters, including various aromaticity indices and the Substituent Effect Stabilization Energy (SESE) parameter.

C-H...N and C-H...S hydrogen bonds--influence of hybridization on their strength.

Simple complexes connected through C-H...

[Hepatitis B virus genotypes and the response to lamivudine therapy].

Hepatitis B virus (HBV) can be classified into eight major genotypes (A-H) that have mainly a geographic distribution. The HBV genotype may influence disease progression, HBeAg seroconversion rates, response to antiviral treatment. The aim of study was to analyze the distribution and frequency of genotypes in patients with chronic hepatitis B.

Synthesis, spectroscopy and antiproliferative activity of cis- and trans-platinum(II) complexes with diethyl (pyridin-4-ylmethyl)phosphate. X-ray crystal structure of trans-Pt(II) complex.

Preparations of cis- and trans-platinum(II) complexes of diethyl (pyridin-4-ylmethyl)phosphate (4-pmOpe) have been described. These complexes were identified and characterized by far-IR, 1H NMR, 13C NMR, 31P NMR and 195Pt NMR and microanalyses. The crystal and molecular structure of trans-platinum(II) complex i.

[Comparison of two commercial molecular assays for quantitative measurement of hepatitis B viral DNA].

The detection and quantification of hepatitis B virus (HBV) genomes appear to be the most reliable method for monitoring HBV infection and assessing responses to antiviral treatment. For quantitative determination of HBV viremia molecular biology-based assays are used. The aim of this study was to compare and evaluate the performance of two HBV DNA detection and quantification commercial assays: hybrid-capture Digene Hybrid Capture HBV DNA assays and based on competitive polymerase chain reaction (PCR) Cobas Amplicor HBV Monitor Roche Diagnostics.

1,3-thiazolidine derivatives from regioselective [2+3]-cycloadditions of azomethine ylides with thioketones.

The title compounds, namely dimethyl (2RS)-2,3-diphenyl-1,3-thiazolidine-5-spiro-2'-adamantane-4,4-dicarboxylate methanol solvate, C(28)H(31)NO(4)S.0.275CH(4)O, and dimethyl (4RS)-3,4-diphenyl-1,3-thiazolidine-5-spiro-9'-(9'H-fluorene)-2,2-dicarboxylate, C(31)H(25)NO(4)S, were obtained from dipolar [2+3]-cycloadditions of an azomethine ylide with adamantanethione and thiofluorenone, respectively.