The structure of quinuclidine, HC(CH(2)CH(2))(3)N, has been re-investigated by quantum chemical calculations and by gas-phase electron diffraction (GED). The GED data, together with published rotational constants, have been analysed using the SARACEN method to determine the most reliable structure (r(h1)) for the gaseous molecule. The structures of two adducts of quinuclidine with group 13 trih...

The tautomerism of curcumin has been investigated in ethanol/water binary mixtures by using UV-Vis spectroscopy and advanced quantum-chemical calculations. The spectral changes were processed by using advanced chemometric procedure, based on resolution of overlapping bands technique. As a result, molar fractions of the tautomers and their individual spectra have been estimated. It has been show...

In this paper the stereostructural investigation of two new oxygenated polyketides, plakilactones G and H, isolated from the marine sponge Plakinastrella mamillaris collected at Fiji Islands, is reported. The stereostructural studies began on plakilactone H by applying an integrated approach of the NOE-based protocol and quantum mechanical calculations of (13)C chemical shifts. In particular, p...

We report a molecular simulation study of the c~432! superlattice structure of alkanethiols on Au~111! based on an accurate force field developed from ab initio quantum chemical calculations. Quantum chemical calculations were performed on both clusters and periodic systems of methylthiols on Au~111! surfaces. Molecular mechanics and dynamics simulations of alkanethiols with various chain lengt...

The accurate and reliable prediction of properties of molecules typically requires computationally intensive quantum-chemical calculations. Recently, machine learning techniques applied to ab initio calculations have been proposed as an efficient approach for describing the energies of molecules in their given ground-state structure throughout chemical compound space (Rupp et al. Phys. Rev. Let...

The photoelectron photoemission spectra and thresholds for low coverages of Li and K adsorbed on water-ice have been measured, compared with photoionization spectra of the gas-phase atoms, and modeled by quantum chemical calculations. For both alkali metals the threshold for photoemission is dramatically decreased and the cross section increased on adsorption to the water-ice surface. Quantum c...

In order to obtain accurate results from quantum chemical calculations on systems containing heavy atoms, relativistic effects must be accounted for in a most straightforward way. This can be achieved via the fourcomponent formulation applying original Dirac formalism with almost no approximations. Due to a considerable software development effort in recent years, two of those quantum chemical ...

Decomposition of activation free energies of chemical reactions, into enthalpic and entropic components, can provide invaluable signatures of mechanistic pathways both in solution and in enzymes. Owing to the large number of degrees of freedom involved in such condensed-phase reactions, the extensive configurational sampling needed for reliable entropy estimates is still beyond the scope of qua...

D-glucose derivatives of dihydropyrido-[2,3-d:6,5-d']-dipyrimidine-2, 4, 6, 8(1H,3H, 5H,7H)-tetraone (GPHs) have been synthesized and investigated as corrosion inhibitors for mild steel in 1M HCl solution using gravimetric, electrochemical, surface, quantum chemical calculations and Monte Carlo simulations methods. The order of inhibition efficiencies is GPH-3 > GPH-2 > GPH-1. The results furth...