Author(s): Qadir K Timerghazin

High-level ab initio calculations employing the CCSD and CCSD(T) coupled cluster methods with a series of systematically convergent correlation-consistent basis sets have been performed to obtain accurate molecular geometry and energetic properties of the simplest S-nitrosothiol (RSNO), HSNO. The properties of the S-N bond, which are central to the physio ...

Article GUID: 18327309

Author(s): Heidi M Muchall

We are presenting a computational study on the isotropic shielding, charge, and orbital contributions to the shielding of oxygen in benzaldehydes (Ar-CHO), nitrobenzenes (Ar-NO2), phenyl isocyanates (Ar-NCO), anilides (Ar-NHCOCH3), and N-sulfinylamines (Ar-NSO). In particular, changes upon ortho substitution of the aromatic ring and upon torsion of the un ...

Article GUID: 18754608

Author(s): Kamya PR; Muchall HM;

We have evaluated the performance of three (TD-)DFT functionals with the 6-31+G(d,p) basis set for the reproduction of experimental geometries, vertical ionization potentials, and low excitation energies of a selection of [2.2] and [3.3]paracyclophanes. Overall, (TD-)BH& H outperforms both (TD-)B3LYP and (TD-)PBE0. Some shortcomings are shown by B3LYP ...

Article GUID: 19055395

Author(s): Hernández de la Peña L; Peslherbe GH;

Nonequilibrium simulation methods and rigid-body path-integral techniques are combined to estimate the relevance of protonic quantum effects in the free energy of ion-water clusters. The Crooks' fluctuation relation is used to quantitatively characterize the impact of quantum effects on the dissociation free energy of the paradigm I(-)(H(2)O)(5). By u ...

Article GUID: 20377185

Author(s): Nguyen TN; Timerghazin QK; Vach H; Peslherbe GH;

Molecular electronic excitation in (O(2))(n) clusters induced by mechanical collisions via the "chemistry with a hammer" is investigated by a combination of molecular dynamics simulations and quantum chemistry calculations. Complete active space self-consistent field augmented with triple-zeta polarizable basis set quantum chemistry calculations of a comp ...

Article GUID: 21322678

Author(s): Ivanova EV; Muchall HM;

We present a computational study on the concerted hydrolysis of several classes of N-sulfinylamines of generic formula R-N-S-O, such as the -amines themselves (R-NSO), -hydrazines (R-NH-NSO), -hydrazides (R-CO-NH-NSO) and -amides (R-CO-NSO), as these species are known to possess a wide range of hydrolytic reactivity. Two possible mechanisms of hydrolysis, ...

Article GUID: 21428403

Author(s): Varadwaj PR; Varadwaj A; Marques HM;

A density functional theory study of the structure of the title compounds with the divalent metal ions in their high-spin ground state, obtained using B3LYP/6-311++G(d,p) in vacuo and in aqueous solution simulated using a polarized continuum medium, is reported for the first time. The modeling reproduces the pseudo pentagonal bipyramidal crystallographic ...

Article GUID: 21568260

Author(s): Kamya PR; Muchall HM;

Calculated electron densities from PBE0/6-31+G(d,p) were analyzed with respect to the hydrogen bonding within a nucleic acid base pair and the p-stacking between sets of base pairs. From published X-ray crystallographic data, base pairs were isolated from a total of 11 DNA and RNA duplexes, and their experimental geometry was maintained throughout the ana ...

Article GUID: 21721560

Author(s): Varadwaj PR; Varadwaj A; Peslherbe GH; Marques HM;

Density functional theory calculations, together with quantum theory of atoms in molecules (QTAIM) analyses, have been performed to investigate 18-azacrown-6 complexes of the high-spin late first transition series divalent metal ions in the gas phase and, in some cases, in aqueous solution simulated by a polarizable continuum model. Six intramolecular H-H ...

Article GUID: 21961695

Author(s): Heidi M Muchall

Nitrilimines (R-CNN-R) can be described through a carbenic valence bond structure, and although intermolecular carbenic reactions from nitrilimines are unknown, intramolecular reaction products from ortho-vinyl MeCOO-CNN-Ph (1) and Ph-CNN-Ph (2) that seem to have followed two typical carbene reaction mechanisms, [1+2] cycloaddition and C-H insertion, have ...

Article GUID: 21974693

Author(s): Mak CC; Timerghazin QK; Peslherbe GH;

Upon photoexcitation of iodide-water clusters, I(-)(H(2)O)(n), an electron is transferred from iodide to a diffuse cluster-supported, dipole-bound orbital. Recent femtosecond photoelectron spectroscopy experiments have shown that, for photoexcited I(-)(H(2)O)(n) (n= 5), complex excited-state dynamics ultimately result in the stabilization of the transferr ...

Article GUID: 22466252

Author(s): Wang S; Orabi EA; Baday S; Bernèche S; Lamoureux G;

Proteins of the Amt/MEP family facilitate ammonium transport across the membranes of plants, fungi, and bacteria and are essential for growth in nitrogen-poor environments. Some are known to facilitate the diffusion of the neutral NH(3), while others, notably in plants, transport the positively charged NH(4)(+). On the basis of the structural data for Amt ...

Article GUID: 22631217