Search results for "DFT CALCULATION"

Effects of the net charge on abundance and stability of supramolecular surfactant aggregates in gas phase

2011

Self-assembling of amphiphilic molecules under electrospray ionization (ESI) conditions is characterized by quite unexpected phenomenology. The noticeable differences with respect to the condensed phase are attributable to the absence of the surfactant-solvent interactions, the presence of net charge in the aggregates, and the strong deviation from equilibrium conditions. Aiming to investigate the effects of the net charge on abundance and stability of supramolecular surfactant aggregates, positively and negatively charged aggregates of sodium bis(2-ethylhexyl)sulfosuccinate (AOT) and sodium methane sulfonate (MetS), butane sulfonate (ButS) and octane sulfonate (OctS) have been studied by E…

Reactions of m-Terphenyl-Stabilized Germylene and Stannylene with Water and Methanol: Oxidative Addition versus Arene Elimination and Different React…

2015

Reactions of the divalent germylene Ge(ArMe6)2 (ArMe6 = C6H3-2,6-{C6H2-2,4,6-(CH3)3}2) with water or methanol gave the Ge(IV) insertion product (ArMe6)2Ge(H)OH (1) or (ArMe6)2Ge(H)OMe (2), respectively. In contrast, its stannylene congener Sn(ArMe6)2 reacted with water or methanol to produce the Sn(II) species {ArMe6Sn(μ-OH)}2 (3) or {ArMe6Sn(μ-OMe)}2 (4), respectively, with elimination of ArMe6H. Compounds 1–4 were characterized by IR and NMR spectroscopy as well as by X-ray crystallography. Density functional theory calculations yielded mechanistic insight into the formation of (ArMe6)2Ge(H)OH and {ArMe6Sn(μ-OH)}2. The insertion of an m-terphenyl-stabilized germylene into the O–H bond was…

Hydrogenation of but-2-yne-1,4-diol on a palladium cluster: a computational study

2013

Structure and properties of N-methyl-N-(4-pyridyl)-nitramine and 1,4-dihydro-1-methyl-4-nitriminopyridine

2002

Abstract The molecular structure and spectral properties of N -methyl- N -(4-pyridyl)-nitramine ( 1 ) and 1,4-dihydro-1-methyl-4-nitriminopyridine ( 3 ) were investigated by the X-ray diffraction, FTIR, nuclear magnetic resonance (NMR) methods and DFT theoretical calculations. N -methyl- N -(4-pyridyl)-nitramine ( 1 ) crystallises in the orthorhombic Pbca space group. It is composed of two planar fragments; nitramino (N 2 O 2 ) group and the pirydyl ring. These two groups are twisted at about 70° with respect to each other, along the Ar–N bond. On the contrary, in compound 3 , they are coplanar to each other. Twist of the nitramino group in 1 with respect to the pirydyl ring leads to a sign…

B-DNA Structure and Stability as Function of Nucleic Acid Composition. Dispersion-Corrected DFT Study of Dinucleoside-Monophosphate Single and Double…

2013

actions of the sugar-phosphate skeleton with water; (6) hydrophobic interactions of the DNA cylindrical core, made up by the hydrogen-bonded and stacked nitrogen bases, with the water solvent. Recently, there has been increasing effort in developing and applying quantum chemical methods able to reproduce the structure of native B-DNA and to correctly describe the energy involved in the intrastrand and interstrand noncovalent interactions between the nucleotide monomers. This topic has been approached by both wave function methods and density functional theory. [2] Water solvent and sodium counterions also play an important role in the formation and relative stabilization of the double-helic…

Magneto-structural correlations and DFT calculations in two rare tetranuclear copper(II)-clusters with doubly phenoxo and end-on azido bridges: Synth…

2010

International audience; By slightly changing the synthetic conditions, we have prepared two closely related linear tetranuclear CuII complexes with the symmetrical ONNO donor tetradentate Schiff-base ligand [H2L = (OH)C6H4(CH3)Cdouble bond; length as m-dashN(CH2)3Ndouble bond; length as m-dashC(CH3)C6H4(OH)] and with azide ions. These two distinctly coloured crystalline products were characterized by elemental analysis, IR and UV–Vis spectroscopy, CV, EPR spectra and variable temperature magnetic measurements. Single crystal X-ray diffraction studies of the green [Cu4(μ-L)2(μ1,1-N3)2(N3)2] (1) and the red [Cu4(μ-L)2(μ1,1-N3)2(N3)2(H2O)2] (2) crystals show that the coordination environment o…

Substituent effects in nitro derivatives of carbazoles investigated by comparison of low-temperature crystallographic studies with density functional…

2014

The crystal structure of 9H-carbazole, C12H9N, (I), has been redetermined at low temperature for use as a reference structure in a comparative study with the structures of 1-nitro-9H-carbazole, C12H8N2O2, (II), and 9-nitrocarbazole, C12H8N2O2, (III). The molecule of (I) has crystallographically imposed mirror symmetry (Z′ = 0.5). All three solid-state structures are slightly nonplanar, the dihedral angles between the planes of the arene and pyrrole rings ranging from 0.40 (7)° in (III) to 1.82 (18)° in (II). Nevertheless, a density functional theory (DFT) study predicts completely planar conformations for the isolated molecules. To estimate the influence of nitro-group substitution on aroma…

The effect of β‐methylation on the conformation of α, β‐dehydrophenylalanine: a DFT study

2009

Dehydroamino acids are non‐coded amino acids that offer unique conformational properties. Dehydrophenylalanine (ΔPhe) is most commonly used to modify bioactive peptides to constrain the topography of the phenyl ring in the side chain, which commonly serves as a pharmacophore. The Ramachandran maps (in the gas phase and in CHCl3 mimicking environments) of ΔPhe analogues with methyl groups at the β position of the side chain as well as at the C‐terminal amide were calculated using the B3LYP/6‐31 + G** method. Unexpectedly, β‐methylation alone results in an increase of conformational freedom of the affected ΔPhe residue. However, further modification by introducing an additional methyl group a…

Gas phase behavior of radical cations of perfluoroalkyl-1,2,4-triazines: an experimental and theoretical study

2009

Electron ionization mass spectrometry and low-energy collision-induced decomposition reactions occurring in a tridimensional ion trap, together with density functional theory (DFT) calculations on neutrals, even- and odd-electron cations, have been used to study the gas-phase ion chemistry of a series of perfluoroalkyl-1,2,4-triazines. Loss of oxygen, due to thermal degradation occurring before ionization, likely involving the hydroxylamino group, has been observed. Compounds having a carbonyl group at position 6 of the triazine ring fragment in the source by elimination of NO followed by HF or CO. The decomposition pathways occurring due to CID experiments have shown interesting features d…

Recent developments and applications of the chiral Brønsted acid catalyzed allylboration of carbonyl compounds

2018

The 50-year-old allylboration reaction has seen dramatic developments since the dawn of the new century after the first catalytic asymmetric versions came into play. In the past decade alone, several methodologies capable of achieving the desired homoallylic alcohols in over 90% ee have been developed. This review focuses on the chiral Brønsted acid catalyzed allylboration reaction, covering everything from the very first examples and precedents to modern day variations and applications.1 Introduction2 Early Developments3 Synthetic Applications4 Variants5 Computational Contribution6 Conclusions