Adiabatic ionization energies, bond disruption enthalpies, and solvation free energies for gas-phase metallocenes and metallocenium ions

1992 ◽  
Vol 114 (22) ◽  
pp. 8611-8619 ◽  
Author(s):  
Matthew F. Ryan ◽  
John R. Eyler ◽  
David E. Richardson
Keyword(s):  
Gas Phase ◽  
Free Energies ◽  
Ionization Energies ◽  
Solvation Free Energies ◽  
Bond Disruption

2-Deoxyribose Radicals in the Gas Phase and Aqueous Solution. Transient Intermediates of Hydrogen Atom Abstraction from 2-Deoxyribofuranose

2005 ◽  
Vol 70 (11) ◽  
pp. 1769-1786 ◽  
Author(s):  
Luc A. Vannier ◽  
Chunxiang Yao ◽  
František Tureček
Keyword(s):  
Aqueous Solution ◽  
Hydrogen Atom ◽  
Gas Phase ◽  
Computational Study ◽  
Hydrogen Atom Abstraction ◽  
Oh Radical ◽  
Free Energies ◽  
Intramolecular Hydrogen ◽  
Solvation Free Energies ◽  
Transient Intermediates

A computational study at correlated levels of theory is reported to address the structures and energetics of transient radicals produced by hydrogen atom abstraction from C-1, C-2, C-3, C-4, C-5, O-1, O-3, and O-5 positions in 2-deoxyribofuranose in the gas phase and in aqueous solution. In general, the carbon-centered radicals are found to be thermodynamically and kinetically more stable than the oxygen-centered ones. The most stable gas-phase radical, 2-deoxyribofuranos-5-yl (5), is produced by H-atom abstraction from C-5 and stabilized by an intramolecular hydrogen bond between the O-5 hydroxy group and O-1. The order of radical stabilities is altered in aqueous solution due to different solvation free energies. These prefer conformers that lack intramolecular hydrogen bonds and expose O-H bonds to the solvent. Carbon-centered deoxyribose radicals can undergo competitive dissociations by loss of H atoms, OH radical, or by ring cleavages that all require threshold dissociation or transition state energies >100 kJ mol-1. This points to largely non-specific dissociations of 2-deoxyribose radicals when produced by exothermic hydrogen atom abstraction from the saccharide molecule. Oxygen-centered 2-deoxyribose radicals show only marginal thermodynamic and kinetic stability and are expected to readily fragment upon formation.

scholarly journals Nanostructures of PAMAM Dendrimers in Drug Delivery System for 5-Fluorouracil

2020 ◽  
pp. 309-323
Author(s):  
Fatemeh Haghighi ◽  
Ali Morsali ◽  
Mohammad R. Bozorgmehr ◽  
S. Ali Beyramabadi
Keyword(s):  
Gas Phase ◽  
Molecular Descriptors ◽  
Pamam Dendrimers ◽  
Stable Configuration ◽  
Free Energies ◽  
Quantum Molecular Descriptors ◽  
Solvation Energies ◽  
Reduced Toxicity ◽  
Solvation Free Energies ◽  
Binding Free Energies

In this article, we studied five noncovalent structures for adsorption of 5 fluorouracil drug (5 FL) on poly(amidoamine) G0 generation dendrimer (PAMAMG0) carrier using M06-2X and B3LYPfunctionals. We investigate the quantum molecular descriptors and the binding and solvation energies in gas phase and aqueous solution. The energetic stability of non-bonded species (PAMAMG0/5-FL1-5) was shown through evaluation of binding free energies. The solvation free energies of PAMAMG0/5-FL1-5 are negative, indicating that the solvation process is spontaneous. We considered quantum molecular descriptors such as electrophilicity power and global hardness and found reduced toxicity of 5-FL drug near PAMAMG0 carrier as well as facilitated drug release. The AIM (Atoms In Molecule) analysis for all PAMAMG0/5-FL1-5 structures demonstrated that the pseudo-hydrogen and hydrogen bonds are essential in the functionalization of PAMAMG0 with 5-FL drug. We found thatthe structure in which 5-FL drug interacts with CO functional groups of PAMAMG0 is the most stable configuration

A QM/MM study combined with the theory of energy representation: Solvation free energies for anti/syn acetic acids in aqueous solution

2006 ◽  
Vol 419 (1-3) ◽  
pp. 240-244 ◽  
Author(s):  
Takumi Hori ◽  
Hideaki Takahashi ◽  
Masayoshi Nakano ◽  
Tomoshige Nitta ◽  
Weitao Yang
Keyword(s):  
Aqueous Solution ◽  
Free Energies ◽  
Solvation Free Energies ◽  
Acetic Acids

THEORETICAL CALCULATION OF pKb VALUES FOR ANILINES AND SULFONAMIDE DRUGS IN AQUEOUS SOLUTION

2012 ◽  
Vol 11 (02) ◽  
pp. 283-295 ◽  
Author(s):  
BAHRAM GHALAMI-CHOOBAR ◽  
ALI GHIAMI-SHOMAMI ◽  
PARIA NIKPARSA
Keyword(s):  
Gas Phase ◽  
Continuum Model ◽  
Correlation Equation ◽  
Polarizable Continuum Model ◽  
Free Energies ◽  
Pcm Model ◽  
Solvation Models ◽  
Polarizable Continuum ◽  
Better Than ◽  
Good Agreement

In this work, calculations of p K b values have been performed for aniline and its substituted derivatives and sulfonamide drugs by using Gaussian 98 software package. Gas-phase energies were calculated with HF /6-31 G ** and B3LYP /6-31 G ** levels of theory. Free energies of solvation have been computed using the polarizable continuum model (PCM), conductor-like polarizable continuum model (CPCM) and the integral equation formalism-polarizable continuum model (IEFPCM) at the same levels which have been used for geometry determination in the gas-phase. The results show that the calculated p K b values using the B3LYP /6-31 G ** are better than those using the corresponding HF /6-31 G **. At first, the correlation equation was found to determine the p K b values of the investigated anilines. Then, this correlation equation was used to calculate the p K b values of the sulfonamide drugs. The results obtained indicate that the PCM model is a suitable solvation model for calculating p K b values in comparison to the other solvation models. For the investigated compounds a good agreement between the experimental and the calculated p K b values was also observed.

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