Study of the Chelating Capacity of Nucleobase Analogs with Biological Interest: Ab initio Molecular Orbital Calculations and Single-Crystal X-ray Structural Study of 6-Amino-5-formyl-1,3-dimethyluracil-benzoylhydrazone

2000 ◽  
Vol 6 (12) ◽  
pp. 630-636 ◽  
Author(s):  
Francisco Hueso-Ureña ◽  
Miguel N. Moreno-Carretero ◽  
Antonio L. Peñas-Chamorro ◽  
Tomás Peña ◽  
José M. Amigó ◽  
...  
Keyword(s):  
Single Crystal ◽  
Ab Initio ◽  
Molecular Orbital ◽  
Structural Study ◽  
Molecular Orbital Calculations ◽  
X Ray ◽  
Biological Interest

Adaptation of the Gelius intensity model in semiempirical HAM/3 molecular orbital calculations of valence photoelectron spectra excited by X-ray radiation

1985 ◽  
Vol 63 (7) ◽  
pp. 2007-2011 ◽  
Author(s):  
Delano P. Chong
Keyword(s):  
Ab Initio ◽  
Molecular Orbital ◽  
Cross Sections ◽  
Present Method ◽  
Photoelectron Spectra ◽  
Molecular Orbital Calculations ◽  
Ionization Energies ◽  
X Ray ◽  
Hartree Fock ◽  
Intensity Model

The Gelius intensity model has been adapted in the semiempirical HAM/3 method to calculate the valence ionization energies and intensities in XPS. Both semiempirical and àb initio Hartree–Fock–Slater atomic photoionization cross-sections can be used. Results presented for C2H2, C2H4, N2, H2O, CH3OH, and CH2F2 demonstrate that the present method can facilitate the interpretation of experimental XPS.

Solvation Structure of Solvated Cu(I) Ions in Non-Aqueous Solvents as Studied by EXAFS and ab initio Molecular Orbital Methods

1999 ◽  
Vol 54 (2) ◽  
pp. 193-199 ◽  
Author(s):  
Y. Inada ◽  
Y. Tsutsui ◽  
H. Wasada ◽  
S. Funahashi
Keyword(s):  
Ab Initio ◽  
Molecular Orbital ◽  
Steric Effect ◽  
Molecular Orbital Calculations ◽  
Enthalpy Of Solvation ◽  
Octahedral Structure ◽  
X Ray ◽  
Solvation Structure ◽  
Solvent Molecules ◽  
X Ray Absorption

The structure parameters around the Cu(I) ion in pyridine (PY), 4-methylpyridine (4MPY), 2-methylpyridine (2MPY), 2,6-dimethylpyridine (26DMPY), and acetonitrile (AN) were determined by the extended X-ray absorption fine structure (EXAFS) method. The solvation structures of the Cu(I) ion in PY, 4MPY, and AN are 4-coordinate tetrahedral with Cu-N bond lengths of 205, 205, and 200 pm, respectively. In the case of 2MPY and 26DMPY, the Cu(I) ion has a 3-coordinate triangular structure with a Cu-N bond length of 201 pm. Such a decrease in the coordination number was interpreted in terms of the bulkiness of the solvent molecules. In order to clarify the most stable solvation structure of the Cu(I) ion, we carried out ab initio molecular orbital calculations for the solvation system of [Cu(NCH)n]+ (n = 1 - 6 ) where the steric effect is negligible. The Gibbs free energy of solvation was the smallest in the case of n = 4 and the 4-coordinate tetrahedral solvation of the Cu(I) ion was theoretically evaluated as most stable. The enthalpy of solvation monotonously decreases with increasing n, while the entropy of solvation proportionally increases. Although a larger gain of enthalpy is observed for the octahedral structure rather than the tetrahedral one, the entropic loss for the former overcomes the enthalpic gain.

Sign in / Sign up

Export Citation Format

Share Document