Theoretical Study of the Structural and Electronic Properties of Luteolin and Apigenin Dyes.
ABSTRACT In this paper structure and electronic properties of luteolin and apigenin and all their possible anionic species have been
investigated with DFT and MP2 methods. Molecular geometries have been optimized obtaining for all systems non-planar structures
except for the deprotonated species in 4’ position. Potential energy proles as a function of the torsional angle between B
phenyl ring and 1,4-benzopyrone have been computed for luteolin and apigenin and their corresponding anionic species in 4’
position. Electronic structure for both neutral avonoids has been analyzed with DFT(B3LYP) investigating the frontier molecular
orbitals in terms of energy and character. Finally, changes on the electronical structure upon deprotonation have been evaluated.
- SourceAvailable from: Alfred Karpfen[Show abstract] [Hide abstract]
ABSTRACT: The fully relaxed single-bond torsional potentials in typical conjugated systems were evaluated with the aid of ab initio self-consistent-field and Møller−Plesset second-order calculations and, additionally, with several recently developed variants of the density functional theory. For this systematic investigation, 1,3-butadiene, styrene, biphenyl, 2,2‘-bithiophene, 2,2‘-bipyrrole and 2,2‘-bifuran have been selected as model molecules. As representative examples for nonconjugated systems, the molecules n-butane and 1-butene have been treated at the very same calculational levels. For all conjugated molecules, the electron correlation corrections to the self-consistent-field torsional potentials, as obtained with the density functional methods, are dramatically different from those resulting from the more conventional Møller−Plesset second-order approximation. For those cases where experimental data for torsional barriers are available, the self-consistent-field and the Møller−Plesset second-order results agree reasonably, whereas the density functional results consistently predict too large barriers. This behavior is most probably caused by an overestimation of the stability of the planar π-systems by the density functional theory variants in question.The Journal of Physical Chemistry A 01/1997; 101:7426. · 2.77 Impact Factor
- [Show abstract] [Hide abstract]
ABSTRACT: The height of the rotational barriers around C(pyridine)N(azide) single bond in azidopyridines has been determined via ab initio molecular orbital calculations. The optimized geometry obtained from RHF/6-31G∗∗ results was used as an input for a single-point MP2/6-31G∗∗ calculation, the results of which are reported in this work. The potential energy function of rotation was subjected to Fourier analysis and terminated nicely at V3 as is shown from the results of least square treatment. The s-cis conformer of 2-azidopyridine is slightly more stable than the s-trans conformer and both are more stable than others obtained during rotation. A transition state is identified and confirmed, during rotation, via the location of a stationary point through a saddle-point calculations. A Hessian-type run is carried out to calculate the frequency of vibration, only one imaginary, negative, frequency was obtained. The height of the rotational barrier of the azide group in 2-azidopyridine is the largest, about 7 kcal/mol, whereas it amounts 3.32 and 4.04 kcal/mol for 3-azido and 4-azidopyridine, respectively.Journal of Molecular Structure THEOCHEM 01/2007; 822:74-79. · 1.37 Impact Factor
- Journal of the Agricoltural and Food Chemistry. 01/2000; 48:3232-3250.