Conformational and Substitution Effects on the Electron Distribution in a Series of Anthocyanidins

Estévez, Laura; Mosquera, Ricardo A.

doi:10.1021/jp904298z

Cited by 21 publications

(33 citation statements)

References 40 publications

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“…This avoids important steric hindrances (C2‐C3‐O3‐CH3 in ‐ anti and C6‐C5‐O5‐CH3 in ‐ syn ). In previous studies, it has been found that the most stable anionic form of cyanidin is obtained extracting protons from hydroxyls bonded to C5 and C4’ . The near isoenergetic anion A74’ (that obtained by extracting protons of C7‐OH and C4’‐OH) would be the most stable in cyanidin‐3,5‐ O ‐dimethoxide.…”

Section: Methodsmentioning

confidence: 98%

Complexation of common metal cations by cyanins: Binding affinity and molecular structure

Estévez

Sánchez‐Lozano

Mosquera

2018

Int J of Quantum Chemistry

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The ability of diverse metal cations to form complexes with cyanin has been investigated by means of Density Functional Theory (DFT) and the Quantum Theory of Atoms in Molecules (QTAIM). The strongest preference is shown by trivalent metals which exceed that of Mg(II), indicating that ion replacement processes are suitable detoxification mechanisms for plants. Molecular structure analysis indicates that the larger the metal affinity of Cy− the longer the C2‐C1’ bond length and smaller ρb value. This is understood as upon metal complexation the Cy− ligand molecular structure is more compatible with a dienolate‐like structure rather than the 4′‐keto‐quinoidal‐like structure. The weight of the former increases as stronger the binding. QTAIM charges indicate that the stronger the binding energy the larger the charge transfer from Cy− to the metal, reducing its positive charge below the values indicated by the corresponding Lewis structure.

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Section: Methodsmentioning

confidence: 98%

Complexation of common metal cations by cyanins: Binding affinity and molecular structure

Estévez

Sánchez‐Lozano

Mosquera

2018

Int J of Quantum Chemistry

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“…A density functional theory (DFT) and polarized continuum model (PCM) study of cationic, quinoidal and anionic forms of pelargonidin in aqueous and gas state was performed to obtain structures and respective ionization potentials . Localization of positive or negative charge in charged anthocyanidins was examined by DFT and PCM methods by the same authors . A study of conformers of portisins (vinylphenolpyranoanthocyanins) using comparison of experimental NMR and theoretical computational data was published .…”

Section: Introductionmentioning

confidence: 99%

“…[17] Localization of positive or negative charge in charged anthocyanidins was examined by DFT and PCM methods by the same authors. [18] A study of conformers of portisins (vinylphenolpyranoanthocyanins) using comparison of experimental NMR and theoretical computational data was published. [19] In another study, experimental NMR shielding constants for nine anthocyanidins in solid state were compared with data collected from DFT calculations.…”

Section: Introductionmentioning

confidence: 99%

Examination of small molecule losses in 5‐methylpyranopelargonidin MS/MS CID spectra by DFT calculations

2014

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Pyranoanthocyanins are formed during food treatment and maturation (e.g. wine, juices), and they can be considered a natural alternative to artificial food colorants. Tandem mass spectrometry (MS/MS) is perhaps the most important technique in analysis of anthocyanin dyes. Knowledge of fragmentation pattern is a key aspect of their successful structural characterization. Polyphenolic compounds are known to lose small molecules during collision-induced dissociation (CID) in MS/MS experiments. However, the specific positions where such losses occur preferentially are unknown. The aim of this communication is to investigate the energetically most preferred places for H2 O and CO losses during the fragmentation of 5-methylpyranopelargonidin molecule by the means of computational chemistry (employing density functional theory) combined with CID MS/MS experiments and infrared multiphoton dissociation spectroscopy. Mechanisms responsible for the fragmentations were investigated, and optimal geometries and transition states were obtained. Cleavage of water as well as carbon monoxide occurs preferentially from the C-ring of flavonoid skeleton. In the most stable structure of 5-methylpyranopelargonidin, B-ring was found to be tilted with respect to the rest of the molecule. Planarization effort of the parent molecule contributes both to its decarbonylation and dehydration.

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“…[12] The resonance model has been extensively employed in these systems, for instance, to explain why imidazole is a very much stronger base than thiazole or oxazole, and even ties introduced by amino and nitro substituents, respectively. This electron-density analysis is interesting for at least two reasons: (i) because previous QTAIM studies on diverse heterocycles have provided evidence that the resonance model displays significant shortcomings for describing electron-density evolutions along simple chemical reactions; [19][20][21] and (ii) although azoles are relatively common organic reagents, their electron density has not been the subject of modern electron-density studies. C2 is the most favored site for hydridation in all 1,3azoles, which always results in loss of ring planarity and reduced electron delocalization in the ring.…”

Section: Introductionmentioning

confidence: 99%

An Electron‐Density‐Based Study on the Ionic Reactivity of 1,3‐Azoles

et al. 2012

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Basic processes for the ionic chemistry of 1,3‐azoles (protonation, nitration, hydride addition, and deprotonation) have been studied by analyzing B3LYP/6‐311++G(2d,2p) 6d electron densities using the Quantum Theory of Atoms in Molecules (QTAIM) and delocalization indices in the gas phase and in aqueous solution modeled with the Polarizable Continuum Model (PCM) method. The most stable protonation site is N3 in all cases, and this takes place without a significant change in electron delocalization, whereas C5 is the preferred site for electrophilic substitution. Activating and deactivating effects on the carbon atoms of the imidazole ring were tested by analyzing the variation of atomic properties introduced by amino and nitro substituents, respectively. The largest activation was observed for C5 in 4‐aminoimidazole. C2 is the most favored site for hydridation in all 1,3‐azoles, which always results in loss of ring planarity and reduced electron delocalization in the ring. PCM calculations allow the experimentally observed preferred deprotonation C‐site in water for these compounds to be modeled and reproduced. In all anions, QTAIM charges do not keep in line with the resonance forms; whereas QTAIM describes deprotonated carbon atoms as positive or nearly neutral in the gas phase, they should display negative charge according to the resonance model.

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Conformational and Substitution Effects on the Electron Distribution in a Series of Anthocyanidins

Cited by 21 publications

References 40 publications

Complexation of common metal cations by cyanins: Binding affinity and molecular structure

Complexation of common metal cations by cyanins: Binding affinity and molecular structure

Examination of small molecule losses in 5‐methylpyranopelargonidin MS/MS CID spectra by DFT calculations

An Electron‐Density‐Based Study on the Ionic Reactivity of 1,3‐Azoles

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