Heteroatom Incorporation Effect in σ- and π-Electron Systems: The sEDA(II) and pEDA(II) Descriptors

Mazurek, Andrzej; Dobrowolski, Jan Cz.

doi:10.1021/jo202542e

Cited by 36 publications

(46 citation statements)

References 72 publications

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“…The perfect linearity of correlation between the sEDA descriptors constructed for benzenes and pyridines confirms our previous findings that the effect on σ‐electron system of the substituted ring expresses the substituent group electronegativity and is limited to the closest surrounding of the ipso C‐atom . In fact for 2‐substituted pyridines, in which a substituent is in ortho‐ position to the N‐atom (which can be treated as σ‐electron withdrawing incorporant of a parent benzene system), both a substituent and the N‐incorporant act together, yet in an additive way (Figure A).…”

Section: Resultssupporting

confidence: 83%

On the nonadditivity of the substituent effect in homo-disubstituted pyridines

Hęclik

Dobrowolski

2016

J. Phys. Org. Chem.

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The substituent effect in mono‐ and disubstituted pyridines was studied by means of the sEDA and pEDA substituent effect descriptors expressing the substituent effect on the σ‐ and π‐electron systems of the ring, respectively. The sEDA descriptors calculated for mono‐ or disubstituted pyridines can be presented as perfectly linear functions of either benzene or monosubstituted pyridine sEDA descriptors, respectively. For the pEDA descriptors, there are substantial deviations from linearity observed for both mono‐ and disubstituted systems. For the disubstituted systems, the nonadditivity of the pEDA descriptors is strongly pronounced for the substituents in the ortho‐ and para‐positions to each other while it is only weak for the meta‐located groups. For both mono‐ and disubstituted systems, there are correlations between charge at the nitrogen lone electron pair and the σ‐ and π‐electron withdrawing and donating properties of the substituent. In general, the electron charge increases with the increase of the σ‐electron donating ability but decreases with the increase of π‐electron donating ability of substituents. Again, the effects are more significant for substituents in the ortho‐ and para‐positions than in the meta‐position. The influence of the π‐electron properties of the substituent on the lone pair, belonging to σ‐electron system of pyridines, shows the presence of hyperconjugation effects in the substituted pyridines. The hyperconjugation can be also clearly observed in cross‐dependencies of the sEDA and pEDA descriptors.

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Section: Resultssupporting

confidence: 83%

On the nonadditivity of the substituent effect in homo-disubstituted pyridines

Hęclik

Dobrowolski

2016

J. Phys. Org. Chem.

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“…Similar bond length alternation was found in each of the other optimized MC 4 H 4 structures, suggesting the possible antiaromatic nature of these species (as expected from the four π electrons present in the planar molecular ring). This is also supported by positive NICS(1) zz indices (15.6 ppm for BeC 4 H 4 and 5.2 ppm for MgC 4 H 4 ; calculated at the B3LYP/aug‐cc‐pVDZ level by Mazurek and Dobrowolski). The reduced NICS(1) zz values from BeC 4 H 4 to MgC 4 H 4 coincide with the slightly more balanced C−C and C=C bond lengths in MgC 4 H 4 than in BeC 4 H 4 [a difference of 0.166 Å for BeC 4 H 4 and 0.156 Å for MgC 4 H 4 at CCSD(T)/cc‐pVTZ].…”

Section: Resultsmentioning

confidence: 99%

Prediction and Characterization of Alkaline‐Earth (M=Be, Mg, Ca, Sr, and Ba) Metallacyclopentadienes and Relevant Derivatives

2017

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Alkaline‐earth metallacyclopentadienes are an active area of research in synthetic chemistry, notable for their roles as precursors of key cyclopentadiene derivatives. However, experimental characterization is limited due to their challenging synthesis and subsequent isolation. Herein, we report systematic theoretical studies of MC4H4 (M=Be, Mg, Ca, Sr, Ba) rings and experimentally relevant complexes. Benchmarking against CCSD(T) and experiment shows reasonable performance for the B3LYP, BP86, and M06‐2X density functionals in predicting the equilibrium geometries, thermochemistry, and vibrational spectra of these species. NICS indices and extra cyclic resonance energies confirm that the compounds in question possess antiaromatic character. For both the bare MC4H4 rings and larger complexes, the Be‐containing compounds were found to be the most strongly bound species. Such viability is explained via ring strain, electron densities, natural bond orders, and orbital analyses. Given that the second least viable Mg complex has been reported in recent experiments, synthesis and characterization of the other group IIA analogs are anticipated.

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“…The same aromaticity order was previously observed for various forms of thiomaltols. Such behaviour is expected because the replacement of oxygen by sulfur or selenium significantly changes the sigma‐electronic structure of molecular systems, whereas the pi‐electronic structure is not significantly changed . Thus, it is reasonable that different forms (anion, neutral molecule and cation) of studied compounds have an identical order of relative aromaticity for maltol as for its sulfur and selenium derivatives.…”

Section: Discussionmentioning

confidence: 99%

Molecular properties of selenomaltols: new interesting ligands for bioactive metal complexes

Tejchman

Proniewicz

Zborowski

2015

J of Physical Organic Chem

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Properties of numerous selenium derivatives of maltol (3‐hydroxy‐2‐methyl‐4H‐pyran‐4‐one), which is an important ligand in medicinal chemistry, were studied. Selenium derivatives were obtained using consecutive in silico replacements of maltol oxygen atoms, which produced three mono‐substituted, three di‐substituted and one tri‐substituted derivatives. The geometry optimisations for these compounds in neutral, anionic and cationic forms were performed at the B1LYP/6‐311++G** level of theory. The aromatic properties of the considered selenium compounds were studied in their heterocyclic rings using several indices of aromaticity: harmonic oscillator model of aromaticity, nucleus independent chemical shift(0), nucleus independent chemical shift(1), aromatic stabilisation energy, H index, para delocalisation index and multicentre index. The methods cover all of the main types of aromaticity indices: geometric, magnetic, energetic and electronic. The calculated data show the identical aromaticity order (cation > neutral molecule > anion) for maltol and its thio and seleno derivatives. The predicted aromaticity levels of selenomaltols were compared with the previously studied maltol and various thiomaltols. Copyright © 2015 John Wiley & Sons, Ltd.

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Heteroatom Incorporation Effect in σ- and π-Electron Systems: The sEDA(II) and pEDA(II) Descriptors

Cited by 36 publications

References 72 publications

On the nonadditivity of the substituent effect in homo-disubstituted pyridines

On the nonadditivity of the substituent effect in homo-disubstituted pyridines

Prediction and Characterization of Alkaline‐Earth (M=Be, Mg, Ca, Sr, and Ba) Metallacyclopentadienes and Relevant Derivatives

Molecular properties of selenomaltols: new interesting ligands for bioactive metal complexes

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