Sigma- and pi- electron structure of aza-azoles

Krygowski, Tadeusz M.; Ozimiński, Wojciech P.; Ramsden, Christopher A.

doi:10.1007/s00894-010-0844-z

Cited by 21 publications

(13 citation statements)

References 15 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Correlation between pEDA and NICS has previously been recognised in a study of aza-azoles. 52 The rings 8e9 are slightly p rich and the calculated pEDA values (Table 1) are consistent with rings associated with 6.3AE0.1 p electrons. This contrasts with our earlier study of six-membered isomers, 2 which are much more electron rich (pEDA 7.0AE0.2), and accordingly display lower magnetic aromaticity as measured by the NICS index.…”

Section: Resultssupporting

confidence: 77%

A DFT and ab initio study of conjugated and semi-conjugated mesoionic rings and their covalent isomers

Ozimiński

Ramsden

2015

Tetrahedron

Self Cite

View full text Add to dashboard Cite

Section: Resultssupporting

confidence: 77%

A DFT and ab initio study of conjugated and semi-conjugated mesoionic rings and their covalent isomers

Ozimiński

Ramsden

2015

Tetrahedron

Self Cite

View full text Add to dashboard Cite

“…Using quantum chemical approaches, many efforts have been made to model the substituent effect . Substituent effects are responsible for small perturbations on the molecular electron density distribution, which can be measured by means of correlating them with the computed quantities of total energy, atomic charges, and electrostatic potentials resulting from ab initio quantum chemical or semiempirical methods . Further, several experimental studies have utilized Y‐G‐X type systems to understand the substituent effect transmission ability of various spacer moieties using geometrical variables, ionization techniques, and NMR chemical shifts etc …”

Section: Introductionmentioning

confidence: 99%

Substituent Effect Transmission Power of Alkyl, Alkenyl, Alkynyl, Phenyl, Thiophenyl, and Polyacene Spacers

2019

View full text Add to dashboard Cite

The transmission of substituent effect through a variety of spacers, that is to say, alkyl, alkenyl, alkynyl, phenyl, thiophenyl, and polyacene has been studied by modeling Y‐G‐X type molecular systems (Y: reaction center; G: spacer moiety; X: substituent) using B3LYP/6‐31G(d,p) density functional theory calculations. The reaction center is always kept as a C=C double bond and the molecular electrostatic potential (MESP) minimum (Vmin) observed for this bond showed subtle variation with respect to the changes in the spacer unit and the nature of substituent. Strong linear correlations are observed between Hammett substituent constants (σI and σp) and Vmin, which recommend the aptness of Vmin as an electronic descriptor to quantify the substituent effect. Since Vmin offers an alternative measure of substituent effect, the correlation between Vmin and σp has been used for assessing the transmission of substituent effect through a variety of spacer moieties. The highest transmission coefficient (γ) is always observed for smaller spacer length. Among all the spacers, alkenyl showed the highest and alkyl showed the lowest transmission power. The study recommends the use of short chains of C=C double, C≡C triple or a combination of both as spacers for the effective transmission of substituent effect to the reaction center.

show abstract

“…One more quantitative characteristic based on quantum chemistry modeling is charge of the substituent active region, with an acronym cSAR(X), which is a sum of atomic charges of all atoms of the substituent X and the carbon atom to which the X is attached. Recently, it has been shown that cSAR(X) values correlate well with SCs . Very important feature of cSAR(X) characteristic is its independence of the method of the atomic charge assessment; the obtained by different methods quantities exhibits good mutual correlations …”

Section: Introductionmentioning

confidence: 99%

Olefinic vs aromatic way of substituent effects: The case of 3- and 4-substituted cyclohexa-1,3-dienamine derivatives

2017

Self Cite

View full text Add to dashboard Cite

Quantum chemical modeling was used to confront substituent effects in olefinic systems with an analogous situation in benzene. The B3LYP/6-311++G(d,p) method was applied to examine electron-donating properties of the amino group in a series of 3-(meta-like) and 4-(para-like) X-substituted cyclohexa-1,3-dienamines (X = NMe 2 , NH 2 , OH, OMe, Me, H, F, Cl, CF 3 , CN, CHO, COMe, CONH 2 , COOH, NO 2 , NO). As in the case of substituted anilines (PCCP, 2016, 18, 11711), the substituent properties were described by σ, charge of the substituent active region(X), and substituent effect stabilization energy descriptors; the amino group was characterized by structural and electronic parameters, whereas a transmitting moiety-by aromaticity index harmonic oscillator model of aromaticity. All applied substituent properties parameters were found to be mutually interrelated, with much better correlations for the para-derivatives than the meta-derivatives.Electron-donating ability of the amino group is stronger affected (circa 1.4 times) by substituent acting from position 4 in cyclohexa-1,3-dienamines than in aniline derivatives. It was also numerically confirmed that the reverse substituent effect acting to para-position is stronger (circa 1.14 times) in olefinic systems than in aromatic ones. Moreover, for 1-4 interactions, an increase of the electron-attracting power of the substituent increases π-electron delocalization in the olefinic series, whereas decreases it in the aromatic ones.

show abstract

Sigma- and pi- electron structure of aza-azoles

Cited by 21 publications

References 15 publications

A DFT and ab initio study of conjugated and semi-conjugated mesoionic rings and their covalent isomers

A DFT and ab initio study of conjugated and semi-conjugated mesoionic rings and their covalent isomers

Substituent Effect Transmission Power of Alkyl, Alkenyl, Alkynyl, Phenyl, Thiophenyl, and Polyacene Spacers

Olefinic vs aromatic way of substituent effects: The case of 3- and 4-substituted cyclohexa-1,3-dienamine derivatives

Contact Info

Product

Resources

About