Relation between the Substituent Effect and Aromaticity

Krygowski, Tadeusz M.; Ejsmont, Krzysztof; Stępień, Beata T.; Cyrański, Michał K.; Poater, Jordi; Solà, Miquel

doi:10.1021/jo0492113

Cited by 190 publications

(188 citation statements)

References 60 publications

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“…In accordance with the earlier studies [46] in the case of phenol derivatives, HOMA and NICSs present a very low variability and no clear dependences on SE characteristics are observed. Nevertheless, the ranges of the variability of HOMA and NICS aromaticity characteristics are dramatically greater for para-substituted phenolates than for phenols (∼10 and 2 times, respectively).…”

Section: Substituent Effects On Transmitting Moiety Propertiessupporting

confidence: 91%

How OH and O– groups affect electronic structure of meta-substituted and para-substituted phenols and phenolates

2017

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An application of two independent quantum chemistry-based concepts, a substituent effect stabilization energy (SESE) and a charge of the substituent active region (cSAR), for describing substituent effects allows to investigate a nature of mutual interactions between substituents. The B3LYP/6-311++G(d,p) method is employed to examine changes in properties of a reaction center Y (Y = OH or O -groups) and a transmitting moiety (the benzene ring) due to substituent effects in a series of meta-X-substituted and para-X-substituted phenol and phenolate derivatives (X = NMe 2 , NH 2 , OH, OMe, CH 3 , H, F, Cl, CF 3 , CN, CHO, COCl, COMe, CONH 2 , COOH, NO 2 , NO). HOMA, NICS(1) and pEDA parameters are used to characterize π-electron delocalization of the transmitting moiety. Relations between cSAR(X) and σ constants show almost identical sensitivity of the substituent effect in meta-substituted phenol and phenolate derivatives, whereas in para-substituted analogs, different kinds of intramolecular interactions have been revealed. Due to electron attractive property of OH group in meta position, dependences of cSAR(X) on SESE show a dramatically different picture of interaction in meta-substituted phenols as compared to that found for all other series studied. Moreover, this group affects in a different way the electronattracting and electron-donating substituents in meta position. A clear substituent effect on π-electron delocalization of the benzene ring is observed only in para-substituted phenolate derivatives. The application of cSAR(X) parameter allows to estimate a difference between its value for a particular substituent in meta and para derivatives. In some cases, this difference amounts up to ∼53% of the range of cSAR(X) variability.Keywords substituent effects . electronic structure . molecular modeling . substituent effect stabilization energy . charge of the substituent active region

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Section: Substituent Effects On Transmitting Moiety Propertiessupporting

confidence: 91%

How OH and O– groups affect electronic structure of meta-substituted and para-substituted phenols and phenolates

2017

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“…In particular, changes of PDI when going from benzene to substituted benzene derivatives are small and correlated with Hammett substituent constants. 142 The same behaviour was observed for the complexation of a lithium cation to a series of PAHs. 159 Substituent effects were also studied in 4-substituted-1,2-benzoquinones.…”

Section: Substituent Effects On Aromaticitysupporting

confidence: 57%

Quantifying aromaticity with electron delocalisation measures

et al. 2015

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Aromaticity cannot be measured directly by any physical or chemical experiment because it is not a well-defined magnitude. Its quantification is done indirectly from the measure of different properties that are usually found in aromatic compounds such as bond length equalisation, energetic stabilisation, and particular magnetic behaviour associated with induced ring currents. These properties have been used to set up the myriad of structural-, energetic-and magnetic-based indices of aromaticity known to date. Cyclic delocalisation of mobile electrons in two or three dimensions is probably one of the key aspects that characterise aromatic compounds. However, it has not been until the last decade that electron delocalisation measures have been widely employed to quantify aromaticity. Some of these new indicators of aromaticity such as the PDI, FLU, ING, and INB were defined in our group. In this paper, we review the different existent descriptors of aromaticity that are based on electron delocalisation properties, we compare their performance with indices based on other properties, and we summarise a number of applications of electronic-based indices for the analysis of aromaticity in interesting chemical problems.2

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“…The obtained results for the retrieved data set ( Figure 6) confirm this suggestion, showing the range of HOMA values from 0.826 and in a more regular way between 0.88 and 1.00. A relatively small decrease in the aromatic character of the phenyl ring as an effect of the substituent is in line with more detailed studies based on QM modeling of this problem [42,43]. The obtained results for the retrieved data set ( Figure 6) confirm this suggestion, showing the range of HOMA values from 0.826 and in a more regular way between 0.88 and 1.00.…”

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confidence: 86%

“…The obtained results for the retrieved data set ( Figure 6) confirm this suggestion, showing the range of HOMA values from 0.826 and in a more regular way between 0.88 and 1.00. A relatively small decrease in the aromatic character of the phenyl ring as an effect of the substituent is in line with more detailed studies based on QM modeling of this problem [42,43]. It is important to note that histograms of the data sets for para-substituted nitrobenzene derivatives and measurements with R ≤ 0.075 or 0.1 are characterized by similar shapes and statistical parameters as shown above; only a slightly greater range of variability of the studied parameters and their esds were observed.…”

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confidence: 82%

Effect of Intra- and Intermolecular Interactions on the Properties of para-Substituted Nitrobenzene Derivatives

et al. 2016

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Abstract:To study the influence of intra-and intermolecular interactions on properties of the nitro group in para-substituted nitrobenzene derivatives, two sources of data were used: (i) Cambridge Structural Database and (ii) quantum chemistry modeling. In the latter case, "pure" intramolecular interactions were simulated by gradual rotation of the nitro group in para-nitroaniline, whereas H-bond formation at the amino group allowed the intermolecular interactions to be accounted for. BLYP functional with dispersion correction and TZ2P basis set (ADF program) were used to perform all calculations. It was found that properties of the nitro group dramatically depend on both its orientation with respect to the benzene ring as well as on the substituent in the para-position. The nitro group lies in the plane of the benzene ring for only a small number of molecules, whereas the mean value of the twist angle is 7.3 deg, mostly due to intermolecular interactions in the crystals. This distortion from planarity and the nature of para-substituent influence the aromaticity of the ring (described by HOMA index) and properties of the nitro group due to electronic effects. The results obtained by QM calculations fully coincide with observations found for the data set of crystal structures.

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Relation between the Substituent Effect and Aromaticity

Cited by 190 publications

References 60 publications

How OH and O– groups affect electronic structure of meta-substituted and para-substituted phenols and phenolates

How OH and O– groups affect electronic structure of meta-substituted and para-substituted phenols and phenolates

Quantifying aromaticity with electron delocalisation measures

Effect of Intra- and Intermolecular Interactions on the Properties of para-Substituted Nitrobenzene Derivatives

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