Correlations between the benzene character of acenes or helicenes and simple molecular descriptors (original) (raw)
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Journal of Molecular Modeling, 2015
There are four types of aromaticity criteria: energetic, electronic, magnetic and geometric. The delocalization, density and degeneracy-based index of aromaticity, D3BIA, is an electronic aromaticity index from QTAIM that is not reference dependent and can be used for aromatic, homoaromatic, sigma aromatic and other aromatic systems with varying ring size containing hetereoatoms or not. We used B3LYP, MP2 and MP3 methods to search for linear relations between well-known aromaticity indices and D3BIA for a series of acenes. We found that the D3BIA versus FLU correlation exceeded 91 % and reasonably good correlations exist between D3BIA and HOMA and between D3BIA and PDI. Previous works have shown that D3BIA can be used for homoaromatic systems and tetrahedrane derivatives (sigma aromaticity), but no previous work has validated D3BIA for benzenoid systems. This is the first time we have shown that D3BIA can be used successfully for benzenoid systems, for example, acenes. This work supports and validates the use of D3BIA in classical aromatic systems.
Results on the Estrada Indices of Benzenoid Hydrocarbons
Polycyclic Aromatic Compounds, 2020
The spectral moments of the edge adjacency matrix and adjacency matrix recently have been successfully employed in quantitative structureproperty relationship and quantitative structure-activity relationship studies of alkanes, alkyl halides, benzyl alcohols,cycloalkanes and benzenoid hydrocarbons. Let G be a molecular graph with n vertices, m edges and G(L) be a line graph. Both graphs G and G(L) can be represented by their adjacency matrixes A and E, respectively. The eigenvalues of G and G(L) are denoted by, k 1 Pk 2 P Á Á Á Pk n and c 1 Pc 2 P Á Á Á Pc n , respectively. The Estrada index A and G(L) are defined as EEðGÞ ¼ P n i¼1 e ki and EEðGðLÞÞ ¼ P n i¼1 e c i : In this paper, we examined both Estrada indices with spectral moments of the edge adjacency matrix and adjacency matrix of benzenoid hydrocarbons. These theoretical conclusions provide practical guiding significance for pharmaceutical engineering, complex network and quantify the degree of folding of long organic molecules.
The extent of unsaturation level in a compound, commonly measured in terms of its number of double bond equivalents (DBEs), reflects the total number of p bonds plus rings and can be calculated if the molecular formula is known. The extent of unsaturation can also be calculated via DBE/C, where C is the number of carbon atoms. For hydrocarbons, if DBE/C is > 0.67, the structure corresponds unequivocally to a condensed aromatic (CA) compound, but this criterion cannot be applied directly to heteroatom containing compounds. A new parameter, the aromaticity index (AI) was recently proposed to solve this problem, and has been applied to establish a region of CA compounds in high resolution mass spectrom-etry (MS) van Krevelen diagrams to characterize natural organic matter (NOM), such as humic acids (HAs). In this study, we report a reformulated AI (rAI) that also considers formulae that accommodate non-aromatic (NA) and non-condensed aromatic (NCA) cyclic carbonyl compounds. We also propose a correction for AI with respect to N and P containing formulae and show an application of the rAI index for the analysis and data treatment of a certified reference material (CRM) of NOM.
Journal of Mathematical Chemistry, 2007
The distance-based topological indices viz Wiener (W)-, Szeged (Sz)-, Padmakar-Ivan (PI)- and Sadhana (Sd)-indices have been used for estimating aromatic stabilities as well as % benzene character of polyacenes and helicenes. Excellent models are obtained in combined set and there was no need to split the data set into polyacenes and helicenes. The newly introduced Sd index was found the best index among all the four indices used. In bi-parametric modeling with the combination of the Sd index with the PI index yielded excellent results. The results are discussed critically on the basis of variety of statistical parameters.
Generalized Polansky Index as an aromaticity measure in polycyclic aromatic hydrocarbons
2006
In this work, the ideas of molecular quantum similarity are used to generalize the Polansky similarity index. The newly developed index gauges the aromaticity of individual benzenoid rings in polyaromatic hydrocarbons by its similarity to benzene beyond the scope of simple Hückel theory on which it was originally based. The reported generalization allows the new index to be calculated at a realistic contemporary ab initio level of theory, opening the possibility of its use as a new measure of aromaticity. As will be shown, the new index correlates very well not only with the original Polansky index but also with the Generalized Population Analysis based multicenter index.
Correlations for the acute toxicity of multiple nitrogen substituted aromatic molecules
Ecotoxicology and Environmental Safety, 1985
Twenty-nine compounds, including amino and nitro derivatives of aromatic hydrocarbons as well as azaarenes and indole analogs, were assayed. The biological activity was monitored as population growth to axenic cultures of the ciliate Tetrahymena pyrijimnis. Structure-activity relationships were examined by linear regression analysis of log biological activity (Y) and log 1-octanol/water partition coefficient (X). Partition coefficients were determined by linear regression analysis of the retention time index of HPLC data. Attempts to generate linear predictive correlations for all the test compounds (n = 29; r* = 0.325; P > 0.0013) and groups, subdivided based on the following chemical classes: aromatic hydrocarbons (n = 13; r2 = 0.122; P > 0.2417), azaarenes (n = 9; r* = 0.348; P > 0.0946) and indole analogs (n = 7; r* = 0.743; P > 0.0126), met with little success. Similarly, subdivisions based on the presence of a single (n = 14; r* = 0.514; P > 0.0039) or multiple H-polar groups, i.e., NO?, NH2 (n = 15; r* = 0.195; P > 0.0996), met with little success also. However, if one segregates the compounds which have para oriented H-polar substituents one gets a strong linear predictive correlation (n = 11; r* = 0.889; P > 0.0001). A subdivision of the remaining data set leads to two models (n = 11; r 2 = 0.845; P > 0.0001) and (n = 7; r * = 0.965; P > 0.0001). An examination of the toxicity partitioning product values suggests the three-line predictive correlation model of these data is valid. 0 1985 Academic press. h.
Journal of Molecular Structure-theochem, 2001
Recently a new methodology to identify the carcinogenic activity of polycyclic aromatic hydrocarbons (PAHs) was proposed. This methodology named electronic indices methodology (EIM) is based on the use of local density of states (LDOS) calculations. In this work we perform a comparative study of this methodology with principal component analysis (PCA) and arti®cial neural networks (ANN). All the physicochemical descriptors were calculated from the molecular eigenstates/spectra obtained through the well-known semi-empirical method parametric method 3 (PM3). PCA and ANN results show that EIM descriptors are relevant to identify the carcinogenic activity of methylated and non-methylated PAHs. Also, we show that the combined use of these distinct methodologies can be an ef®cient and powerful tool in the structure±activity studies of PAHs or other organic compounds. We have studied 81 methylated and non-methylated PAHs, and our study shows that with the use of these methods it is possible to predict correctly the PAHs' carcinogenic activity with high accuracy (,80%). q