A New Set of Aromaticity Descriptors Based on the Electron Density Employing the Distributed Multipole Analysis (DMA)
Matheus Máximo-Canadas1, Roberta Siqueira Soldaini Oliveira1, Marco Aurélio Souza Oliveira1
1Departamento de Química, Instituto Militar de Engenharia (IME), Praça General Tibúrcio, 80, Rio de Janeiro, RJ 22290-270, Brazil.
ACS Omega
|April 21, 2025
Summary
Researchers developed new aromaticity descriptors using distributed multipole analysis (DMA) to quantify cyclic electron delocalization. These novel indices, based on electric multipole moments, show promise in predicting aromaticity trends across various chemical systems.
Area of Science:
- Quantum Chemistry
- Computational Chemistry
- Organic Chemistry
Background:
- Aromaticity is a key chemical concept, crucial for stability and reactivity, yet difficult to quantify due to its unmeasurable nature.
- Existing descriptors for aromaticity often struggle with diverse molecular structures and require complex calculations.
- Cyclic electron delocalization is fundamental to aromaticity, necessitating methods that capture this electronic feature.
Purpose of the Study:
- To introduce six novel aromaticity descriptors derived from Stone's distributed multipole analysis (DMA).
- To provide a computational protocol for calculating these new descriptors using readily available software.
- To evaluate the performance of these descriptors against established benchmarks for aromaticity.
Main Methods:
- Utilized Stone's distributed multipole analysis (DMA) to calculate electric multipole moments, specifically focusing on the quadrupole tensor components.
- Developed a Python script to compute the proposed aromaticity descriptors from DMA outputs.
- Assessed descriptor performance using the Girona benchmark, comprising 12 diverse chemical tests including substituted benzenes, heteroatomic species, and Clar systems.
Main Results:
- The six new aromaticity descriptors, particularly when normalized against benzene values, demonstrated consistent performance in predicting aromaticity trends.
- Normalized descriptors correctly predicted aromaticity trends in 65% of test cases and partially in 22%, with failures mainly linked to molecular symmetry or sigma electron contamination.
- The DMA-based approach offers a practical method for quantifying electron delocalization, a core aspect of aromaticity.
Conclusions:
- The proposed DMA-based aromaticity descriptors provide a valuable new tool for quantifying this complex chemical concept.
- Normalization against benzene significantly improves the reliability and consistency of these novel descriptors.
- Further development may address limitations related to molecular symmetry and sigma electron interference for broader applicability.
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