HOMA Index Establishes Similarity to a Reference Molecule

Area of Science:

• Computational Chemistry
• Theoretical Chemistry
• Organic Chemistry

Background:

• Aromaticity is a key concept in chemistry, crucial for understanding molecular stability and reactivity.
• Existing methods for assessing aromaticity often rely on electronic properties or complex calculations.
• Geometric similarity to benzene is a proposed indicator of aromatic character.

Purpose of the Study:

• To validate the HOMA index as a reliable measure of geometric similarity to benzene.
• To explore the applicability of HOMA-like indices for assessing other molecular properties beyond aromaticity.
• To demonstrate the HOMA index's utility as a general chemical descriptor.

Main Methods:

• Mathematical analysis of the HOMA index definition against similarity function axioms.
• Application of the HOMA index to assess geometric similarity to benzene and cyclohexane.
• Correlation analysis of HOMA index values with total energy differences and Kekulé counts for hexacene isomers.

Main Results:

• The HOMA index mathematically satisfies similarity function axioms, confirming its suitability for aromaticity assessment.
• HOMA-like indices can quantify other properties, such as the relaxed saturicity of cyclohexane.
• The HOMA index shows strong correlations with energy differences and resonance energy in hexacene isomers, validating its role as a general descriptor.

Conclusions:

• The HOMA index is a robust descriptor for geometric similarity, effectively indicating aromaticity.
• The HOMA index's utility extends beyond aromaticity, enabling the evaluation of diverse molecular properties.
• The HOMA index serves as a versatile and general chemical descriptor for various molecular structures, including rings, chains, and complex molecules.