Electron delocalization and aromaticity in linear polyacenes: atoms in molecules multicenter delocalization index

Area of Science:

• Quantum Chemistry
• Organic Chemistry
• Materials Science

Background:

• Linear polyacenes are a class of organic molecules with potential applications in organic electronics.
• Understanding their electronic properties, particularly aromaticity, is crucial for predicting their behavior.
• Existing methods for assessing aromaticity have limitations in accurately describing electron delocalization in these systems.

Purpose of the Study:

• To investigate molecular aromaticity in linear polyacenes.
• To introduce and apply a novel Atoms in Molecules based six center index (SCI-AIM) for quantifying electron delocalization.
• To compare the SCI-AIM approach with other established methods like Mulliken-like analysis and the PDI index.

Main Methods:

• Application of the six center index (SCI-AIM), an Atoms in Molecules based method.
• Calculation of SCI-AIM values for a series of linear polyacenes.
• Comparative analysis of SCI-AIM results against Mulliken-like and PDI indices.

Main Results:

• SCI-AIM values demonstrate a clear trend of decreasing aromaticity from the outer to the inner rings within the linear polyacene series.
• The study provides a quantitative measure of electron delocalization specific to the ring systems.
• The SCI-AIM method offers a valuable alternative for aromaticity assessment.

Conclusions:

• Molecular aromaticity in linear polyacenes is not uniform across the molecule, with inner rings exhibiting reduced electron delocalization.
• The SCI-AIM provides a robust and insightful method for evaluating aromaticity and electron delocalization in conjugated systems.
• This work contributes to a deeper understanding of structure-property relationships in polyacene chemistry.