Interplay between diradical character, aromaticity and conductance in oligothiophenes

Area of Science:

• Organic Electronics
• Materials Science
• Computational Chemistry

Background:

• Oligothiophenes exhibit tunable electronic properties based on their structure.
• Understanding the interplay between diradical character, aromaticity, and conductance is crucial for designing organic electronic materials.

Purpose of the Study:

• To elucidate the fundamental relationships within the diradical character-aromaticity-conductance triangle in oligothiophenes.
• To investigate the influence of electronic ground-state structure on these relationships.
• To explore the impact of local and global aromaticity on charge transport.

Main Methods:

• Quantum chemical calculations to determine electronic ground-state properties.
• Calculation of singlet-triplet adiabatic energy gaps and diradical character (y0) using Yamaguchi's approach.
• Analysis of multicenter indices, delocalization indices, and AVmin for aromaticity and charge transport.

Main Results:

• All studied oligomers possess a singlet ground state; only 13 showed non-zero diradical character.
• Diradical character and aromaticity are intrinsically linked, with modulation of one affecting the other.
• Conductance is enhanced by higher diradical character but attenuated by molecular length and influenced by local aromaticity disruptions.

Conclusions:

• The study extends the traditional diradical-aromaticity-conductance framework by including electronic ground-state structure as a fourth vertex.
• Distinguishing between local and global aromaticity-conductance relationships provides deeper insights into charge transport.
• The findings offer a comprehensive understanding of the electronic origins of molecular properties and their impact on charge transport in organic materials.