Elucidating Aggregation Pathways in the Donor-Acceptor Type Molecules p-DTS(FBTTh

Area of Science:

• Materials Science
• Physical Chemistry
• Computational Chemistry

Background:

• Donor-acceptor molecules are crucial for organic electronics.
• Understanding molecular aggregation is key to controlling material properties.
• The aggregation behavior of p-DTS(FBTTh2)2 (T1) and p-SIDT(FBTTh2)2 (H1) differs significantly.

Purpose of the Study:

• To investigate and explain the differing aggregation behaviors of T1 and H1 in MTHF solutions.
• To elucidate the molecular factors governing aggregation in these donor-acceptor systems.

Main Methods:

• Optical spectroscopy was used to observe aggregation in solution and thin films.
• Free energy molecular dynamics (MD) simulations were performed.
• Force fields were derived from quantum-mechanical density functional theory calculations.

Main Results:

• T1 aggregates in MTHF solution, while H1 does not.
• MD simulations accurately reproduced the experimental observations.
• Molecular symmetry, not side-chain length, was identified as the critical factor.
• T1's symmetry allows for donor unit separation in aggregates; H1's symmetry does not.
• H1 aggregation requires desolvation, leading to kinetic hindrance.

Conclusions:

• Molecular symmetry is a primary determinant of aggregation behavior in these donor-acceptor molecules.
• The differing aggregation tendencies of T1 and H1 are explained by steric constraints and solvation effects.
• Computational methods provide accurate insights into molecular aggregation phenomena.