Theoretical insights into “D-A-D” type Aza-BODIPY dyes for enhanced photothermal performance

Developing photothermal agents (PTAs) with both strong near-infrared absorption and high photothermal conversion efficiency is essential for enhancing the efficacy of cancer photothermal therapy (PTT). In this study, theoretical methods are used to systematically investigate the effects of molecular conformation, excited-state behavior, and intermolecular interactions of “D-A-D” type Aza-BODIPY dyes (BDP1, BDP2, BDP3, BDP4) on their near-infrared absorption and photothermal properties. Geometric structure, excited-state data, and frontier molecular orbital analysis reveal that enhancing the electron-donating ability of the donor group at the 1,7-positions of Aza-BODIPY can narrow the HOMO-LUMO gap, driving a redshift in the absorption spectrum. Simultaneously, strong electron-donating groups can induce a photoinduced electron transfer process, facilitating non-radiative decay. Molecular dynamics simulations further reveal the formation of dimer head-to-tail stacking structures for BDP1, BDP2, BDP3, and BDP4, with slip angles indicating the potential for CT-coupled J-aggregation formation. Additionally, enhanced electron-donating ability at the 1,7-positions strengthens π-π stacking, promoting the conversion of non-radiative heat energy. This study elucidates the influence of D-A-D type Aza-BODIPY dyes on photothermal performance and provides a theoretical basis for the design of efficient near-infrared photothermal agents.