Study on the mechanism of oxygen atom-related non-covalent interactions on the structure of non-fused ring acceptor molecules and their optoelectronic properties

Abstract Non-covalent interactions play a crucial role in regulating the molecular conformation and optoelectronic properties of the acceptor. In this paper, hydroxyl groups of different positions and numbers are inserted on the original non-fused ring acceptor molecule W0. Thus, eight novel molecules were designed. Density functional theory (DFT) and time-dependent DFT (TD-DFT) are used to investigate the mechanisms of non-covalent interactions between S…O on the molecular conformation, electronic structure and its optoelectronic properties. The existence of intramolecular S…O non-covalent interactions was demonstrated by the Atoms-In-Molecules topological analysis and RDG isosurface visualization. The study of the molecular conformational planarity revealed that the introduction of unilateral groups can optimize the homolateral planarity. As the number of hydroxyl insertions increases, the twisting of the two thiophene units within the central core intensifies. This also leads to an impact on the internal planarity of the central core. The electrostatic potential (ESP) analysis showed that the asymmetric hydroxyl modification increased the dipole moment and may be more beneficial for electron transfer. The larger the dipole moment, the more negative the ESP. Theoretical results show that the introduction of hydroxyl groups is significantly superior in terms of light absorption, dipole moment and exciton binding energy as well as excitation energy. As the number of hydroxyl groups increases, they show more potential in increasing the excitation energy and light absorption and decreasing the exciton binding energy. This study provides new insights into the design and development of high-performance non-fused ring acceptors.