Tuning optical properties of conjugated molecules by Lewis acids: Insights from electronic structure modeling and machine learning

The change in optical properties of an organic semiconductors upon forming adducts with inexpensive small molecules is attractive in organic electronics. We focus on the adducts of conjugated molecules and Lewis acids (CM-LA), formed by the partial electron transfer from a CM containing a Lewis basic site to an LA such as BF3 and B(C6F5)3. The resulting adducts showed intriguing optoelectronic properties, including a red-shift in optical transitions and an increase in charge carrier density compared to the parent conjugated molecules. In this work, we combine electronic structure modelling and machine learning (ML) to quantify, analyze and predict the electron transfers and red-shifts of the adducts from chemical structures. For ML model, we utilize DFT-calculated electron transfers and redshifts and molecular descriptors readily calculated from molecular structures. Our work can help researchers in other fields in predicting fundamental properties from molecular structures.