Computational study of chiral molecules with high intrinsic hyperpolarizabilities

Abstract

We have investigated the electronic transition, chiroptical properties, and the second-order nonlinear optical (NLO) properties of eight novel chiral diborate compounds and elucidated structure–property relationships from the micromechanism. These compounds show calculated first hyperpolarizabilities (β) ranging from 2738.52 to 83976.45 × 10−33 esu, which means that subtle structural modifications can substantially enhance the first hyperpolarizability. The cooperativity of intramolecular charge transfer and an effective way to enhance the NLO response were also systemically investigated. The linear correlation between the first hyperpolarizability and the inverse of the electronic transition energy suggests that the electronic transition energy plays a key role in determining the NLO response. These compounds have the potential to be excellent second-order NLO materials from the standpoint of the large β values, high transparency and the intrinsic non-centrosymmetry. The electronic transition and chiroptical properties have been assigned and analysed. The main UV–visible absorption features are best described as π → π* transitions. Moreover, the effects of different functionals and basis sets on the first hyperpolarizability were investigated.