Molecular structure and electronic properties of substituted tetrabenzocoronenes: DFT and TD‐DFT investigations

Abstract

Abstract1,2:3,4:7,8:9,10‐Tetrabenzocoronene (TBC) is a highly π‐conjugated polycyclic aromatic hydrocarbon (PAH) with an intriguing nonplanar, twisted molecular shape featuring two [4]helicene subunits on the opposite sides of the molecule. In this study, we examined the electronic substituent effects on the molecular properties of a series of TBC derivatives by density functional theory (DFT) and time‐dependent DFT (TD‐DFT) computational analysis at the B3LYP/6‐31G(d) and TD‐B3LYP/6‐311 + G(d,p) levels. The equilibrium geometries for the stable conformers of the TBC derivatives in the ground singlet state (So) and related transition states were optimized to obtain the energy barriers associated with the interconversion among these conformers. Variations of aromatic character for these compounds were evaluated by nucleus‐independent chemical shift (NICS) calculations, while the frontier molecular orbital (FMO) energies and the vertical electronic absorption and emission energies were calculated. The calculated absorption and emission spectra of these TBC derivatives show good correlations with the Hammett substituent constant (σ). Overall, our study has demonstrated that the attachment of electron‐donating/withdrawing substituents to the edges of TBC can exert significant effects on the structural, electronic, and photophysical properties. Understanding of the substitution effects on TBC provides valuable insight for the design and development of novel PAH‐based organic electronic materials and devices.