Correlated Study of Linear Optical Absorption in Lower Symmetry Coronene Derivatives.

The electronic and optical properties of four different coronene derivatives with lower symmetry, namely, benzo[a]coronene (C$_{28}$H$_{14}$), naphtho[2,3a]coronene (C$_{32}$H$_{16}$), anthra[2,3a]coronene (C$_{36}$H$_{18}$) and naphtho[8,1,2abc]coronene (C$_{30}$H$_{14}$) were investigated. For the purpose, we performed electron-correlated calculations using screened and standard parameters in the $\pi$-electron Pariser-Parr-Pople (PPP) Hamiltonian, and the correlation effects were included, both for ground and excited states, using MRSDCI methodology. The PPP model Hamiltonian includes long range Coulomb interactions which increases the accuracy of our calculations. The results of our calculations predict that with the increasing sizes of the coronene derivatives, optical spectra are red shifted as well as the optical gaps decrease. In each spectrum, the first peak represents the optical gap which is moderately intense, while the more intense peaks appear at higher energies. Our computed spectra are in good agreement with the available experimental data.