Computational study on second-order nonlinear optical (NLO) properties of a novel class of two-dimensional Λ- and W-shaped sandwich metallocarborane-containing chromophores

We systematically investigate the linear optical properties and the static second-order nonlinear optical (NLO) properties on a series of two-dimensional (2D) D-π-A-π-D/A-π-D-π-A sandwich metallocarborane-containing molecules with density functional theory (DFT). It can be found that the substitution effect has an influence on the electronic absorption and NLO responses of the 2D molecules. For example, the βvecβvec value is sensitive to the substitution from amino (–NH2) to nitryl (–NO2); the angle between the two A–D branches significantly affects the dipole moment and βvecβvec value. In addition, time-dependent DFT calculations and the analysis of major molecular orbitals predict that the sandwich metallocarborane acts as an electron donor better than electron acceptor. Furthermore, the two strong synchronized charge transfer (CT) coming from the two branches and p–π (B2p–C≡C) conjugation contributes to the second-order polarizabilities in our studied systems.