Theoretical study on the nonlinear optical properties of donor/acceptor-functionalized trigonal dehydrobenzoannulenes

The first hyperpolarizabilities β and ultraviolet spectra of two-dimensional charge transfer (2DCT) donor/acceptor-functionalized trigonal dehydrobenzoannulenes (compounds 2–7) have been calculated by using ab initio quantum chemistry methods. It is found that these multiple substituted chromophores possess large β values, where both diagonal and off-diagonal terms play important roles in β. This is different from the typical one-dimensional charge transfer (1DCT) compounds, where β is dominated by the diagonal terms. It is worth noting that a good nonlinearity-transparency trade-off is achieved for compounds 2–7 which exhibit larger β values coupled with enhanced transparency in the visible region. Moreover, the contributions of dipolar components to β are larger than that of octupolar components for compounds 2–7.