Effects of isomerism on two-photon absorption of substituted benzenes with two pairs of donor–acceptors

The effects of geometrical and rotational isomerism on two-photon absorption (TPA) for several X-shaped molecules, each consisting of a pair of donors and acceptors, have been investigated employing the quadratic response theory with both the B3LYP and CAM-B3LYP functionals. The solvent effects on the simulated spectra are considered by means of the polarizable continuum model (PCM). Conformational Maxwell–Boltzmann (MB) averaging is carried out for rotational isomers. Our calculations exhibit that the geometrical isomers possess quite different TPA properties including the spectral profile, peak position and intensity. The rotational isomerism has unnegligible effects on the absorption position and intensity.