The structural and photophysical properties of multibranched derivatives with curved conjugated aromatic cores†
The goal is to search for more efficient as well as more practical nonlinear optical (NLO) chromophores. Two series of three-dimensional NLO chromophores with five substituted branches and curved conjugated frameworks as the central coupling unit were investigated in the present work. Curvature of the central core plays an important role in determining the electronic structure and physical properties of multibranched conjugated π bowl derivatives. Compared to dipolar and octupolar NLO chromophores, multibranched conjugated π bowl derivatives have a different origin of the NLO response and exhibit considerable β values in both hyper-Rayleigh scattering and electric field-induced second harmonic generation processes due to effective dipolar and octupolar contributions. Additionally, multibranched conjugated π bowl derivatives can be easily assembled in a highly ordered manner due to their permanent dipole moments. A cooperative effect in the crystal will significantly enhance the macroscopic NLO response of the molecular crystal due to intermolecular dipole interactions among monomers.