Smart Design of Highly Luminescent Octupolar Mesogenic Tetra Styryl-Alkynyl Bipyrimidine-Based Chromophores Presenting Non-Linear Optical Properties

The research investigations reported in this paper focuses on the influence of rational design on the photophysical properties of new all-organic multifunctional chromophores. Nonlinear optical (NLO) behavior, optical properties and mesogenicity of several new π-conjugated octupolar chromophores, presenting alkoxy styryl-alkynyl donor groups carrying aliphatic achiral and chiral chains in the 3,4 / 3,5 / 2,4 position, connected to electron-accepting 2,2-bipyrimidine cores are investigated by various techniques (light-transmission measurements, polarized-light optical microscopy, differential scanning calorimetry measurements, two-photon excited fluorescence and Hyper Rayleigh Scattering). The mesogenic properties were investigated depending on the position of the alkoxy chain and the 3,4 derivatives were found to exhibit liquid-crystal with the formation columnar phases over large temperature ranges which were confirmed by small-angle X-ray scattering analysis. All the molecules exhibit exceptional high fluorescence quantum yields values around 80 % and excellent nonlinear optical properties.