Propeller-Shaped Octupolar Molecules Derived from Triphenylbenzene for Nonlinear Optics: Synthesis and Optical Studies

Abstract

Nanoscale propeller-shaped conjugated molecules based on a central triphenylbenzene core bearing three oligomeric phenylene-vinylene branches having either electron-donating or electron-withdrawing peripheral groups have been synthesized. These octupolar derivatives show definite solvatochromic behavior (in absorption and even more in emission), which reveals a multidimensional intramolecular charge transfer (MDICT) taking place between the center and the periphery of the molecules. Correlations between the solvatochromism magnitude and the nonlinear responses (first-order hyperpolarizabilities β) of such derivatives have been established. Accordingly, boosting of the MDICT phenomenon (by means of elongation of the branches and benefit from appropriate peripheral groups) allowed achievement of very high hyperpolarizabilities while maintaining wide transparency in the visible region (up to ∥β∥ = 810 × 10-30 esu for λmax = 377 nm).