Branching of Substituted Push-Pull Polyenes for Enhanced Two-Photon Absorption

The paper will focus on the branching of substituted push-pull polyenes in the weak to medium interaction limit. Branching of dipolar units of increasing length is achieved through connection via a central triphenylamine core, leading to three-branched structures. Linear and nonlinear optical properties of these octupolar chromophores are compared to those of their dipolar analogues. In particular, photophysical properties, solvatochromism and two-photon absorption (TPA) cross sections are investigated. Results confirm that the branching strategy leads to TPA activation in spectral regions were the dipolar units are almost transparent and that large TPA enhancement can be achieved on a very large spectral range. Localization of the emitting excited state on a single dipolar branch is also evidenced.