The Effect of Branching on One‐ and Two‐Photon Absorption, Cell Viability and Localization of Cationic Triarylborane Chromophores with Dipolar vs. Octupolar Charge Distributions for Cellular Imaging†

Two different chromophores, namely a dipolar and an octupolar system, were prepared and their linear and non-linear optical properties as well as their bioimaging capabilities were compared. Both contain triphenylamine as the donor and a triarylborane as the acceptor, the latter modified with cationic trimethylammonio groups to provide solubility in aqueous media. The octupolar system exhibits a much higher two-photon brightness, and also better cell viability and enhanced selectivity for lysosomes compared with the dipolar chromophore. Furthermore, both dyes were applied in two-photon excited fluorescence (TPEF) live-cell imaging.