Photoinduced [6π]-Electrocyclic Reaction of Mono-, Di-, and Trisubstituted Triphenylamines in Acetonitrile. A Steady-State Investigation

Perfluoroalkylation of Triarylamines by EDA Complexes and Ulterior Sensitized [6π]-Electrocyclization to Perfluoroalkylated Endo-Carbazoles. Mechanistic and Photophysical Studies

Blue LEDs-irradiation of a mixture of N,N,N',N'-tetramethylethylenediamine (TMEDA) and perfluoroalkyl iodides (RF-I) - Electron Donor Acceptor (EDA)-complex - in the presence of triphenylamines (TPAs) in an aqueous solvent mixture afforded mono-perfluoroalkylated triphenylamines (RF-TPA) in good yields. These RF-TPA were further subjected to acetone-sensitized [6π]-electrocyclization at 315 nm-irradiation affording exclusively perfluoroalkylated endo-carbazole derivatives (RF-CBz) in quantitative yields. Mechanistic studies and photophysical properties of products are studied.

A Rational Design of Electrochemically and Photophysically Tunable Triarylamine Luminophores by Consecutive (Pseudo-)Four-Component Syntheses

The concatenation of Suzuki coupling and two-fold Buchwald-Hartwig amination in sequentially palladium-catalyzed consecutive multicomponent syntheses paves a concise, convergent route to diversely functionalized para-biaryl-substituted triarylamines (p-bTAAs) from simple, readily available starting materials. An extensive library of p-bTAAs permits comprehensive investigations of their electronic properties by absorption and emission spectroscopy, cyclic voltammetry, and quantum chemical calculations, which contribute to a deep understanding of their electronic structure. The synthesized p-bTAAs exhibit tunable fluorescence from blue to yellow upon photonic excitation with quantum yields up to 98 % in solution and 92 % in the solid state. Furthermore, a pronounced bathochromic shift of the emission maxima by increasing solvent polarity indicates positive emission solvatochromism. Aggregation-induced enhanced emission (AIEE) in dimethyl sulfoxide (DMSO)/water mixtures causes the formation of intensely blue fluorescent aggregates. Cyclic voltammetry shows reversible first and second oxidations of p-bTAAs at low potentials, which are tunable by variation of the introduced para substituents. 3D Hammett plots resulting from the correlation of oxidation potentials and emission maxima with electronic substituent parameters emphasize the rational design of tailored p-bTAAs with predictable electrochemical and photophysical properties.