tetrahydro(5)helicene unit: synthesis, characterization, electrochemical behavior, and comparison with a linear oligoimide analogue

Herein, we describe the synthesis, characterization, and electrochemical behavior of dendritic aryl imides derived from a core compound 3,12-dinitro-5,6,9,10-tetrahydro(5)helicene-7,8-dicarboxylic anhydride ( 3). Compound 3 is an AX2 type system (where X is a masked or protected group), possesses a well-defined spatial orientation, is conformationally rigid, and contains a conjugated o-terphenyl moiety as part of its molecular structure. This compound is used as a building block in the construction of dendritic aryl imides using a divergent synthetic approach. Dendrons from generations one through three were synthesized, and their identities were confirmed. A comparison of the properties of the dendrons, several model compounds, and a linear oligoimide, all containing either the tetrahydro(5)helicene or o-terphenyl units, has been made. There are differences in their hydrodynamic volume, glass transition temperature, and electrochemical behaviour. All dendrons are electrochemically active and exhibit well- defined and reversible redox cycles. Furthermore, all dendrons are fluorescent, and the intensity of the fluorescent emission is dependent on the generation of the dendron.