Synthesis and characterization of 9-phenylcarbazole monodendrons: an exploration of peripheral groups to facilitate purification

9-Phenylcarbazole ethynylene monodendrons with 1,1,3,3-tetramethylbutyl and 3,5-di-tert-butyl-4-(2-methoxyethoxy)phenylene groups were synthesized. Both peripheral groups increased the solubility of the monodendrons. Only three generations of monodendrons with 1,1,3,3-tetramethylbutyl peripheral groups were realized due to difficulties in the purification of monodendron 31-mer. A peripheral monomer with two 3,5-di-tert-butyl-4-(2-methoxyethoxy)phenylene groups at the 3- and 6-positions of carbazole increases the solubility as well as the polarity of the monodendrons so as to facilitate the separation by adsorption chromatography, thereby enabling monodendrons up to generation four (MW = 16.6 kDa) to be realized. A monomer bearing a 3-hydroxy-3-methyl-but-1-ynyl group at its focal point as a masking group for terminal acetylene functionality was used to facilitate the removal of diacetylene byproducts.