Library Of Fluorescent Polysulfonamides And Polyamide Synthesized By Iridium-Catalyzed Direct C-H Amidation Polymerization

Step-growth polymerization via C-H activation is an attractive technique due to its advantages such as atom- and step economy, derived from the reduced the number of synthetic steps required for the overall process and elimination of organometallic byproducts. To expand the utility of C-H activation polymerization beyond C-C bond coupling, we recently developed a highly efficient direct C-H amidation polymerization (DCAP) involving C-N bond formation, as a green polymerization process for synthesizing polysulfonamides. Here, we present a full account of the use of DCAP in the preparation of a library of polysulfonamides and polyamide from various diamides and diazides. From extensive model studies, several directing groups were screened, and it was found that subtle design of the directing groups by altering the steric hindrance and chelating bond angle greatly affected the efficiency of C-H amidation. Five directing groups were selected and seven AA-type monomers and seven BB-type monomers of azides were designed. After optimizing the polymerization process, 25 examples of well-defined high-molecular-weight (up to 171.4 kDa) polysulfonamides and polyamide were prepared. Notably, even diamide monomers containing four reactive ortho-C-H bonds produced defect-free polysulfonamides without cross-linking, supported by H-1 NMR spectroscopy and size exclusion chromatography (SEC) traces. Furthermore, many of these polysulfonamides emitted light via an excited-state intramolecular proton transfer (ESIPT) process as a result of tautomerization upon photoexcitation.