End Functionalization of Polynorbornene with Platinum-Acetylide Complexes Utilizing a Cross-Metathesis Reaction

The functionalization of the chain end of a polymer is gathering increasing attention in the field of synthetic polymer chemistry. The present study is the first example to demonstrate the incorporation of a platinum-acetylide complex at the terminal of a polynorbornene derivative. N-Benzyl-5-norbornene-2-exo,3exo-dicarboxyimide (1) was polymerized with Grubbs 3rd generation catalyst (G3). The polymerization was quenched with (Z)-1,4-bis(3-((trimethylsilyl)ethynyl)phenoxy)-2-butene (2) to obtain poly(1)', followed by the cleavage of trimethylsilyl group and dehydroiodination coupling with trans-bis(tributylphosphine)phenylethynyl iodo platinum (3a) to obtain poly(1a), which was functionalized with a platinum complex at the chain end. Poly(1)' exhibited no remarkable absorption around 330 nm, while poly(1a) exhibited an intense absorption based on ligand-to-metal charge transfer transition. Poly(1b) functionalized with a naphthylamide ethynyl platinum complex was synthesized in a similar fashion. The photoluminescene color of a poly(1b) solution in CH2Cl2 changed from green to red with Ar bubbling and rapidly returned to green by ceasing Ar bubbling. A poly(1b)-containing polymethyl methacrylate film exhibited a similar trend, as was observed for the polymer in solution. The weight residues of poly(1a) and poly(1b) at 800 degrees C were higher than that of poly(1).

Automated summary

The functionalization of polymer chain ends is a hot topic in synthetic polymer chemistry. This study demonstrates the incorporation of a platinum complex at the terminal of a polynorbornene derivative for the first time. The modified polymers exhibited enhanced absorption and photoluminescence properties compared to the unmodified polymer. The weight residues of the functionalized polymers at high temperatures were higher than the unmodified polymer.