(Co)polymers containing boron difluoride 3-cyanoformazanate complexes: emission enhancement via random copolymerization

Ring-opening metathesis polymerization was used to produce polymers bearing an asymmetrically substituted boron difluoride 3-cyanoformazanate complex. The polymers were found to retain many of the unique characteristics of the molecular boron difluoride complexes of 3-cyanoformazanates, including intense light absorption at ca. 560 nm and reversible electrochemical reductions implicating the radical anion and dianion forms of the formazanate complexes in the repeating unit of the polymer backbone. The polymers were also found to be emissive, with emission maxima centred at ca. 665 nm. The monomer employed in this study had a fluorescence quantum yield of 30%, while homopolymers were weakly emissive and block copolymers were essentially non-emissive. The development of a monomer ‘dilution’ strategy, via random copolymerization, resulted in rejuvination of the emission at ca. 665 nm up to a maximum quantum yield of 24% when the mole fraction of the repeating units bearing boron difluoride 3-cyanoformazanate complexes (fBF2N) was 0.08.