Characterization and Minimization of Glaser Competitive Homocoupling in Sonogashira Porphyrin-Based Polycondensation.

A porphyrin-containing polymer exhibiting various degrees of Glaser-Hay coupling is reported. Sonogashira polycondensation of zinc(II) (5,15-bis[3,4,5-tri(2-butyloctyl)phenyl]-10,20-bis(ethynyl)porphyrinate) with N, N'-bis( p-iodobenzene)-2,3,5,6-tetrafluorobenzoquinone-1,4-diimine (fQI) is found to be prone to homocoupling, a problem underestimated in the literature. 1H NMR and photophysical analysis are used to assess the ratio of Glaser versus Sonogashira couplings. Optimized conditions to perform Glaser-free Sonogashira polycondensations are provided, and the optimization increases Mn from 9700 to 18 900. Applied to a conjugated polymer, it shows both decreasing homocoupling and 180% enhancement in Mn.