Synthesis of porphyrin-end-functionalized poly(p-phenylene) as a leaf-green-colored soluble semiconducting polymer: Control of π–π interactions for visible-light absorption

Abstract The synthesis of tetraphenylporphyrin (H 2 TPP)-end-functionalized poly( p -phenylene) (H 2 TPP-PPP) as a leaf-green-colored soluble semiconducting polymer with a well-controlled and defined polymer chain structure was achieved for the first time. Chloromethyl-end-functionalized poly(1,3-cyclohexadiene) (CM-PCHD) was prepared by the living anionic polymerization of 1,3-cyclohexadiene and the post-polymerization reaction of poly(1,3-cyclohexadienyl)lithium and chloro(chloromethyl)dimethylsilane. H 2 TPP-end-functionalized PCHD (H 2 TPP-PCHD) was then prepared by the addition of 5-(4-hydroxyphenyl)-10,15,20-triphenylporphyrin to CM-PCHD. The dehydrogenation of H 2 TPP-PCHD with 2,3-dichloro-5,6-dicyano-1,4-benzoquinone was performed under ultrasonic irradiation, and H 2 TPP-PPP was obtained as a target polymer in almost quantitative yield. The –Si(CH 3 ) 2 –CH 2 –O– bond in H 2 TPP-PPP effectively inhibited the coordination of the H 2 TPP end-group onto the PPP moiety, and the aggregation of H 2 TPP-PPP with the accumulation of the H 2 TPP end-group was formed. H 2 TPP-PPP exhibited a leaf-green color and had a very broad absorption band overlapping the visible-light region, similar to chlorophyll a.