Synthesis and Chemical Properties of π-Conjugated Zinc Porphyrin Polymers with Arylene and Aryleneethynylene Groups between Zinc Porphyrin Units

Organometallic polycondensation gave zinc porphyrin (Por) polymers (e.g., (−Ar−Por-Ar−) n and (−C⋮C−Por-C⋮C−Ar−) n; Ar = arylene) having arylene or aryleneethynylene groups between the zinc porphyrin units. Polymers having long alkyl substituent(s) in the Ar unit were soluble in THF and chloroform, and gave M n and M w values of 4.6−37.9 × 10 3 and 6.3−49.1 × 10 3, respectively, in GPC analysis. Fully soluble polymers gave [η] values of 0.21−0.35 dL g -1 . All of the zinc porphyrin polymers showed absorption peaks in regions of the Soret and Q-bands, respectively, in chloroform solution and as cast films, and the shift and splitting of the absorption peaks depended on the Ar and −C⋮C−Ar−C⋮C− groups. They exhibited photoluminescence in chloroform. Powder X-ray diffraction patterns of the polymers indicated that the polymers bearing long alkyl chain(s) in the spacing Ar group formed an ordered structure in the solid state. Free-standing films were obtained by casting. Films of polymers on a Pt plate were electrochemically active and showed electrochromism. Comparison of the optical properties of the polymers with those of model compounds, Ar‘-⋮-Por-⋮-Ar‘ (Ar‘ = phenyl or thiophene-2-yl), was also carried out.