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

Abstract

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 Mn and Mw values of 4.6−37.9 × 103 and 6.3−49.1 × 103, 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.