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 x 10(3) and 6.3-49.1 x 10(3), respectively, in GPC analysis. Fully soluble polymers gave [eta] 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.