Preparation and emission properties of various poly(dimethylsilylenearylenevinylene)s: Effects of geometric structures and π units on their emission properties

trans-Poly(dimethylsilylenearylenevinylene)s (trans-rich) and cis-poly-(dimethylsilylenearylenevinylene)s (cis-rich) containing phenylene, biphenylene, and phenylenesilylenephenylene units were prepared by hydrosilylation catalyzed with the RhI(PPh₃)₃ complex. The addition of a phenylene π unit to poly(silylenephenylenevinylene) expanded the conjugation in the main chain, whereas the insertion of a dimethylsilylene σ unit in the biphenylene moiety reduced the conjugation. UV spectra of the trans-type polymers showed redshifts and hyperchromic effects with respect to those of the cis-type polymers, indicating wider conjugation, and the quantum yields of emission of the former polymers were much higher than those of the latter polymers. The quantum yield of the trans-rich polymer with the biphenylene moiety reached 0.15, which was about 10² times as large as those of trans-type polymers with phenylene (3.4 × 10^-3) and phenylenesilylenephenylene (1.9 × 10^-3) moieties. The effects of the geometric structure and π unit on the absorption and emission properties of these polymers were examined with molecular orbital methods.