Remarkably Stretched Cis–Transoid Helices Generated in Solid Phase and Solution of Poly(carbazole acetylene) Prepared Using an Organorhodium Catalyst in Toluene

Abstract

A helical π-conjugated poly(N-isobutyl-3-carbazole acetylene), P(iBCzA) was stereoregularly prepared using an [Rh(norbornadine)Cl]2–triethylamine catalyst in toluene at 25 °C to determine the detailed geometrical and spatial structures in a tetrahydrofuran (THF) solution and the solid phase. P(iBCzA), which has a bright orange color, was obtained in a yield of 90%. The 2D NMR spectrum of P(iBCzA) in THF-d8 at 50 °C indicated that an extraordinarily extended helix was produced. The WAXS pattern of P(iBCzA) showed the formation of a tetragonal crystal packed with a remarkably stretched cis–transoid (RESTCT) helix similar to that observed in the solution state. This RESTCT helix was confirmed not to be an energetically stable but a metastable structure using MMFF94 program. The solid phase UV–vis spectrum of P(iBCzA) showed the formation of a radical cation called a polaron because of the very large red shifts compared to that observed in solution without the doping.