Synthesis and properties of novel through-space π-conjugated polymers having [2.2]paracyclophane in the main chain

摘要

[2.2]Paracyclophane, in which two benzene rings are close to each other and facing, is attracted to the structure, reactivity, and physical properties. A number of paracyclophane derivatives have been prepared, and their physical properties, especially optical and electronic properties due to the characteristic interactions between the two co-facial π-electron systems, have been investigated. In addition, several polymers having paracyclophane in the main chain (in the course of developing new processes for cross-linking resins) or in the side chain and oligothiophene-substituted polymers with a [2.2]paracyclophane core have been studied so far. In 1986, Mizogami and Yoshimura reported the first synthesis of polymetacyclophane by polycondensation reaction of an oxidative dimer of 8,16-dihydroxy[2.2]metacyclophane, which exhibited a conductivity of 0.25 S cm~(-1) by doping with H_2SO_4 vapor. However, no well-defined π-conjugated polymers using the longitudinal π-π interaction of paracyclophane as a repeating unit have yet been reported. On the other hand, the synthesis of novel π-conjugated polymers have received extensive attention due to their unique optical, electrochemical, and nonlinear optical properties. [2.2]Paracyclophane seems to be a promising candidate for the aryl unit of π-conjugated polymers, e.g., poly(phenylene-ethynylene) and poly(phenylenevinylene). Here, we report on the first preparation and physical properties of novel π-conjugated polymers based on poly(p-phenylene-ethylene)s (PPEs) and related [2.2]paracyclophane-containing polymers via the through-space having a [2.2]paracyclophane skeleton in the main chain.