Imine Bridged Planar Poly(p-phenylene) Derivatives for Maximization of Extended p-Conjugation. The Common Intermediate Approach

摘要

Described are two approaches to planar conjugated poly(p-phenylene) (PPP)derivatives. The first approach, involving lactam bridges, was unsuccessful due to the insolubility of the 6(511)-phenanthridinonyl moieties. The second approach, which utilized imine bridges, worked excellently since the compounds were generally soluble and the bridge formations were highly efficient. The main PPP backbone was synthesized via Pd(O)-catalyzed coupling of an arylbis(boronic ester) with an aryldibromide. Imine bridges, that are formed by exposure of the polymer to trifluoroacetic acid or HCl, force the consecutive units into planarity. The bridging units are sp2 hybridized thus allowing for greater it-electron flow between the consecutive phenyl units. The polymers, upon planarization, exhibit enormous bathochromic shifts of 210-240 nm.