Synthesis and solvatochromism of some dipolar aryl-phosphonium and -phosphine oxide systems

The synthesis is reported of a series of dipolar arylphosphonium salts bearing ferrocenylethenyl, 2-thienylethenyl, 4-dimethylaminophenylethenyl, or (4-dimethylaminophenyl)butadienyl electron-donor centres, together with a study of their course of alkaline hydrolysis, which provides a convenient synthetic route to related dipolar phosphine oxides. The phosphonium salts exhibit a modest degree of negative solvatochromism, whereas the related phosphine oxides show a small positive solvatochromic effect. In the case of the ferrocenyl systems, the electronic effects of the phosphorus acceptor group on the ferrocene unit have been studied by cyclic voltammetry. (C) 2000 Elsevier Science S.A. All rights reserved.