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

The synthesis is reported of a series of dipolar arylphosphonium salts bear ing ferrocenylethenyl, 2-thienylethenyl, 4-dimethylaminophenylethenyl, or ( 4-dimethylaminophenyl)butadienyl electron-donor centres, together with a st udy of their course of alkaline hydrolysis, which provides a convenient syn thetic route to related dipolar phosphine oxides. The phosphonium salts exh ibit a modest degree of negative solvatochromism, whereas the related phosp hine oxides show a small positive solvatochromic effect. In the case of the ferrocenyl systems, the electronic effects of the phosphorus acceptor grou p on the ferrocene unit have been studied by cyclic voltammetry. (C) 2000 E lsevier Science S.A. All rights reserved.