Effect of the end-groups upon delocalisation in polymethines: the first crystallographically characterised bond-alternated cyanine

Abstract

The reorganisation energy associated with the end groups may be used to influence the localisation behaviour of cyanines; thus, the 1,3-bis(ruthenocenyl)allylium cation is markedly unsymmetrical in the crystal structure of its hexafluorophosphate salt, with the positive charge localised on one ruthenium, whereas the analogous iron species is delocalised and has approximate C₅ symmetry.