A novel method of synthesizing long-wavelength absorbing and emitting bis-trimethine dyes that consists of condensing benzodipyrrolenine dialdehyde with quaternized heterocyclic CH-acidic compounds was used to prepare a series of biscyanines. The new method is more convenient than its conventional counterepart, which relies upon condensation of a quaternized benzodipyrrolenine with Fisher's aldehyde, for the synthesis of a ...