Some new nitrogen bridgehead heterocyclic cyanine dyes

New monomethine, trimethine, and azomethine cyanine dyes of pyrazolo[4',5': 5,6] (pyrazinio/1,4-oxazinio) [2,3,4-i,j]quinolin-11-ium bromides were prep ared. These cyanines were identified by elemental and spectral analyses. Th e visible absorption spectra of some selected dyes were investigated in sin gle and mixed solvents, and also in aqueous buffer solutions. The spectral shifts are discussed in relation to molecular structure and in terms of med ium effects. Molecular complex formation with DMF was verified through mixe d-solvent studies.