The effect of the amino group on the spectral properties of substituted styrylpyridinium salts

Thirty-six trans-1-methyl-2- and -4-(p-aminostyryl)pyridinium perchlorates were obtained by the condensation of dimethylpyridinium salts with p-aminobenzaldehydes. In all cases, a strong absorption band was present in their UV/VIS spectra above 400 nm. The spectral parameters were not simply related to the substituent constants of the amino groups. A comparison with the respective styrylpyridinium iodides showed the anion to have no effect on the spectra. The 1-methyl-(p-aminostyryl)pyridinium salts prepared are expected to be useful materials in non-linear optics and in biological studies.