A study of N,N-dicarboxyalkylthiacarbocyanines as cyanine direactive dyes covalently bound to cellulose

The synthesis of N,Nʹ-dicarboxyalkylthiacarbocyanines and their spectroscopic properties before and fixation to microcrystalline cellulose are described. Fixation yields were determined by FTIR spectroscopy, giving an alternative to the classical indirect spectroscopic method that uses the ratio of the areas of the absorption bands for cellulose and fixed dye. Diffuse reflectance spectrometry was used to compare chemically bound dye on cellulose to physically adsorbed dye. These results, in tandem with laser induced fluorescence emission data, revealed the formation of aggregates and considerable molecular distortion, the latter resulting from a decrease in molar absorptivity compared to the case in which the dye is physically absorbed.