Dye spectra of benzene derivatives in the liquid-crystalline phase of 4-n-pentyl-4΄-cyanobiphenyl.

In the present paper, we study the interaction of associates (dimers and trimers) of 4-n-pentyl-4΄-cyanobiphenyl (5CB) with 1, 2-Diamino-4-nitrobenzene and N, N-Dimethyl-4-nitrosoaniline dye molecules. The structures of the intermolecular complexes were studied using hybrid functionals of the DFT method M06 and B3LYP with the 6-31 + G (d) basis set. The intermolecular binding energy of dyes with associates depends on the structure of the complexes and is about 5 kcal/mol. Vibrational spectra were calculated for all intermolecular systems. The electronic absorption spectra of dyes are sensitive to the structure of the mesophase. The pattern of the spectrum changes depending on the structure of the complex of the dimer or trimer with the dye molecule. The long-wavelength transition bands are characterized by shifts that are bathochromic for 1, 2-Diamino-4-nitrobenzene and hypsochromic for N, N-Dimethyl-4-nitrosoaniline.