Features of the chemical structure of ?,?-difluorostilbenes

Sulfur as a Structural Element in Calamitic Liquid Crystals. 2 Terminal, Linking, Axial and Lateral Substitutions. 3 Sulfur-Containing Rings

“…(2) and the previous section, it follows that compounds that have a large induced polarizability of their highly conjugated p-electron system (for example, isothiocyanato derivatives) exhibit an optical anisotropy Dn ¼ n e À n o that is much larger than that of the corresponding halogen(s)-substituted derivatives (compounds 2-3 to 2-8, 2-11, 2-14; 5-1, 5-2; 6-12 to 6-16; Tables 2, 5, 6, [52]). A decrease in optical anisotropy for compounds with the halogenated terminal, linking, and lateral groups (Tables 2, 4 -6, 9-11, 13) can be explained in terms of a reduction in the effective conjugation of the p-electron system resulting in a shorter resonance wavelength of the UV absorption spectrum for the halogen(s)-substituted liquid crystals than for the corresponding parent compounds or having hydrogenated groups [52,[138][139][140][141]. The axial and lateral NCS substitutions do not contribute so much to the optical anisotropy of liquid crystals (Tables 10 and 11) and work as usual lateral substitutions [87].…”

Halogenation in Achiral Calamitic Liquid Crystals. II Terminal and Linking Substitutions

“…Tables 2 and 3 show that the halogenated compounds exhibit similar values of optical anisotropy (Dn ¼ n e -n o ) to those of other halogenated LCs presented in [1]. While, a decrease in optical anisotropy for compounds with the fluorinated linkages (compounds 4-1, 4-2, 4-3, 4-6-4-8, Tables 4-6) can be explained in terms of a reduction in the effective conjugation of the p-electron system resulting in a shorter resonance wavelength of the UV absorption spectrum for linking halogen(s) substituted liquid crystals than for the corresponding parent compounds or having hydrogenated linkages [1,[189][190][191][192].…”

Effect of the fluorine substitution in ethyl groups of 1,4-distyrylbenzene on the fine structure fluorescence and fluorescence excitation spectra

“…In studies of α,ω difluoro substituted derivatives of stil bene and diphenylbutadiene [3][4][5], it was noted that, upon fluorine substitution, the absorption and fluores cence band maxima are hypsochromically shifted by 10 and 30 nm, respectively.…”