| Popis: |
Various methods of determination of the dihedral angle θ in biphenyl derivatives are described. A comparison is established by using former results and by interpreting new experimental results from work on eight biphenyl derivatives: C 12 H 10 ; 4-C 12 H 9 F; 4-C 12 H 9 Br; 4,4′-C 12 H 8 F 2 ; 4,4′-C 12 H 8 Br 2 ; 4,4′-C 12 H 8 Cl 2 ; 4-C 12 H 9 CN and C 12 F 10 . Benzene derivatives (C 6 H 6 , C 6 H 5 F, C 6 H 5 Br and C 6 H 5 CN) and fluorene (C 13 H 10 ) are used as model compounds. Electro-optical measurements and Raman intensities in the 1600 cm −1 region give a quantitative estimate of θ in solution. Three other spectroscopic methods have been tested in order to compare values of θ in solution and in the solid state. They are based on the number of infrared and Raman bands, the changes in intensity of specific infrared bands and the frequency shifts of infrared and Raman bands. The first two methods give qualitative results while the last gives an estimation of the variation of θ between both phases. |
