Spectral studies and normal coordinate analysis of some symmetric 1,5-diaryl-3-cyanoformazans

The 1,5-diaryl-3-cyanoformazans were prepared and subjected to IR, MS, H-1 NMR, and C-13 NMR spectral analysis. The results indicate the presence of a strong intramolecular hydrogen bond in the formazan molecule. Moreover, th e two phenyl rings are equivalent and the C=N and N-H stretching vibrationa l modes are slightly affected with electron-withdrawing substituents and in teract with the neighboring C-C stretching mode. The syn, s-cis formazan fo rm was supported by calculating the frequencies, normal coordinate analysis , force constant refinement, and group theory treatment. High quality of fi tting between the experimental and calculated frequencies with all formazan s has been achieved. (C) 1999 Academic Press.