Vibrational study of 3,4 '-bitriazole and some of its C-monosubstituted derivatives

The vibrational study of 3,4'-bitriazole, 5-methyl-3,4'-bitriazole and 5-br omo-3,4'-bitriazole is reported and an assignment of their fundamentals is proposed on the basis of the existence of only one form in the solid state. The substitution of the hydrogen in 3 position of the {1H} triazolic ring by 4-triazolyl group induces a decrease in the strength of the NH...N hydro gen bond comparatively to 1,2,4-triazole and its C-monosubstituted derivati ves. The introduction of a substituent in position 5 of the biheterocycle i ncreases the strength of the self association mainly when the substituent i s an electron-attractor group. Using the vN-H wave number values, the estim ation of N...N distances in these derivatives is possible. The distinction between the triazolic ring' s vibrations and those of 4-tri azolyl group seems impossible, probably because of the conjugation of the t wo rings. The higher frequency value obtained for the intercyclic bond stre tching mode in the BrbTA is explained by an important conjugation and a sho rter C-N bond in this case.