Terahertz spectroscopy of 7-azaindole clusters in solution

The terahertz spectrum of 7-azaindole in solution has been obtained from 5 to 165 cm−1 and analyzed using density functional theory calculations. The experimental spectrum exhibits a strong absorption feature at 76 cm−1 that is attributed to an intermolecular vibration of self-associated 7-azaindole dimers. The calculations reveal that observed spectral features, which are unaccounted for in the 7-azaindole dimer normal mode analysis, may be attributed to a 7-azaindole hydrogen-bonded tetramer. This work presents the first quantum mechanical investigation of the structure and low-frequency vibrational motions of the 7-azaindole tetramer.