Laser-induced fluorescence spectra of 7-azaindole center dot center dot center dot formamide complex are measured in a supersonic free jet expansion. Calculation at MP2/6-311++G** level predicts a cyclic doubly hydrogen-bonded structure for the complex is favoured most in the ground state. The complex emits only UV fluorescence from the locally excited state and tautomerization is inhibited under the jet-cooled environment. This photophysical behavior is consistent with the predictions of CIS/6-311++G** and TDDFT/6-311++G** calculations. The low-frequency bands in the fluorescence spectra are assigned to different hydrogen bond modes of the complex, and the spectra reveal signatures of mixing between inter-and intra-molecular vibrational modes in the excited state. (C) 2011 Elsevier B.V. All rights reserved.