Spectroscopic Study of Hydrogen Bonded7‐Azaindole Clusters

The geometric structures of 7-azaindole (7-AzI) and its dimer were investigated by laser-induced fluorescence (LIF). The rotationally resolved LIF spectrum (resolution: ∼0.00003 cm -1 of 7-AzI monomer shows that (i) rotational constants are A′′ 0.13082(5), B′′ = 0.05677(2), C′′ = 0.03970(1), A′ = 0.12468(5), B′ = 0.056752(2), and C′ = 0.03911(1), and (ii) the transition dipole moment direction is tilted at an angle of ± 21(5) degrees with respect to a axis. The LIF spectrum (resolution: ∼0.06 cm -1 ) of the nonreactive 7-AzI dimer suggests there are three possibilities for the geometric structure, having “single bonded”, “T-shaped”, and “non-planar” structures. The ionization energy of 7-AzI was determined to be 8.1171(5) eV by using pulsed-field ionization photoelectron spectroscopy (PFI-PES). Several vibronic bands of 7-AzI cation were observed and compared with those of neutral 7-AzI in the S 0 and S 1 states. The electron binding energies of 7-AzI cluster anions (2 ≤ n ≤ 5) were determined by photoelectron spectroscopy.