Spectroscopic Characterization of Hydrogen‐Bonded 2,7‐Diazaindole‐Ammonia Complex: Laser Spectroscopic Investigations of Isolated Gas Phase Molecules

We present the vibrationally resolved two‐color resonant two‐photon ionization (R2PI), laser induced fluorescence (LIF), single vibronic level fluorescence (SVLF), and isomer‐selective fluorescence dip infrared spectroscopy (FDIR) of 2,7‐diazaindole‐ammonia (27DAI‐NH3) complex seeded in a supersonic jet. The vibrational band due to internal translation of ammonia molecule in the complex appeared at 169 and 182 cm−1 in the ground and excited state, respectively, suggesting a stronger hydrogen bonding interaction upon electronic excitation.The ground state structure of the complex was obtained using the FDIR spectrum with four bands observed at 3240, 3304, 3403, and 3433 cm−1, which showed a good agreement with the vibrational frequencies of the most stable structure.‐ The νN(1)─H frequency of the complex at 3240 cm−1 showed a significant red shift of 283 cm−1 to that of the 27DAI monomer, suggesting a strong N(1)─H⋯N interaction in the complex. Further, the vN(1)─H value of 27DAI‐NH3 complex provided a blue shift of 15 cm−1 compared to 7AI‐NH3 complex, implying a weakening of the N(1)─H⋯N hydrogen bonding interaction due to N(2) insertion. The current investigation also revealed that in the ground electronic state, the N(2) insertion makes 27DAI molecule a weaker hydrogen bond donor and acceptor compared to that of the 7AI molecule.