Vibrationally resolved electronic spectroscopy and theoretical studies of deuterated 2-(2′-pyridyl)indole

Laser induced fluorescence (LIF) and mass-selected (m/dm = 430) resonance two-photon ionization (R2PI) methods were employed to study the effect of deuterium for hydrogen (D/H) substitution in 2-(2′-pyridyl)indole (PyIn-0). Under the experimental conditions applied two hydrogen atoms have been exchanged. We have detected and identified four different D/H isotopomers of PyIn-0. The most reactive site for D/H substitution in PyIn-0, other than N1–H, was assigned to the pyrrole C3–H. By a combination of density functional theory (DFT) and ab initio calculations the spectroscopic shifts have been reproduced in good agreement with the experiment. A ZPVE scaling factor of 0.9849 at the B3LYP/6-31G(d,p) level has been proposed.