π-Hydrogen bonding wins over conventional hydrogen bonding interaction: a jet-cooled study of indole···furan heterodimer.
In this study, we have explored the conformational landscape of the indole···furan dimer in a supersonic jet by using resonant two-photon ionization (R2PI) and IR-UV double-resonance spectroscopic techniques combined with dispersion-corrected density functional theory (DFT) calculations. Only one conformer of the dimer has been observed in the experiment. DFT/B97-D level calculation shows that N-H···π hydrogen-bonded conformer (T') is energetically more stable than the N-H···O hydrogen-bonded conformer (HB). Natural bond orbital (NBO) calculation also shows that the hydrogen-bonding interaction in the HB conformer is very weak. Finally, the structure of the observed dimer has been determined to be tilted T-shaped N-H···π hydrogen-bonded (T') from very excellent agreement between experimental and theoretical N-H stretch frequency. The most significant finding of this study is the first-time observation of a N-H···π bound conformer of a dimer, which wins over a conventional hydrogen-bonded conformer of the dimer.
Department of Chemistry, Indian Institute of Science Education & Research (IISER), 900 NCL Innovation Park, Dr. Homi Bhabha Road, Pune-411008, Maharashtra, India.
Sumit
S
Kumar
Vedant
V
Pande
Aloke
A
Das
D003080:Cold Temperature; D019281:Dimerization; D005663:Furans / Q000737:chemistry*; D006860:Hydrogen Bonding; D007211:Indoles / Q000737:chemistry*; D008968:Molecular Conformation; D015394:Molecular Structure; D011789:Quantum Theory; D019032:Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization
D005663:Furans; D007211:Indoles; C039281:furan