Computational study of red- and blue-shifted Csingle bondH⋯Se hydrogen bond in Q3Csingle bondH⋯SeH2 (Q = Cl, F, H) complexes

Abstract

This work presents Csingle bondH⋯Se hydrogen bonding interaction at the MP2 level of theory. The system Q3Csingle bondH⋯SeH2 (Q = Cl, F, and H) provides an opportunity to investigate red- and blue-shifted hydrogen bonds. The origin of the red- and blue-shift in Csingle bondH stretching frequency has been investigated using Natural Bond Orbital analysis. A large amount of electron density is being transferred to the σ∗Csingle bondH orbital in red-shifted Cl3Csingle bondH⋯SeH2. Electron density transfer in the blue-shifted F3Csingle bondH⋯SeH2 is primarily to the remote fluorine atoms. Further, due to polarization of the Csingle bondH bond, the contradicting effects of rehybridization and hyperconjugation are important. The extent of hyperconjugation reigns predominant in explaining the nature of the Csingle bondH⋯Se hydrogen bond in Q3Csingle bondH⋯SeH2 complexes as the hydrogen bond acceptor remain same in this investigation. Red- and blue-shift in Q3Csingle bondH⋯SeH2 (Q = Cl and F) complexes is best described by pro-improper hydrogen bond donor concept.