Small molecular systems, such as the HCN●●●HX series (where X = F, Cl, Br, I), are particularly amenable to high-resolution, gas-phase experimental study and high-accuracy computational analysis, which can provide insight into the interplay of theory and experiment. For the complex where X = F, two different hydrogen bonded structures have been identified both experimentally and computationally: a linear structure where HF is the hydrogen bond (HB) donor and a higher-energy, non-linear (bent) structure where HF becomes the HB acceptor. We performed full-geometry optimizations and harmonic vibrational frequency computations on the remaining complexes in the series (X = Cl, Br, I) using the MP2 and CCSD(T) methods with a series of robust correlation consistent basis sets. Anharmonic corrections to the vibrational frequencies, obtained using VPT2, are being worked on using the same level of theory. For each complex, we identified both a linear and a bent hydrogen bonded structure where HX acts as the HB donor and HB acceptor, respectively. Trends in computed properties related to the HB, such as the dissociation energy and vibrational frequency shifts, will be presented for the entire series (X = F, Cl, Br, I) and compared qualitatively to published experimental and computational results.

Hydrogen bonding in the HCN●●●HX series (X = F, Cl, Br, I)

ACS Fall 2021

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