Competition between dihydrogen bond and beryllium bond in complexes between HBeH and HArF: A huge blue shift of distant HAr stretch

A novel interaction mechanism between HArF and BeH2 has been validated and characterized with quantum chemical calculations at the MP2/aug-cc-pVQZ level. They can interact through beryllium bonding formed between the positively charged Be atom in BeH2 and the negatively charged F atom in HArF, besides through dihydrogen bonding. The former (61.3 kcal/mol) is much stronger than the latter (5.9 kcal/mol). The red shift is found for the associated HAr stretch in the dihydrogen bonding, whereas the big blue shift is observed for the distant HAr stretch in the beryllium bonding. The blue shift of the distant HAr stretch is affected greatly by computational methods. It is calculated to be 712 cm−1 at the CCSD(T)/6-311++G(3df,2p) level, which appears to be the largest blue shift validated for any weakly bound complex yet. The substitution effect on the beryllium bond is similar to that on hydrogen bonds. The Kr atom makes the beryllium bond weaken and the distant blue shift decrease. The nature and properties of beryllium bond have been analyzed with natural bond orbital (NBO), atoms in molecules (AIM), and energy decomposition.

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► Beryllium bonding is a dominant mode in the complexes of HArF and BeH2.
► The HAr stretch vibration shows a big blue shift in the beryllium bond.
► The beryllium bond is dominated with an electrostatic interaction.
► HKrF forms a weaker beryllium bond than HArF counterpart.