A Noncovalent Binding Strategy to Capture Noble Gases, Hydrogen and Nitrogen

A molecular design strategy to develop receptor systems for the entrapment of noble gases, H 2 and N 2 is described using M06L‐D3/6‐311++G(d,p)//M06L/6‐311++G(d,p) DFT method. These receptors made with two‐, three‐, four‐ and five‐fluorinated benzene cores, linked with methelene units viz . R I , R II , R III and R IV as well as the corresponding non‐fluorinated hydrocarbons viz . R IH , R IIH , R IIIH and R IVH show a steady and significant increase in binding energy ( E int ) with increase in the number of aromatic rings in the receptor. A stabilizing “cage effect” is observed in the cyclophane type receptors R IV and R IVH which is 26–48% of total E int for all except the larger sized Kr, Xe and N 2 complexes. E int of R IV …He, R IV …Ne, R IV …Ar, R IV …Kr, R IV …H 2 and R IV …N 2 is 4.89, 7.03, 6.49, 6.19, 8.57 and 8.17 kcal/mol, respectively which is 5‐ to9‐fold higher than that of hexafluorobenzene. Similarly, compared to benzene, multiple fold increase in E int is observed for R IVH receptors with noble gases, H 2 and N 2 . Fluorination of the aromatic core has no significant impact on E int (∼ ±0.5 kcal/mol) for most of the systems with a notable exception of the cage receptor R IV for N 2 where fluorination improves E int by 1.61 kcal/mol. The E int of the cage receptors may be projected as one of the highest interaction energy ranges reported for noble gases, H 2 and N 2 for a neutral carbon framework. Synthesis of such systems is promising in the study of molecules in confined environment. © 2018 Wiley Periodicals, Inc.