Effect of ring annelation on Li+–benzene interaction: A computational study

Calculations at the B3LYP functional and MP2 method using 6-31G(d,p) basis set reveal that binding affinity of Li+ ion with benzene is enhanced by tri-annelation of benzene or highly strained bicyclo[2.1.1]hexene ring. The substantial increase of interaction energy of benzene–Li+ complex by ring annelation of bicyclo[2.1.1]hexene may be attributed to the weak C–H ⋯ Li+ interactions in addition to Li+–π interaction. Annelation of three bicyclo[2.1.1]hexene rings to benzene yields a good receptor for cation binding. The binding of Li+ with ring annelated benzenes has significant impact on the characteristic vibrational frequencies and NMR chemical shifts.