Experimental Study of the Cooperativity of CH−π Interactions

A series
of new torsional molecular balances was designed to study
the cooperativity of CH−π interaction in the solid state
and in solution. The measured interaction energies correlated better
to the number of participating alkyl carbons than to the number of
CH−π contacts. The methyl and ethyl groups displayed
additive interaction energies. However, the branched isopropyl group
displayed strong positive cooperativity with higher than predicted
interaction energies.