The use of a molecular balance derived from 5,5′-bipyrazole to calculate π−π stacking interactions

Theoretical calculations have been carried out on 3,3′-dimethyl-1,1′-diphenyl-5,5′-bi-1H-pyrazole to evaluate its usefulness as a molecular balance to measure π−π stacking. After removing the methyl groups (1,1′-diphenyl-5,5′-bi-1H-pyrazole), the N-phenyl groups have been replaced by a series of aromatic rings, and the energy difference between the syn and anti forms is discussed in terms of π−π stacking and dipole–dipole interactions.