Orientation and alkylation effects on cation-pi interactions in aqueous solution.
We have investigated the orientation dependence of the cation-pi interaction between a phenyl ring and a pyridinium ring in the context of a flexible model system in water. Of the four possible positions of the pyridinium nitrogen, ipso, ortho, meta, and para, we found a variation in the interaction energy of about 0.75 kcal mol(-1), with the stacking of the ipso-pyridinium ring providing the strongest interaction. The observed stability is attributed to the maximization of the electrostatic interaction, minimization of rotamers, and possible differences in hydration phenomena arising from alkylation.
Department of Chemistry, CB 3290, University of North Carolina, Chapel Hill, North Carolina 27599, USA.
Mark J
MJ
Rashkin
Robert M
RM
Hughes
Nathaniel T
NT
Calloway
Marcey L
ML
Waters