Features of the C-H center dot center dot center dot N Weak Hydrogen Bond and Internal Dynamics in Pyridine-CHF3

The dynamics, location, and hydrogen-bond features of CHF3 change drastically on going from the benzene-CHF3 to the pyridine-CHF3 molecular adduct. The barrier to internal rotation increases from almost nothing to ?0.6 kJ mol-1; the CHF3 moiety moves into the ring plane from above, and a C[BOND]H???N linkage replaces the C[BOND]H???? contact (see figure).