Molecular motion in solid π–π molecular complexes. Part 3.—Pulse n.m.r. measurements on solid charge-transfer complexes of naphthalene and pyrene

Abstract

Pulse n.m.r. techniques have been used to measure the temperature dependence of T₁ and T_1ρ for the proton resonances of the π–π molecular complexes of the donor molecules naphthalene and pyrene with the acceptor molecules tetracyanoethylene, tetracyanobenzene, and pyromelitic dianhydride in the solid state. The results confirm the existence of various molecular motions in these complexes and yield accurate activation parameters for them. Theoretical calculations of the energy barriers using semi-empirical non-bonded interatomic potential functions have also been made. Both sets of results are compared with the available literature data from wide-line n.m.r. and X-ray crystallographic investigations.