Effect of pressure on charge transfer complexes in solution

The stability constants and absorption coefficients of π-π charge transfer complexes were measured in solution at pressures up to 6000 atm. The donors used were hexamethylbenzene, benzene, napthalene, anthracene, and pyrene, the acceptors tetracyanoethylene, s-trinitrobenzene, 2,4,6-trinitrochlorobenzene, and chloranil. The stability constants increased with pressure in every case and the volumes ΔV of formation of the complexes from their components, varied between –2 and –12 ml mole–1. The pressure changes in K and hvCT can be interpreted in terms of shortening of the charge-transfer bond. For complexes of known crystal structure values of ΔV calculated for the solid agree with the values found in solution.