Effect of pressure on charge transfer complexes in solution

Abstract

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 hv_CT 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.